Biomass
as a
Renewable
Energy Source
ROYAL COMMISSION ON ENVIRONMENTAL POLLUTION
ROYAL COMMISSION ON ENVIRONMENTAL POLLUTION
Biomass as a Renewable Energy Source
About the Royal Commission on Environmental Pollution
The Royal Commission on Environmental Pollution is an independent standing body
established in 1970 to provide authoritative advice on environmental issues. Its terms of
reference are:
To advise on matters, both national and international, concerning the pollution of the environment;
on the adequacy of research in this field; and the future possibilities of danger to the environment.
Within this remit the Commission is free to consider and advise on any matter it chooses;
the UK government or the devolved administrations may also ask it to consider particular
topics.
The primary function of the Commission is to contribute to policy development in the
longer term by providing a factual basis for policy-making and debate, and setting new
agendas and priorities. It considers the economic, ethical and social aspect of issues
alongside the scientific and technological aspects. It sees its role as reviewing and
anticipating trends and developments, identifying fields where insufficient attention is
being given to environmental problems, and recommending actions that should be
taken. The Commission has published 24 reports, and many of their recommendations
have been accepted and implemented by successive governments.
The members of the Commission have a wide range of expertise and experience in natural
and social sciences, medicine, engineering, law, economics, and business. They serve parttime and as individuals, not as representatives of organisations or professions.
A full-time Secretariat supports The Chairman and Members by arranging and recording
meetings and visits; gathering and analysing information; handling finances and
administration; and drafting and publishing the Commission’s reports.
In the course of its studies, the Commission canvasses a wide range of views. Information
on its work (including minutes of meetings, background papers by consultants and
summaries of evidence submitted) is available via www.rcep.org.uk.
BIOMASS AS A RENEWABLE ENERGY SOURCE
A Limited Report by
The Royal Commission on Environmental Pollution
Contents
Page
CHAPTER 1 – Introduction
3
CHAPTER 2 – Biomass fuels
9
Energy crops
Forestry products
Sawmill co-products
Municipal arisings
Conclusions
9
21
24
26
28
CHAPTER 3 – Generation using biomass fuels
30
General principles
Heat generation
Combined heat and power
Electricity generation
Environmental implications
30
31
33
40
43
CHAPTER 4 – Meeting the target
47
Economics of biomass
Transport
Energy conversion facilities
Land-take
Planning for biomass
Phased delivery
A strategic approach
47
52
58
60
63
67
68
CHAPTER 5 – Conclusions and recommendations
69
APPENDIX A – Policies to support biomass – description of current
schemes
72
APPENDIX B – Case studies
75
APPENDIX C – Scope and limitations of the special report
83
APPENDIX D – Conduct of the report
85
APPENDIX E – Members of the Commission
88
APPENDIX F – Reports by the Royal Commission on Environmental
Pollution
89
REFERENCES
90
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
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ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
CHAPTER 1 – INTRODUCTION
Context
1.1
Energy consumption throughout the world, but particularly in industrialised societies, has
been steadily increasing. Much of the energy consumed, 97% in the case of the UK1, comes
from non-renewable sources. The present use of carbon-based non-renewable energy is
unsustainable, inter alia because of the effect of the resultant carbon dioxide (CO2)
emissions on the global climate. Reduction in demand must be part of the solution2 but
alternative energy sources must also be developed. All energy sources come with
environmental penalties, whether from the construction of dams and barriers or from the
impact of renewable sources such as wind on rural landscapes, but these impacts must be
balanced against the necessity of developing low-carbon sources that are both
economically viable and also secure.
1.2
The Royal Commission’s Twenty-second Report, Energy - The Changing Climate published
in 2000, advocated a number of steps that the government should take, both in terms of
domestic policy and through international negotiation. A key recommendation was that a
long-term target should be set to reduce CO2 emissions by 60% by 2050. This was based on
the contention that the maximum concentration of CO2 in the atmosphere should not
exceed twice the pre-industrial level. The government subsequently accepted that the UK
should put itself on a path towards this aim3. In order to reach a 60% reduction of CO2
emissions, it is vital for the government to concentrate on encouraging low- or non-carbon
electrical and heat generation. As a component of a renewable energy generation mixture,
biomass should play an important role.
1.3
There are three types of indigenous biomass fuel: forestry materials, where the fuel is a byproduct of other forestry activities; energy crops, such as short rotation coppice (SRC)
willow or miscanthus, where the crop is grown specifically for energy generation purposes;
and agricultural residues, such as straw or chicken litter. Biomass can also be imported,
mainly in the form of pelleted sawdust (which is already an internationally traded
commodity).
Why Biomass?
1.4
Wood is a renewable fuel; its production and use is almost carbon neutral. Trees absorb
CO2 to photosynthesise organic compounds using solar energy. The energy is stored
chemically and released when the wood is subsequently destroyed - whether by natural
decay or combustion. Hence, although CO2 is released into the atmosphere when wood is
burnt, an equivalent amount of CO2 has been taken from the atmosphere during growth.
Some net release of CO2 would take place if the growing, processing or transporting of the
wood involved the use of fossil fuel.
1.5
The carbon in biomass used as fuel does not therefore contribute to greenhouse gas
emissions. Technically emissions from biomass use are reported in the UK greenhouse gas
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
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inventory as a memo item, but are not included in the national total. This is in accordance
with international guidelines from the Intergovernmental Panel on Climate Change
(IPCC) and the United Nations Framework Convention on Climate Change (UNFCCC).
On the other hand emissions of nitrous oxide and methane from the combustion process
are included in the national total (because the carbon is balanced by photosynthetic uptake
but the methane and nitrous oxide are not). Emissions of nitrous oxide from any fertiliser
used to grow the biomass are also included, as are emissions of CO2 from fossil fuel used in
forest or field operations and transportation.
1.6
Unlike most other renewable energy sources biomass can be stored and used on demand to
give controllable energy. It is therefore free from the problem of intermittency, which is a
problem for wind power in particular. Also, unlike most other renewable sources, biomass
offers potential as a source of heat as well as electricity, offering high conversion
efficiencies. This potential appears to have been overlooked in government policies to
promote biomass, which have concentrated on electricity generation. In this report we
therefore concentrate on biomass as a fuel for heat or combined heat and power (CHP) . We
will show that biomass energy offers an opportunity to rethink energy generation and to
drive a step-change in the efficiency of power and heat production. The implications for the
UK’s CO2 reduction targets are highly significant.
1.7
Biomass energy technology is inherently flexible. The variety of technological options
available means that it can be applied at a small, localised scale primarily for heat, or it can
be used in much larger base-load power generation capacity whilst also producing heat.
Biomass generation can thus be tailored to rural or urban environments, and utilised in
domestic, commercial or industrial applications.
Box 1A Units of energy production
Rates of production of energy are measured in watts (or kilowatts (kW), megawatts
(MW) or gigawatts (GW)). If a production rate of one watt is maintained for one hour,
the amount of energy produced is one watt-hour.
This report uses watts and the units derived from watts to indicate energy generally.
Where it is important to distinguish heat (thermal energy) from power (electrical energy)
a suffix (th or e, respectively) is used. For example a CHP facility with a total output of 40
MW might typically produce 30 MWth and 10 MWe.
4
1.8
The technology is most efficient where a source of fuel and a demand for heat are within an
economically viable distance of each other. In this report we examine the costs of
transporting biomass fuels, both financially and in terms of CO2 emissions. We show that we
might expect a significant proportion of the UK to be able to meet the maximum distance
criterion for efficient use of biomass. In some areas of the UK fuels could be grown as energy
crops and in others it would arise as a by-product of agriculture, forestry and other activities.
1.9
Biomass offers important opportunities for UK agriculture and the countryside. As the
North Sea resources become exhausted, the shift from coal to oil and gas-fuelled generation
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
means that most of our fuels will come from outside the UK. This dependence on
international sources for our fuel reduces security of supply and marginalises the domestic
agricultural sector. Biomass energy provides an opportunity to develop a fuel source from
the UK’s own resources, increasing the security of its energy supply; it also offers new
opportunities for UK agriculture.
Why not biomass?
1.10 Biomass has been successfully used as a source of energy across Europe but it has not
become established in the UK; there are several reasons for this. The main problem is that
the government’s capital grants schemes for biomass initiatives have focussed on hightechnology approaches to electricity-only generation with a view to potential export
development. Demonstration schemes have not been based on established biomass
technology and they have consequently failed, with resulting loss of confidence. The
failure to recognise heat utilisation as an important way of delivering high-efficiency energy
means that opportunities have been lost. Climate change policy, not speculative export
possibilities, should be the primary driver for developing the biomass sector in the UK.
1.11 Additionally, the complexity of grant schemes has made it difficult to make headway into
developing this sector. In this study we identified 14 different grant schemes, but found no
national co-ordination. Similarly there is no national facility for the sharing of information
and experiences on biomass. At present it is too difficult for the biomass sector to grow and
government policies that are meant to make this process easier fail to do so.
1.12 These problems however are institutional rather than technical. There is no fundamental
reason why the UK biomass industry should not follow the route that has proved to be
successful in countries such as Sweden, Denmark, Austria and New Zealand. However,
growth of energy crops requires water and land and can have implications for biodiversity
and landscapes.
1.13 In this report we address these issues and discuss how they are likely to affect the take-up of
energy crop production in the UK. Any extensive use of biomass could also have significant
transport implications, and planning must allow for and minimise the associated costs and
impacts.
1.14 Combustion of biomass generates gaseous emissions and considerable quantities of ash,
some components of which (such as dioxins and heavy metals) are potentially harmful.
This report discusses these emissions and makes recommendations for the reduction of
emissions and the handling of solid wastes.
Strategy
Targets
1.15 This study was carried out following the publication of the Energy White Paper, which
accepted a number of the recommendations in our Twenty-second Report. Here we expand
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upon those recommendations and offer policy-based guidance on how to achieve them. In
particular we recommended that by 2050 up to 16 Gigawatts (about 12%) of the nation’s
energy should come from biomass (Table 1.1). This would be a clear but not dominant role
for biomass within a larger, diversified energy portfolio. Our Twenty-second Report
illustrated four possible scenarios for the future of UK energy generation, all of which
required some degree of biomass generation to meet the 60% CO2 reduction target.
Table 1.1 summarises the contributions required from biomass as set out in the four
scenarios in the Twenty-second Report.
Table 1.1 - Biomass targets from the Twenty-second report
Scenario
Biomass
GW
Total UK
GW
Biomass as % of total
GW
1
16
205
8
2
16
132
12
3
7.5
132
6
4
3
109
3
Environmental, social and economic implications
1.16 This report describes the agronomic, technological and infrastructure developments that
would be needed to deliver sufficient energy from biomass. In doing so, it discusses the
environmental, social and economic implications of each component.
Environmental
1.17 Setting aside the savings in CO2 emissions, which are common to all renewable energy
sources, the production and use of woody biomass as an energy source will have both
positive and negative effects on the environment. While these may be difficult to quantify,
we have seen evidence that the net impact will be positive. Experiences in countries such as
Austria and Sweden where use of biomass is well established are particularly encouraging.
Given the limited experience in the UK, it is important that care is taken to learn from
experience elsewhere to minimise adverse effects. Environmental impact assessments
should be carried out and the evidence reviewed at each stage of the development of a
biomass energy sector.
Social
1.18 Experience in Austria and Sweden has shown that if biomass energy is introduced
sensitively and transparently, society welcomes it. Local concern may well arise if people
see evidence of large-scale landscape changes as energy crops are introduced, or are not
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ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
satisfied that the local impacts of energy generating plants have been properly addressed.
However, guidance and standards are available to address these concerns, and it is
important that these are carefully applied.
Economic
1.19 We have also considered the cost of biomass energy. The cost of the fuel is comparable to
that of fossil fuels (particularly when the external costs of CO2 emissions are taken into
account), but the capital investment required is generally higher. In addition the grant
structure to support biomass utilisation is both complex and incomplete when compared
to the support available to other forms of renewable energy. It is not well suited to
supporting an energy source that delivers heat as well as electrical power. There is a need to
stimulate markets for heat, and there are opportunities now to do this. We have made
recommendations to address this.
A staged approach
1.20 A successful biomass energy strategy requires that by 2050 much of the fuel needed will be
grown as energy crops, and this means that potentially significant amounts of agricultural
land will need to be diverted to this use. However, in the shorter term there are existing
sources of biomass to fuel the development of the sector. We have identified four stages in
this process:
• Immediate future - energy crops utilise a relatively small proportion of
set-aside land.
• Short-term - area required for energy crops increases to an area equivalent to the
amount of set-aside land.
• Medium-term - area required for energy crops increases beyond the amount of land
that is currently set-aside.
• Long-term - area of land increases to be a significant proportion of total available
agricultural land.
The timing of these stages and the amount of land that will ultimately be needed by 2050
for growing energy crops will depend on the availability of other biomass fuels, especially
straw and forestry arisings. We consider fuel availability in chapter 2.
1.21 In chapter 3 we discuss the different approaches to converting biomass to heat and power.
We question the appropriateness of the government’s current emphasis on high-tech power
generation and we concentrate on the use of relatively simple heat or CHP plants, and on
co-firing in existing stations – these are technologies that are already available or are close to
being proven.
1.22 Chapter 4 brings our conclusions on fuel resources and conversion facilities together into
a new strategy for developing a biomass utilisation programme over the next few decades,
based around the four stages described above. We calculate the number of energy
plants that would have to be built and the amount of land that would need to be
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brought under energy crop production, and map these onto the four-stage model.
Chapter 5 is a summary of our conclusions and recommendations.
1.23 Our proposed strategy does not cover biofuels for transport or energy carriers such as
hydrogen produced from hydrocarbons. As described in the Twenty-second Report and
our analysis of the environmental impacts of air travel, transport is a prime user of
hydrocarbons. Fuels such as bioethanol from cereals and biodiesel from oil seeds may have
a role as fuels for surface transport4. Applications of woody biomass to produce transport
fuels are more speculative, they are not covered in this report as we view them as longerterm possibilities that might be appropriate if surplus biomass or land is available once the
more immediate applications have been exploited.
1.24 We also make the point that woody biomass gives a higher energy yield per hectare than
transport fuels from cereals or oil seed crops. However, in a climate of changing policies and
incentives, farmers will naturally prefer to plant annual crops rather than woody materials
which require a commitment to one crop for many years. This leads to a further theme in
our recommendations: that development of a biomass sector is dependent on stable longterm policy.
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CHAPTER 2 - BIOMASS FUELS
2.1
Biomass for fuel can be gathered or grown. Energy crops are grown using agricultural
methods; in this chapter we shall examine the main species suitable for use in the UK and
the methods of cultivation, economic value and impacts through land-take, water use and
soil contamination. Forestry and municipal tree management both lead to substantial
arisings of woody plant material that could be gathered for fuel and we shall consider the
likely arisings in the UK. The potential resources of straw from cereal and oil seed crops are
also considered.
Energy Crops
Species
2.2
Willow (Salix spp.) has already been used in commercial or near commercial operations in
the UK. Investment in developing new varieties with increased yield stability and improved
crop management has made willow increasingly competitive as an energy source
(paragraph 4.2). Willow chips are a reliable source of fuel of a consistent quality, suitable for
firing in CHP and district heating plants. Willow has been grown extensively in
Scandinavia for fuel, and in Sweden some 15,000 hectares of land are dedicated to its
production for renewable energy. Consequently, much more information about
cultivation, harvesting and yields is available for willow than for the other potential energy
crops. The grass miscanthus (Miscanthus spp.) is attracting an increasing amount of interest
but it is still largely at trial stage in the UK.
2.3
Among other potential candidate species, poplar (Populus spp.) is closest to providing an
alternative source of fuel. Poplar is being trialled in short rotation coppice (SRC)
plantations, as well as being tried in silvoarable agro-forestry where it is intercropped with
arable species. Straw has also been used as fuel and has the advantage of being a by-product
with which farmers are familiar.
Cultivation, harvesting and yield
Willow
2.4
Short rotation coppicing (SRC) is the most promising way of growing willow quickly and
easily. Breeding programmes are continuously developing new varieties that have higher
yields, better growth characteristics (straighter stems for easier harvesting for example), and
more resistance to pests and pathogens. Willow is easy and relatively inexpensive to plant
using cuttings. The stems are cut into 2 metre lengths before transportation (they can be
frozen if travelling long distances). A Swedish company5 has developed a step-planter that
cuts the stems into 15cm sections and deposits them in the soil. They are then pushed
further into the soil with a roller and left to take root.
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2.5
The first year of growth is cut back to encourage rapid, thick growth in the second to fourth
years. The willow is ready for harvesting and chipping after three years of regrowth. The
stems are cut above ground level and the stumps are left to reshoot. An average willow
coppice can be harvested over 15-20 years and the land can readily be returned to
conventional crop use in 1-2 years by ploughing in the roots and treating the soil and weeds
with herbicide.
2.6
Willow is capable of benefiting areas with loose topsoil because its roots grow into a matlike mass immediately below the surface of the soil, which helps to retain the topsoil. The
leafy canopy prevents saturation of the land during periods of heavy rainfall, reduces soil
erosion from run-off and prevents nutrients from entering streams.
2.7
Levels of pest or pathogen damage that are considered unacceptable in food crops can be
tolerated in plants that are destined to be burned. Consequently, established SRC can be
managed with few pesticide applications without incurring significant economic penalties.
Integrated Pest Management (IPM) has been addressed mainly for willow, but a number of
the recommendations could be extended to poplar. The resistance of willow genotypes to
infestation by various pests and pathogens is well understood, as are site-dependent factors
such as plants present in adjacent areas that might act as hosts to divert fungal diseases. IPM
for willow SRC recommends the planting of up to five varieties of different ages in a
plantation to enhance biodiversity. It also recommends strategic planting to concentrate
pests and pathogens in smaller areas of coppice, reducing the scale of chemical application
needed to control the pests6. Rabbits are a pest that cannot be controlled through the use of
IPM, they can pose a significant threat to willow shoots and rabbit-proof fencing is costly,
especially on irregularly shaped plots of set-aside land with high boundary to area ratios.
2.8
The emphasis, when planning SRC plantations, should be on utilising local knowledge and
planting varieties that have been tested previously on a similar site. Tailoring the plantation
to the local environment is essential. Attention to detail at the planning phase can result in
well-designed, healthy coppices with high yields, low disease and pest susceptibility and
improved biodiversity.
2.9
Conventional willow harvesting machinery cuts and chips the stems simultaneously. By
planting the willow in rows, high chipping rates can be achieved. It is important to harvest
willow in winter as it results in better wood with lower water content and allows nutrient
cycling from fallen leaves. The harvesting equipment that has been used so far is based on
that used in Sweden. There, willow is harvested in winter and the frozen ground makes it
possible for heavy machinery to move over the land without causing excessive soil damage.
In the UK the land does not freeze to the same degree as in Sweden and so this type of heavy
equipment is not suitable. A UK willow growers’ group has gone some way towards solving
this problem by using an imported sugar cane harvester7. There is no need for frozen soil
during harvesting as the mat-like roots of the willow plants adequately support the lighter
machinery.
2.10 The UK transportation infrastructure cannot yet match the rate of willow chip production, so
chips would have to be stored at the side of fields and reloaded onto trucks. The cost of
unloading and reloading chips for later transportation can be restrictively high both
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economically and energetically, and storage times and methods need to be controlled to avoid
the development of fungi leading to biodegradation, and the build up of excessive moisture.
2.11 The cane harvester used in the plantations established around the Arable Biomass
Renewable Energy (ARBRE) plant (paragraph 3.35) harvests the wood in rod form, which is
easier to transport and store and has a higher bulk density with lower moisture content.
Storing the materials in rod form also reduces the loss of material and calorific value due to
Coppiced poplar wood chips in farmer’s hands
decomposition during long-term storage8. The rods are then chipped before use, or, if
destined for use in a co-firing plant (paragraph 3.42), can be milled directly into wood dust.
2.12 UK farmers and test centres have reported varying yields for willow SRC. This variation is
likely to be the result of the variable quality of the plants, suitability of the land and more or
less effective management. Yield has also been found to depend on planting density and
frequency of harvesting9. Farmers currently see willow as a marginal crop and will make use
of subsidies by planting on set-aside land. The land chosen for set-aside is often the lowest
quality land and this could also result in reduced yields. Weeding and fertilising are
important in the first year of growth; if it is not carried out effectively then yield may drop.
Fertilising can be important throughout the growth cycle, though the amount required for
willow SRC is significantly less than for arable crops.
2.13 Climatic factors also have an impact on yield. Willow requires substantial quantities of
water and suffers reduced growth in dry conditions or dry years. Wetter regions of the UK
might be expected to be better suited to growing willow than others, though farmers have
had successful willow crops in drier areas of the UK so it seems that other factors may also
be important10. The requirements for water should be considered as part of the overall water
demand when crops are to be grown to provide energy for new building developments.
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2.14 Over the three years between harvests, the yield for willow should be ~ 20-25odt (oven dried
tonnes) per hectare (but it can be higher if grown under optimum conditions with additional
fertiliser and water). This can deliver an income of > £100 per hectare per year (ha/y) in
addition to grants and subsidies. Under the current arrangements for grants and subsidies, the
growing of energy crops is only considered to be viable at yields of 10 odt/ha/y or more11.
Yields of willow at this level are achievable through careful agronomy and by building on
experience. Willow is less economically viable as a fuel for electrical generation only, and in
chapter 3 (paragraphs 3.4 to 3.33) we have explored ways of adding value to the crop by
exploiting the potential for using it in CHP and heat-only generation plants.
Poplar and other tree species
2.15 Poplar has been trialled on a much more limited basis in the UK and results have varied
dramatically from site to site. Planting of poplar is more difficult than with other energy
crops because it is not easily propagated from cuttings. Good apical buds are needed for
effective planting and growth. Planting machinery has not yet been developed and current
practice is to use a cabbage planter; success with this machinery is limited and there is real
scope for technological developments to make the process much easier and more effective.
Land used for poplar is more difficult to return to normal agricultural use than that used for
willow, as the deep woody roots are difficult to remove.
2.16 Willow harvesting methods are also likely to be relevant to poplar although harvesting may
be needed more frequently due to the fast growing stems that thicken quickly.
2.17 Poplar trials in the UK have revealed that the yields are very site specific. In some cases
poplar yield has outperformed willow by up to 66% but in others poplar yield has been as
low as 30% of willow production12. The wide variation in yield, dependent on a number of
site-specific factors, could prove an obstacle to wide scale adoption of poplar as an energy
crop in the UK but does not rule out its use in those areas that are suited to its production.
2.18 Increasing the variety of energy crop options available to farmers enables planting to be
determined by local environmental factors, which increases farmer confidence. This also
enhances security of supply for generators, as farmers will be able to plant crops that are
more likely to thrive in their locality thus making harvests more reliable than if only a single
energy crop option were available. It is our opinion that the influence of site suitability on
yield means that farmers should be allowed as much flexibility as possible when moving
into biomass fuel production. Planting should be guided as much as possible by local
knowledge and farmers’ experience of the type of crops that they can grow on their land,
not by planting grants for specific crops. We recommend that producer group grants be
extended to include producers of energy crops other than willow. We also recommend
that the Scottish Forestry Grant Scheme be similarly extended to cover all possible
sources of biomass.
2.19 Short rotation forestry (SRF) is another option for the cultivation of a number of tree
species for energy. In SRF, trees are grown closely (as single stems) and harvested after 5-15
years. Of the many coniferous and broad-leafed species that have been trialled, ash
(Fraxinus spp.) may be the most suitable, but it requires good soil that is not acidic. On
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poorer, wetter soils, alder (Alnus spp.) has potential. In the short term SRF is not seen as a
major source of biomass for fuel, but this could change in the future.
Miscanthus
2.20 Like wheat, miscanthus (also known as elephant grass), is a member of the grass family
(Gramineae) and is grown using conventional agricultural methods and harvested annually.
It is gaining favour with farmers as it is planted, harvested and stored using existing farm
equipment and methods. It is cut and baled with a straw baler and stored in barns. It thus
requires less capital investment than willow. Farmers also have more confidence in using
current farming practices. The main disadvantage of miscanthus is that it can be difficult to
rehabilitate the land for other uses due to its deep root structure.
2.21 Miscanthus is a genus of about 20 species native to tropical Asia and Africa and like most
tropical grasses (such as maize, but with the notable exception of rice), it carries out a
modified form of photosynthesis, known as C4 (Box 2A). Most C4 grasses are cold sensitive
and do not grow well in cool regions. Miscanthus x giganteus, the cross most commonly used
for biomass production, is fairly cold tolerant and can grow (rather than just survive) at
temperatures that would not suit some arable C4 crops such as maize. Unlike maize,
Box 2A C4 photosynthesis
The key reactions of photosynthesis are the same in all plants. Light energy is converted
into chemical energy, with the production of oxygen as a waste product. The energy is used
when carbon dioxide (1 carbon atom per molecule) is added to the 5-carbon atom sugar
ribulose bisphosphate producing, after several stages, two molecules of the 3-carbon atom
sugar, triose phosphate. This is the C3 pathway, and is the starting point for synthesis of
almost everything else in the plant: sucrose, cellulose, amino acids etc.
The enzyme that carries out the reaction to produce triose phosphate also catalyses a
reverse reaction, a process known as photorespiration, in which oxygen is used and carbon
dioxide generated. This is a waste of much of the light energy that could have been used to
produce sugars etc. However, photorespiration can be suppressed by increasing the
concentration of carbon dioxide at the site where it occurs.
C4 plants can change their internal concentrations of carbon dioxide by temporary
storage of carbon dioxide in C4 acids, such as oxaloacetic acid, formed from C3 acids in
leaf mesophyll cells. From there acids are transported to bundle sheath cells (located
around the leaf veins) where carbon dioxide is released and the donor acid returned to the
mesophyll cells. In the bundle sheath cells carbon dioxide is at a higher concentration
than in the mesophyll cells and thus photosynthesis can occur without photorespiration.
C4 plants are more efficient than C3, particularly at high temperatures, and many are also
thought to control their water use more effectively. C3 plants typically have transpiration
ratios (g water lost per g carbon dioxide fixed) in the range 490-950 compared to 250-350
1
-2
-1
for C4 . Maximum growth rates (g m day ) are correspondingly higher: 34-39 for C3
compared with 50-54 for C4.
1
(Hamlyn G Jones (1993). Plants and microclimate CUP).
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
13
miscanthus maintains high levels of key C4 enzymes that function at low temperatures to
maintain high rates of photosynthesis13, although leaves may expand more slowly at low
temperatures14. Successful growth of miscanthus has been reported at an altitude of 300m
above sea level on the Yorkshire Wolds. As with several C4 grasses such as genotypes of
sugar cane, there is evidence that endophytic nitrogen fixing bacteria can occur in
miscanthus15. This could reduce the need for nitrate fertiliser, but is likely to be very
genotype-specific. There is also evidence that miscanthus may have a positive effect on
nutrient cycling and soil organic matter content (carbon and nitrogen)16. Miscanthus is
economical in its use of nutrients and has a good internal recycling system, where much of
the N, P and K (nitrogen, phosphorus and potassium) is translocated from leaves and stems
and stored in the unharvested rhizome fraction. Defra cites an ash content of 2.7% (of dry
mass), which is below average for this type of plant (paragraph 2.24).
2.22 Miscanthus is widely grown as an ornamental plant, because of its attractive inflorescences.
Genotypes developed for biomass are selected for delayed flowering and for infertile
hybrids to avoid it becoming a weed17, (miscanthus is propagated by rhizomes or by
micropropagation, so seeds are not needed to produce material for commercial use).
Although relatively efficient in its use of water, miscanthus yields may still be reduced by
drought: genotypes with tight control of transpiration have been identified for use in
breeding programmes18.
2.23 There are fewer sites planted with miscanthus for energy production in the UK than
with SRC so information is more limited. Of the seven sites for which results are
available19, two failed to achieve regular yields of 15 odt/ha/y, and one of these failed to
achieve the accepted profitability threshold of 12 odt/ha/y. Four of the remaining five
sites achieved yields in excess of 20 odt/ha/y in one or two years. However, reliable
planting and development of miscanthus rhizomes remains an issue given the limited
experience to date.
Other grasses
2.24 Most work on evaluating grasses other than miscanthus has been carried out on canary reed
grass (Phalaris arundinacea), a C3 species native to Europe. Canary reed grass is a rhizomatous
perennial that is grown from seed, reducing establishment costs, and can be harvested 2-4 times
a year. It produces harvestable material earlier than miscanthus and can be processed with the
same machinery as wheat straw. It can be grown in cold areas such as Finland20. The first harvest
in the spring is of the previous year’s growth, before new tillers are produced; this has a low
water content (10-15% dry weight). It does not need high levels of nitrogen, indeed it can be
used to take up nitrogen from polluted waters and it may have an additional use in cleaning up
heavy metals from municipal sewage21. On the other hand it can become very invasive of
wetlands and is in fact banned from some areas in North America. Canary reed grass was one
of four perennial rhizomatous grasses selected for evaluation for energy crops in Europe and
USA. The others were miscanthus, giant reed C3 (Arundo donax) and switch grass C4 (Panicum
virgatum). Both giant reed and canary reed grass inhabit wetlands, and so would not be a
suitable alternative to arable crops on high grades of agricultural land. The ash content of C4
grasses is typically around 8%, about double that of C3 grasses. This ash is primarily fine silica,
which adds to the fly ash produced when the grass is burned22.
14
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Straw
2.25 Cereal crops consist of roughly equal parts grain and straw, oil seed crops such as rape
produce roughly 1.5 tonnes of straw per tonne of seed23. These ratios imply that the total
amount of straw produced in the UK was almost 24 million tonnes in 2002. This straw may
be used for animal feed or bedding, and there are limited export markets, for example to
Holland for use in tulip cultivation.
2.26 Many farmers prefer to plough straw back into the field to improve the organic content and
texture of the soil. This use for straw has only come about in response to a ban on burning
straw, which had been the practice for many years, and there are divergent views on its
benefits, especially in terms of nutrient content (paragraph 2.27). The volume of straw
available in the UK is considerable and it is likely that a significant surplus would be
available for use as fuel from those farmers that choose to market it for energy generation.
Environmental implications
Energy use during production
Table 2.1 Energy use and greenhouse emissions from fuel
production24
Resource
Energy use (Mj/odt)
CO2 equivalent emissions
(kg/odt)
Forestry residues
572
33
Straw
1253 (a)
171 (a)
(baled)
-31 (b)
-4 (b)
Short rotation coppice
756
35
338
40
(chips)
(chips)
Miscanthus
(baled)
2.27 Table 2.1 shows the energy use and CO2 equivalent emissions from fuel production,
including direct inputs, indirect inputs and resource-related inputs. These have been
converted from values per wet tonne to values per oven-dried tonne (odt). Two values for
energy use and emissions for straw have been given as a result of the possibility of varying
fertiliser input assumptions (paragraph 2.26), which have a large influence on the estimates.
In case (a), fertiliser inputs are used to replace nutrients lost when straw is removed from the
field instead of being ploughed in. As a result, indirect and resource energy use and
emissions are large, and are significantly greater than for the other fuels. However, if it is
assumed that replacement fertiliser is not needed (case (b)), the energy and emissions are
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
15
negative compared with ploughing in. But even in the worst case, the CO2 savings from
using biomass rather than fossil fuel (about 1,000kg CO2/odt equivalent for gas) massively
outweigh these emissions.
Water requirements
2.28 The high water requirement of willow can constrain its use to areas where sufficient
irrigation water is available at reasonable cost and without unacceptable environmental
damage (paragraph 2.13). However, municipal sewage or sewage sludge can be used to
irrigate willow, and will provide both additional nutrients and water25. Water companies
have already shown an interest in this disposal routei, which could provide an additional
revenue stream for farmers as well as reducing their fertiliser input costs.
Willow and heavy metals
2.29 The high heavy metal content of sewage used as fertiliser can raise concerns over soil
content. Willow, however, will take up heavy metals, particularly cadmium, and
concentrate them in the wood. Willow plantations can therefore actively reduce levels of
metals in contaminated soils26 (Figure 3-V) and can be used for the bioremediation of
contaminated land. Subsequent care in managing the ash from energy production is
important to prevent unacceptable build up of heavy metals in the soil. We address this in
chapter 3 (paragraphs 3.53 - 3.56).
Landscape
2.30 The English landscape is not constant; it has been in a state of change for centuries as
humans have changed the use to which they put the land27. Change need not be
undesirable, but substituting one landscape for another will be of significance to those who
value the landscape and decisions on land use should be made cautiously. A change of land
use from arable cropping to willow coppicing or miscanthus cultivation over a large area
would have a significant impact on the landscape - a mature willow crop can grow to four
metres in height before harvest and miscanthus can reach similar heights.
2.31 Willow plantations need not be visually intrusive if planting is planned sensitively. The
Forestry Commission has produced a guideline note28 on planning plantations of SRC
(willow in particular) and minimising the impact on the landscape. The guidelines
indicate that irregular-shaped plantations on low-lying land that are sympathetically
shaped and managed are the best option for such a visually intrusive crop. The Forestry
Commission emphasises that planting coppices of various ages near to existing tall plants
(woodlands for example) reduces dramatic landscape changes after harvest; it also
suggests incorporating public rights of way and planting areas of shrubs around these to
improve diversity and visual interest. It is important to avoid planting large, geometric
shaped coppices on high ground that can block local scenic views, especially in
recreational areas.
i
16
Yorkshire Water’s initial interest in the ARBRE project was in using the SRC as a sewage disposal route.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
2.32 Straw is a by-product of an existing crop so few, if any, landscape changes would be likely to
result from its adoption as an energy fuel. Likewise forests are an existing landscape feature
and their use as a source of fuel will have little or no landscape impact but improvements in
forest management could increase their accessibility for public recreation.
Biodiversity
2.33 Short Rotation Coppice provides cover that is not supplied by arable crops or grassland
and weeds are better tolerated. This can provide an environment attractive to small
mammals, invertebrates and insects29, which in turn attract many species of bird. Ground
nesting birds are attracted to SRC especially after harvest or first year cutback. Sensitive
planting of SRC can improve game bird prospects, and pheasants in particular value the
shelter that a well-established crop can offer. An average SRC plantation can exist for 15 or
20 years, providing a more stable and mature environment for wildlife than annual crops.
This is particularly true for winter-sown cereals which, as currently managed, do not
support a high level of biodiversity.
2.34 The fauna attracted to coppices are similar to those found in woodland. Planting SRC
adjacent to woodland not only reduces the visual impact of the plantations but also
provides ecological corridors for the movement of wildlife. The cover provided by a
coppice offers opportunities for bird watchers and animal enthusiasts as it also attracts
larger mammals such as deer. Unfenced willow and miscanthus plantations may, however,
shelter rabbits that may graze neighbouring crops.
2.35 Sensitive planning is central to the issue of improved biodiversity. Replacing wetlands or
other natural habitats is likely to result in a net reduction in biodiversity. The water demand
of willow means that the crop can have an impact on an area beyond the plantation
boundaries especially if it is sited close to wetlands or small local streams. Fish and other
waterborne creatures can be negatively affected by a reduction in the water table due to the
high water demand of coppicing in nearby areas. This is addressed in the EC
Environmental Impact Assessment Directive that requires an assessment to be carried out
before uncultivated or semi-natural areas are converted into intense agriculture if this is
likely to cause significant environmental effects30.
2.36 Poplar appears less able to enhance biodiversity than willow, particularly in respect to
insects31. However, poplar coppices can tolerate higher weed populations and weed seeds
are an important bird food. There may also be benefits for biodiversity of invertebrates
such as spiders, beetles and slugs32. Poplar plantations also tend to sustain more stable and
diverse plant communities, with fewer annuals and invasive perennials33.
2.37 As yet there are few data available on the biodiversity impacts of other energy crops such as
miscanthus, though similarly a miscanthus plantation might provide better cover, higher
weed-growth and lower pesticide usage than arable crops.
2.38 We recommend that the biodiversity benefits of energy crops be reflected in the
Energy Crops Scheme, with payments matching those available with respect to
biodiversity enhancement through the Countryside Stewardship Scheme. The Energy
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17
Crops Scheme goes some way towards this by allowing open spaces within plantations to be
included in the area that is counted in the awarding of grants, but payments based on set
criteria for sensitive planting of a variety of species and ages and incorporating public rights
of way and wildlife corridors would provide better incentives for farmers embarking on
energy crop production. The possibilities for integrating energy, farming diversity,
Box 2B Land classification in England and Wales
Agricultural land is divided into classifications by the physical limitations of the land for
agricultural use, the determining factors being climate, site and soil and how these affect the
versatility of the land and the reliability of crop yields1. England and Wales have five
classifications (or grades) and grade 3 is divided into subgroups a and b2, the Scottish executive
uses seven grades of land classification with up to three sub-categories in each3, The first five
follow roughly the descriptions and proportions set out below for England and Wales4.
Grade 1 - excellent quality agricultural land
3% of agricultural land
Land that produces consistently high yields from a wide range of crops such as fruit, salad
crops and winter vegetables.
Grade 2 - very good quality agricultural land
16% of agricultural land
Yields may have some variability but are generally high, some factors may affect yield,
cultivation or harvesting.
Grade 3 - good to moderate quality land
55% of agricultural land
Limitations of the land will restrict the choice of crops, timing and type of cultivation,
harvesting. Yields are generally lower and fairly variable.
Grade 4 - poor quality agricultural land
16% of agricultural land
Severe growing limitations restrict the use of this land to grass and occasional arable crops.
Grade 5 - very poor quality land
10% of agricultural land
Land that is generally suitable only for rough grazing or permanent pasture.
Defra (2003). Agricultural Land Classification. Protecting ‘the best and most versatile agricultural land’
MAFF(1988). Agricultural land classification of England and Wales
3
Personal Communiction, J Hooker, April 2003.
4
Defra. England ALC stats
1
2
18
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
biodiversity and recreation targets should be recognised and encouraged through
additional payments to farmers that meet these standards.
Potential production
2.39 England has about 2.5 million hectares (Mha) of grades 1 and 2 agricultural land, 6 Mha
of grade 3 land and 3 Mha of grades 4 and 5 land. Food production is likely to continue
on the best grade 1, 2 and 3 land but a significant amount of land in grades 3, 4, and 5 will
be available and suitable for energy crops. Environmental impact assessments may rule
out some areas of set-aside and grade 5 land for energy crop production on
environmental grounds, or it may just be unsuitable (steep slopes or very poor quality soil
for example). Therefore it is more likely that grades 3 and 4 land will be used for willow
production. Energy crop production could be started as a use for set-aside land but it is
likely that eventually other arable land would need to be switched to energy crop
production.
2.40 There are currently 1,795 hectares of land under cultivation of commercial willow SRC and
miscanthus in the UK34; at least 1,500 hectares of this is willow35. The land dedicated to
energy crops totals less than 0.01% of the total arable land in the UK36. The Defra NonFood Crops Strategy states that domestically grown crops should meet a significant part of
the demand for energy and raw materials in the UK37. The National Farmers’ Union
suggests that up to 20% of crops grown in the UK could be made available for non-food
uses (i.e. for fuels or industrial materials), by 202038; hence, there is scope for a significant
expansion of energy crop production in the UK. Planning crops in order to achieve the
maximum environmental benefits and yields in areas close to demand is the challenge to be
met by the farmers and energy generating companies
2.41 The implications for UK land availability can be considered in four stages:
• Immediate future - energy crops utilise a relatively small proportion of
set-aside land.
2.42 For the immediate future, the indications from power plants in the planning stages are that
farmers can be attracted to allocate sufficient land to growing energy crops by the existing
set-aside and planting grants39,40 with a proportion of growers not using
set-aside land.
• Short-term - area required for energy crops increases up to the amount of
set-aside land.
2.43 The average set-aside land over the four years from 1999-2002 was 640,000 ha. It is unlikely
that all of this will be suitable or available for energy crops, for a variety of reasons including
farmers’ preferences for other industrial crops, water availability, commercial return and
land productivity. Therefore, it is likely that a change in grant regime will be required to
ensure that land equal in area to the total area of land that would otherwise be set-aside is
used for non-food crops, with an appropriate proportion being energy crops. This is likely
to result in much set-aside land being returned to its former uses, with some land remaining
fallow, whilst other land is converted from other crop production to energy and industrial
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
19
crops. The new CAP single payment scheme is understood to make energy crops more
commercially viable41 for farmers but additional drivers will be needed from government to
encourage wider-scale take-up of energy crop production.
• Medium-term - area required for energy crops increases beyond the amount of land
that is currently set-aside.
2.44 As a viable fraction of set-aside is used for energy crops, growth in energy crops will move
onto other grades of land. The issues then become effective agricultural and forestry policy
and the relative profitability of different land uses. Agricultural policy issues that arise
include import and export balances of food crops and the effect of a possible move to less
intensive and lower output farming methods. Within the UK there will be many
geographical variations, for example the availability of water for SRC, so the cover of these
new crops will not be evenly spread throughout the country. Further evidence42 suggests
that, in the short to medium term, Scotland will have sufficient biomass from forestry
arisings and co-products to meet its needs and will not need to grow dedicated energy crops.
• Long-term - area of land increases to be a significant proportion of total available
agricultural land.
2.45 In the long-term, in addition to the economic and policy issues above, the environmental
impacts would become more significant. Siting of energy crop production would be
constrained by both proximity to installations using the biomass and the suitability of the
land. To achieve the levels of biomass energy production suggested by some sources43 would
require at least 20% of the total available arable land area, and would be likely to result in
many large areas having much more than 20% of land area dedicated to energy crops.
Conclusions on energy crops
2.46 This land will not come into energy-crop cultivation unless it provides an adequate return
for farmers. The Energy Crops Scheme (Appendix A, paragraph A.6) intends to encourage
farmers and end-users to work together and to ensure that supply and demand are both
satisfied. It takes account of factors such as environmental and landscape issues as well as
energy requirements. The scheme already recognises the biodiversity value of SRC to some
extent. We recommend that the Energy Crops Scheme be enhanced to make energy
crops more viable for farmers, and be tied to specific planting standards to protect
landscape and other environmental features. This would help to reassure environmental
groups and the public that SRC plantations cannot be established indiscriminately at the
expense of the local environment. It would also provide a higher income stream for farmers.
2.47 Successful cultivation of energy crops would have two positive outcomes. A fuel would be
produced for use in biomass energy generators in a way that is not a by-product of, and
therefore limited by, a different type of operation such as forestry or municipal tree surgery;
and a valuable cash crop with additional financial support would become available for
farmers. Set against this are limitations imposed by processing and transporting the fuel.
However, without guaranteed markets farmers are unable to receive Defra establishment
grants for energy crops and they are understandably hesitant to dedicate large areas of their
land to a crop that is relatively new to the UK.
20
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
2.48 While in general willow and poplar perform better in wetter areas and miscanthus yields
are likely to be higher in warmer areas less prone to frost, energy crops can be grown in
much of the UK. A detailed investigation needs to be carried out into the suitability of
areas of the UK for biomass energy. We recommend that extensive detailed analysis of
the suitability of land for energy crop production and a comparison of this to
possible markets for the energy be undertaken on a regional basis. This should be
carried out with central government support and guidance and should aim to
incorporate environmental, agricultural and fuel poverty issues as well as economic
considerations.
Forestry Products
Trends in availability
2.49 Historically, woodcutting has fuelled domestic or industrial stoves and has provided the
raw material for products such as charcoal and other processed or semi-processed wood
fuels. In the developed world the use of wood in this way has been largely abandoned in
favour of other forms of energy, and forestry is now primarily directed towards the
production of timber and paper pulp. The demand for paper pulp in the UK is decreasing
as recycling increases, and the demand for construction timber from UK forests has also
decreased; consequently the availability of wood for fuel has increased. Added to this, large
amounts of Britain’s forests were planted in the 1960s and 1970s and will soon be reaching
maturity without a clear market for the wood.
2.50 Figure 2-I illustrates the anticipated wood production from forests in Britain from 1994
to 202144. Supply is predicted to increase over the next couple of decades, peaking at
about 10 million tonnes per year above current demand by 2020. Not all of these forests
will necessarily be replanted so wood production could decline after 2020. This,
however, will be offset to some extent by bringing more forests under active
management. Demand for UK-grown timber might increase over the same period
because of the large-scale house building currently foreseen in government strategies for
housing and planning45. Competition from imported timber however will mean that UK
materials will not be used to meet all of the domestic demand and some surplus wood
will still be available as fuel.
2.51 We expect that much of the extra 10 million tonnes per year of production by 2020 will
be available as biomass fuel for energy, and that the supply will then fall to a level
dependent on the competitivity of the UK industry. Long-term supply cannot be predicted
but it is likely to be significantly higher than the current availability of 1.3 million tonnes
per year.
2.52 A market for bioenergy in Britain would provide an opportunity for Britain’s forest
industry to receive income from its residues; giving the forest industry a market for its byproducts and increasing its competitivity and helping it to resist decline. Under such
conditions the economic strength of the industry may be sufficient to utilise the increased
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
21
potential harvests projected in Figure 2-I. As the primary products comprise only half of
the trees cut, a growing forestry industry would provide a growing supply of biomass
residues for energy purposes at a low cost. Whether demand for UK timber increases or
decreases over the coming decades, biomass energy provides an additional market that
could complement other wood-based industries to develop the forestry sector.
Figure 2-I Supply and demand of GB wood
20000
18000
Thousand m 3
16000
14000
12000
10000
8000
6000
4000
2000
2020
2018
2016
2014
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
0
Year
Total GB wood availability
Demand for GB wood
2.53 Forestry materials available for biomass fuel arise as a consequence of other forestry
activities, so that the marginal energy costs of and emissions from its production are
minimal. Should the production of fuel become again a major objective of forestry, it
would be necessary to investigate the costs and environmental impacts of keeping land in
forestry as opposed to releasing it to other uses, as well as the energy requirement of
harvesting and transporting the materials. The opportunity to sell forest arisings as an
energy fuel could make forest management more economically viable. This is an
opportunity to use an existing resource and improve the management of the UK’s forests
and woodland as a result. We recognise that it is important, however, to monitor the impact
of removing arisings from the forest. In some areas the physical removal of arisings could
cause unacceptable effects on soil structure (leading to erosion) and nutrient retention
(leading to possible acidification and eutrophication of waters). Sufficient materials must
be left on the forest floor to prevent this from occurring.
2.54 Management of planted forests to produce fuel for energy could offer a valuable opportunity
to rethink the UK’s forests and to replant with a diversity of indigenous species to replace the
single species planting prevalent in many of the UK’s forests. This recommendation was
made in the Commission’s Twenty-third Report46. We recommend that the Woodland
Grant Scheme for England and Wales take a similar approach to the Scottish Forestry
Grant Scheme, which recognises this potential and structures the grant payments to
reward planting of selected broadleaved trees in new and improved woodland areas47.
22
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Accessibility
2.55 If forests are located in remote areas, there may not be access for harvesting machinery or
transportation and it may be uneconomic or unattractive to invest in building roads.
Building access roads in unspoilt areas is usually undesirable but this would only apply to a
small proportion of the UK’s forests and should not be considered a general obstacle to the
use of forestry materials for fuel. The long lead-time, uncertainty of supply (a glut followed
by scarcity of supply in some areas following the 1987 storms for example), and a lack of
expertise in harvesting methods all detract from the value of forest materials as a long-term
source of fuel compared to energy crops, for example, that are more controllable. However,
in those areas close to forests, the benefits of using an existing local resource for energy
production are clear.
2.56 Forestry products are not suitable for all modes of biomass conversion. The dispersed nature
of the supplies makes it unlikely that they will be used for large-scale energy production. The
fuel is often insufficiently homogenous for small-scale plants without considerable preprocessing to increase the density and uniformity and reduce moisture content. A typical
product is compressed sawdust in the form of pellets but the energy and economic
requirements of such a process impacts on the suitability of the fuel and must be handled
accordingly – this is discussed below (Box 2C). The Finnish Alholmens Kraft is a very large
cogeneration plant that is located at the site of a pulp plant so that both industrial residues
and forestry co-products from the primary product collection can be used as fuel48. This
could serve as a model for UK applications of biomass energy.
Impact on other industries
2.57 There are several industries that rely on forestry materials, particularly wood and sawdust,
as an input material. In the absence of other factors a sharp rise in demand for biomass
could potentially increase prices and so decrease the competitiveness of such industries; if
so, this would need to be reflected in any economic analysis of biomass fuel. However,
supply of forestry materials is increasing much faster than demand (paragraph 2.50) and a
significant increase in prices is unlikely to materialise49. In addition, these wood-based
industries produce by-products that themselves have potential as fuel, and some farms and
manufacturers already use their own by-products to fuel small-scale CHP units (Box 2C).
Forests as Carbon Sinks
2.58 The Kyoto Protocol acknowledges the value of forests as carbon sinks and promotes
afforestation as a way of achieving national targets for CO2 reduction set under Kyoto.
Only forests that are planted post-1990 are eligible for accounting under this system.
Carbon sequestration through afforestation accounted for around 0.4 million tonnes of
carbon (MtC) in the UK in 200150. Use of surplus forest materials to displace fossil fuels as
an energy source would have a much more significant impact than afforestation on
reducing CO2 emissions towards the Kyoto targets.
Availability and costs
2.59 The dispersed nature of forest materials means that they are better suited to small scale
CHP or district heating applications. The rural location of most forests makes them ideally
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23
placed primarily (but not exclusively) to serve rural communities. There is an opportunity
to link biomass energy policy with rural regeneration and fuel poverty strategies. The
economic returns on rural schemes may be lower than in urban areas due to the lower heat
demand density in rural areas51.
2.60 Encouraging co-operatives between foresters would increase their influence in the energy
sector and spread the capital costs and risks between a number of stakeholders. Energy
generators are likely to support such moves; dealing with a single co-operative rather than
a number of individual farmers or foresters reduces administration costs. We recommend
that the government investigates the possibility of extending the grants for
establishing producer groups to farmers and foresters who wish to use their
woodlands or other arisings (hedgings for example), as a source of fuel but do not wish
to plant energy crops.
2.61 The benefits associated with forests are not exclusive to rural areas. The Office of the Deputy
Prime Minister’s (ODPM) Sustainable Communities programme (paragraph 4.18)
incorporates the planting of a number of community forests for recreation. We recommend
that the infrastructure for management and distribution of forest resources should be an
integral part of the planning process; these materials should then be used in local
community heating or CHP schemes to improve the sustainability of these communities.
2.62 One of the key advantages of forestry material is that there is already a surplus of wood that
could be made readily available for use as a fuel. With a supply peak around 2020
(Figure 2-I), forestry materials can be used to initiate the biomass energy sector and support
its development over the next couple of decades. This would allow energy crops to be
planted at a gradual rate enabling the environmental impacts of the change in land-use to be
periodically monitored and reviewed. By the time forestry materials begin to decline (post
2020), sufficient energy crops should have been planted, and yields increased, to allow
them to take over the lead in energy production.
Sawmill co-products
2.63 The main demand for forestry materials currently comes from sawmills but these mills
produce by-products that could in turn be used as biomass fuel in either their raw state or
following processing. Chipboard manufacturers would be in competition with energy
companies for sawmill by-products but they also produce by-products that could be
employed for energy production. Sawdust can be compressed into wood pellets that can be
used in domestic or industrial applications. Pellets have the advantage of being dense, clean
and dust-free so they are easy to transport, store and combust in smaller-scale operations
that require a more consistent fuel.
2.64 Using biomass resources produced on-site to provide heat and power for the pelleting
procedure, as Balcas does (Box 2C), reduces the environmental impact of the process
significantly. Sawmills, chipboard manufacturers and other processors of virgin wood are
ideally placed to develop on-site biomass CHP and pelleting schemes along the Balcas
model (albeit on a smaller scale).
24
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Box 2C Pelleting sawdust
The pelleting process can be scaled according to the resource available. Balcas Ltd is a
company based in Northern Ireland that owns 4 sawmills, 2 pallet factories and an MDF
mouldings plant. They have recently been awarded a capital grant from the DTI to build a
CHP and pellet mill extension onto their sawmill in Enniskillen. Balcas will use surplus
sawdust and woodchip from the mill to fire a 15MW boiler to produce 2.7MW of
electricity and heat to dry further wood, to produce wood pellets and power and heat the
entire facility. The pelleting operation will produce 50,000 tonnes of pellets per year and
these will be sold to external customers.
This scheme will cut energy bills and fossil fuel consumption, and will dispose of the mill’s
co-products in a safe and convenient way, which will bring additional income to the
company (provided they have a market for the pellets).
Construction of the pelleting and CHP plants is due to begin in early 2004. It is worth
noting that the grant has been awarded only for the CHP facility and that there is no
specific government support for the pelleting operation under this particular initiative.
2.65 In some European countries the take-up of small-scale domestic wood-fuelled heaters
increased dramatically with the increased availability of wood pellets. Wood pellets have
been particularly successful in promoting the use of biomass for heat in Austria
(Figure 2-II). A large pellet market and distribution system has developed that enables
homeowners to install domestic pellet heaters confident in the knowledge that they will be
able to obtain a regular, reliable supply of fuel. In Salzburg, 50% of all new-build projects
now incorporate biomass heating, 70% of which use pellets as fuel52.
53
Figure 2-II Biomass heating in Austria since 1986
60,000
40,000
30,000
20,000
10,000
2002
2000
1998
1996
1994
1992
1990
1988
0
1986
Number of installations
50,000
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
25
2.66 The Forestry Commission estimates that the sawmill co-product available in Britain totals
around 859k odt/y, 20% of which is sawdust54. There are existing markets for 98% of this
resource but the Forestry Commission estimates that around half the sawdust could be
made available for fuel without serious disruption to existing industries. Any increase in
availability of sawdust for pelleting in the future would come from either an increase in
sawmill activity or a decrease in other markets for sawmill co-products.
2.67 Any significant increase in pelleting in the short term would have to come from processing
other sources of wood (willow, forestry materials etc). Wood Energy Ltd in Devon is
developing miscanthus pelleting to improve the manageability and density of the fuel and
they are currently trying to secure funding for firing trials55.
Municipal arisings
2.68 The maintenance of parks, gardens, road and rail corridors and other green spaces in towns
and cities gives rise to plant cuttings that are typically woody and suitable for use as
biomass fuel. The civic community already incurs the costs of producing and collecting
the material as part of its normal operations, and any marginal costs of delivering to an
energy plant instead of to a landfill site will be slight if not negative, particularly if gate fees
are consequently avoided. The increases in the landfill tax and the introduction of the
Landfill Directive56 are requiring councils to look for alternative disposal routes for
their biodegradable wastes.
Using woody arisings to
produce energy is an
alternative route for these
materials. Some of the
material might be suitable
for composting, digestion or
further processing into solid
fuel (sawdust pellets) and the
cost of this would depend
on the local availability of
outlets for its use in this way.
2.69 The Forestry Commission
estimates that the quantity
of park and garden waste
arising in towns and cities
could total 492k odt/y if
this resource were exploited
fully. The dispersed nature
of the resource makes this
fuel especially suited to
small-scale, district heat or
CHP production, to reduce
transport distances and
26
Forestry workers feed cut branches into shredder
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
costs. There are however few opportunities to store or process municipal materials at
source, which affects the possibility of allowing the fuel to dry to the low moisture content
required for some small-scale operations.
2.70 A project in South London, BedZED (Beddington Zero Energy Development), will use
wood from municipal tree management in a small CHP plant using gasification in a
housing development that aims to be energy-neutral (Box 2D). It was funded by capital
grants from the Combined Heat and Power Association (CHPA) and the Energy Saving
Trust (EST). The EST was established by the DTI to encourage the sustainable use of energy
and to help the government to achieve its carbon reduction targets. There has been no
direct government involvement in the scheme but Patricia Hewitt (Secretary of State for
Trade and Industry) chose BedZED as the site of the launch of the Community Energy
programme, thereby lending weight to the scheme.
Box 2D BedZED
BedZED, the Beddington Zero Energy Development, is a development of 100
properties including housing, work units, shops and green spaces. It has been designed
to have as little environmental impact as possible. Through the combination of energy
efficiency and sensitive design it is estimated that residents will see a 60% reduction in
heat demand compared to a typical suburban home.
BedZed aims to be carbon neutral through the use of renewable energy converted onsite. A combined heat and power unit no larger than a small home will meet all the
energy demand, fuelled by arboricultural arisings from Croydon Council’s park
management (which would otherwise go to landfill). The CHP unit has been sized to
supply the entire heat demand of BedZED and the average electricity demand. At times
electricity will be exported to the grid, to be retrieved during periods of peak demand
when the CHP electrical output is insufficient. The CHP plant uses a gasification
process with a reciprocating gas engine (paragraph 3.15). It is currently the subject of a
start-up programme to achieve reliable operation.
2.71 Some councils are piloting biomass CHP and district heating schemes in their public
buildings. Nottinghamshire County Council, for example, has installed biomass heating in
three of its schools, to be fuelled by forest materials from the local area. However, they
currently have to use more expensive wood pellets as it is proving problematic to establish
a reliable supply chain from local foresters in the absence of government support57. This
provides the public with examples of the application of reliable, efficient CHP and
encourages acceptance of the new technologies but the supply chain problems must be
resolved to attract further interest in biomass schemes.
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27
Classification as waste
2.72 Forestry materials, municipal arisings and straw are all secondary products; consequently
some of these materials might fall under the legal definition of waste. The classification of a
material as a waste depends on whether it has been discarded or is intended or required to
be discarded regardless of whether there is a market for it as a product58.
2.73 In broad terms, the ramifications of materials being designated as wastes impact largely on
their transportation. Waste transfer notes must accompany waste materials during transit.
As the disposal of these materials is current practice, existing transport arrangements
should already be in compliance with waste regulations where necessary.
2.74 The classification of these materials as waste need not affect their use as a fuel. Plants that
are fuelled by virgin, untreated wood are excluded from the Waste Incineration Directive59.
This means that biomass plants burning municipal arisings or forestry wastes either alone or
with energy crops or co-fired with coal should not need to be classified as waste
incinerators. However, we recommend that all potential biomass schemes confirm the
legal status of their operations on a case-by-case basis.
2.75 Separate from the legal question is the issue of public antipathy to the processing of waste
in their neighbourhood. It has been reported60 that certain biomass stations have met with
opposition when local residents have become concerned that the plant may be used as a
waste processing plant in the future, even when this was not in the project plan. It may be
easier to promote wood gasification technologies that require a homogenous fuel that is
clearly distinguishable from waste; but with the development of advanced technologies
such as pyrolysis that can accommodate very heterogeneous fuel sources, this is likely to
become an increasingly prominent issue. It is important for acceptability that biomass
plants are kept distinct and separate from waste disposal operations; this will only be
achieved if operators are scrupulous and transparent about the source of their fuel.
Conclusions
2.76 The Forestry Commission has calculated that about 3.1 million odt/y of wood-derived fuel
could currently be made available in the UK61. This includes forestry materials, sawmill coproduct, municipal arisings and energy crops (but not straw). This is equivalent to 440MW
of electricity (at a conversion rate of 20% in an electrical output only plant), which is about
half of the UK’s commitment to electricity production from biomass, even without
additional planting of energy crops. The same amount of fuel could also produce some
1400MW of heat (assuming 85% total efficiency). This assumes full and easy access to all of
the UK’s current biomass resource without competition for these materials from other
industries. If competition for this wood from other industries is taken into account, an
estimated 1.3 million odt/y could be made be available; this is a sufficient resource to
initiate a sizeable biomass for energy sector, and it is available now.
2.77 The biomass for energy chain is currently disjointed and there is insufficient
communication between the stakeholders involved. We recommend that a new
28
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
government/industry forum should be established, consisting of representatives from
all parts of the biomass for energy supply chain, including farmers, transporters,
generators, construction companies, local councils and central government policy
makers. The forum would allow its members to identify problems, share solutions and
experiences and make recommendations on improving the effectiveness of biomass
energy policy. Currently the process of establishing schemes is fragmented and relies to a
great extent on local knowledge and enthusiasm and the drive of a few local entrepreneurs.
Setting up a discussion forum would allow knowledge and experience to be shared to the
benefit of all, and produce policy recommendations to enable biomass energy to be
promoted more effectively.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
29
CHAPTER 3 - GENERATION USING BIOMASS FUELS
General Principles
3.1
Biomass can be converted into energy by simple combustion, by co-firing with other fuels
or through some intermediate process such as gasificationii. The energy produced can be
electrical power, heat or both (combined heat and power, or CHP). The advantage of
utilising heat as well as or instead of electrical power is the marked improvement of
conversion efficiency - electrical generation has a typical efficiency of around 30%, but if
heat is used efficiencies can rise to more than 85%. This chapter describes these
technologies, and considers the amount and types of generation that would be needed to
meet the renewable targets discussed in chapter 1 (paragraph 1.2).
3.2
In each type of plant, the overall reaction for a fuel of mean composition Cx Hy Oz is
Cx Hy Oz + (x+y/4-z/2)O2
x CO2 + (y/2) H2O
The total energy released by this reaction is independent of whether the fuel is burned in a
combustion plant, pyrolysed (i.e. heated to decompose the fuel) or gasified (i.e. heated in a
flow of a gas, usually air or steam). If the gas and char from pyrolysis or gasification
are then burned, the overall reaction is the same as the above; the differences in
performances between combustion and pyrolysis or gasification lie in the way in which the
heat is released and utilised.
3.3
Biomass differs from other fuels in several respects, of which two are particularly significant
for heat, CHP or power plants using biomass. The calorific value - i.e. the heat released by
burning a specified mass of fuel- is relatively low. Furthermore, the water content of the
combustion gases is relatively high, both because of the hydrogen present in the fuel (see
above) and because most biomass fuels contain some degree of moisture which evaporates
when the fuel is burnediii. To recover the energy retained in the water vapour, it is necessary
to use a condensing heat exchanger which converts the water vapour to liquid and recovers
the latent heat of evaporation; this is currently considered an undesirable degree of
complication for simple heat and simple CHP plants. However, the overall efficiency is
generally improved if the biomass is dried before firing, to reduce the water content of the
combustion gases.
ii Some types of biomass can be converted to energy through other means, such as anaerobic digestion
to produce methane or fermentation to produce ethanol. These methods are not well suited to the
lignocellulosic materials being considered here and are therefore not included in this report.
iii Two measures of calorific value are used: the Gross Calorific Value (GCV, or higher heating value),
which measures the heat released when the fuel is burnt and the water is condensed out of the
combustion gases as a liquid and the Net Calorific Value (NCV, or lower heating value), which
measures heat release on the basis that the water remains in the vapour phase. The difference between
GCV and NCV is higher for biomass than most other fuels, and is widened by increasing moisture
content.
30
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Heat generation
Description
3.4
The simplest kind of process,
Figure 3-1 ‘Heat only’ combustion plant
a plant that provides heat
output only, is shown
schematically in Figure 3-I.
To stack
The fuel is burned with air in a
combustion chamberiv. The
Gas cleaning
Fly ash
hot gases produced by
combustion pass into a heat
Cool water
exchanger, where they cool
and transfer heat to another
Heat
exchanger
fluid. In the case of a heating
Hot water
plant, such as for district
heating, this fluid is water that
is pumped through the heat
Fuel
Combustion
exchanger and circulated to
chamber
distribute the heat. The
Air
Bottom
cooled gases are then cleaned
ash
to remove particulates and
other pollutants before being
emitted to the atmosphere
through a chimney or stack. Typically up to 90% of the Net Calorific Value of the fuel can
be recovered as heat; the proportion is higher (and can exceed 100%!) if a condensing heat
exchanger is used.
3.5
Most of the non-combustible part of the fuel - primarily minerals - leaves the combustion
chamber as bottom ash. Finer particles are conveyed out of the combustor and removed in
the gas cleaning stage, along with any material injected to clean the gases, as fly ash. Bottom
ash and fly ash are commonly handled and disposed of separately.
Practical application
3.6
Heat-only applications for biomass are constrained to locations where biomass fuel is
available and a market for the heat exists. At present this makes them particularly suited,
but not limited, to rural areas without access to the gas grid. These areas otherwise have to
resort to costly and polluting oil-fired heaters, electric heating or older wood stoves which
are usually inconvenient and inefficient. The use of locally produced materials could also
help with rural regeneration through investment and employment opportunities and
provide an alternative market for sectors such as forestry (paragraph 2.59).
iv A range of possible combustion chamber configurations is available but, for the sake of simplicity,
this kind of detail will not be considered here; nor will the various detailed refinements which can be
employed to improve the efficiency of any of the general processes be discussed.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
31
3.7
Wood from forest management seems therefore to be a particularly suitable fuel for heat
producing plants. The college of West Dean in Sussex has operated a successful example
of this type of development since 1980. Thinnings and other surplus wood arising from
the management of woodland on the college estate fuel the heating system for the
college. This provides both an economic incentive to maintain the woodland and a
substantial cost saving on the college’s fuel bills. Further details of this scheme are in
Appendix B.
Chipper and storage shed
32
3.8
Another example of a small-scale wood-fuelled heat facility is a community housing
association in Lochgilphead in Scotland. A 460kW boiler, powered by locally produced
wood chips and by-product from a nearby sawmill, heats 50 one and two storey houses and
a respite home.
3.9
There does appear to be emerging government recognition of the need to provide
support to renewable sources of heat. Defra has recently awarded £16m in grants to a
number of energy saving and heating schemes. The largest recipient was Leicester City
Council, which was awarded £5.1m for a citywide community heating system. The first
phase will link Leicester University, four housing estates and sixteen council-owned
buildings. The scheme is not entirely biomass-fuelled but it contains some biomass
elements (case study 1, Appendix B). Urban schemes such as this can be less suited to
entirely biomass-fuelled schemes as the immediate availability of the materials is limited
to management of urban green spaces and biomass from the surrounding countryside.
Other fuels may therefore be necessary to supplement biomass; at least until the supply
infrastructure develops.62
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Combined heat and power
Description
3.10 For generation of electricity as well as heat, the plant requires a generator driven either by
the combustion gases or by some other working fluid. Figure 3-II shows a steam cycle
(reduced to its bare essentials). The hot combustion gases pass into a boiler where water is
evaporated to produce high-pressure steam. The steam passes through a steam turbine that
drives the electrical generator. On leaving the turbine at lower pressure, the steam is
condensed by heat exchange with cold water, and then pumped back up to the higher
working pressure. Thus the steam cycle is closed; water is only added to compensate for
deliberate venting of the steam or leaks from the steam cycle. On leaving the boiler, the
combustion gases are still at a temperature above that at which they are vented. They can
therefore be cooled further by transferring heat to circulating water, before cleaning and
emitting to the atmosphere. Bottom ash and fly ash are produced as in a heat-only plant
(paragraph 3.5).
3.11 The kind of plant shown in Figure 3-II is capable of flexible operation to vary the ratio of
heat to electrical output. To maximise heat output, the turbine can be bypassed so that the
steam goes straight to the condenser and the plant operates in “heat only” mode. However
it is then possible to bring the turbine into operation if electrical output is needed to
follow demand or support intermittent supply from other renewables. If particularly
rapid response is needed, the turbine can be partially bypassed but allowed to rotate
without driving the electrical
generator. Using CHP plant
Figure 3-II Combined heat and Power
in this way leads to very
(CHP) plant, using steam cycle for
much lower energy penalty
co-generation
than using electricity-only
plant as “spinning reserve” to
supply short-term increases
To stack
in electrical demand.
Fly ash
3.12 This kind of process is used
for relatively large scale CHP
plant: it provides both heat
(to water which can be
circulated
for
heating
purposes) and electrical
output. Steam cycles are
most efficient at relatively
large scales, and the process
in Figure 3-II is used in largescale CHP plants of the type
used in urban installations in
Northern Europe. This kind
of process is also used in
Gas
cleaning
Cool water
Heat
exchanger
Hot
water
Heated water
water
Condenser
Cold
water
Boiler
Steam
Fuel
Electrical
Combustion
chamber
Turbine
generator
Air
Bottom
ash
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
33
large-scale coal-fired electricity generating stations in the UK, where the heat transferred to
cooling water from the steam circuit is dissipated by evaporating some of the cooling water
in cooling towers that are a familiar sight at UK electricity generating stations. It is also used
in some biomass-fired electrical generation plants, such as the Fibrowatt plant at Thetford63
or the straw-fired plant at Ely64.
3.13 With a steam cycle, the proportion of the calorific value of the fuel that can be converted to
electrical output is limited by the temperatures in the steam cycle, most critically by the
steam temperature at entry to the turbine ( Box 3A). A modern coal-fired combustion plant
typically has an efficiency of about 40% in converting the energy content of the fuel to
electricity. Biomass-fired plants are typically smaller; they also give combustion gases at
lower temperatures (paragraph 3.3) so that very high steam temperatures cannot be
achieved. Consequently while their overall efficiency, including the production of heat and
electricity, can be high (typically 80% or more) their electrical conversion efficiency is
lower, and maybe of around 10% for small units. To achieve higher electrical efficiency - i.e.
higher Power Efficiency in the case of CHP plant - it is therefore necessary to dispense with
the steam cycle and use instead a gas turbine or gas engine. Rather than simply being
burned, the fuel must now be gasified or pyrolysed.
3.14 In a gasification process, air (or sometimes steam) is blown through the fuel to produce a
combustible gas (mainly carbon monoxide and hydrogen). A mixture of air and steam may
be used to control the temperature in the gasifier. Pyrolysis involves heating the fuel
without air or steam, to decompose it and drive off volatile combustible gases. Pyrolysis
inevitably leaves a carbon-rich char which may be burned or gasified. Gasification leaves
much smaller proportions of residual char.
3.15 Figure 3-III shows schematically
a gasification process. The gas
produced by gasifying the fuel is
burned with air and the hot
pressurised combustion gases
are passed into a gas turbine.
Because the turbine inlet
temperature can be higher, the
proportion of the heat released
that is converted to electricity is
higher (Box 3A). Very large
gasification plants may operate
at high pressure, to further
increase the efficiency of
electricity generation. However,
in order to protect the turbine
from corrosion and erosion, the
gases must be cleaned before
entering the turbine. Gas
cleaning may be done on the
34
Figure 3-III Combined heat and Power
(CHP) plant, using gas turbine for cogeneration
To stack
Cool water
Heat
exchanger
Hot water
Gas
turbine
Air
Electrical
generator
Combustion
chamber
Gas
cleaning
Fuel
Fly ash
Gasifier
Air or
steam
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Bottom ash
and char
BOX 3A Efficiency of energy conversion
[Summarised from Box 3A of the Twenty-second Report of the Royal Commission on
Environmental Pollution: "Energy – The Changing Climate" (2000)]
Although the first law of thermodynamics states that energy can be neither created nor
destroyed, different forms of energy are not simply interchangeable. Converting heat to
work involves using some form of heat engine (such as the steam cycle in Figure 3-II) in
which heat is supplied at a high temperature (T1) and leaves at a low temperature (T2). In
the case of the steam cycle in Figure 3-II, T1 corresponds to the steam temperature
entering the turbine and T2 to that of the water formed from steam in the condenser. The
maximum fraction of the heat entering the heat engine that can be converted to work (i.e.
electrical energy in this case) is
ηmax = 1 – (T2/T1) = (T1 -T2)/T1
Thus ηmax increases if T1 is increased. Real generating plants have conversion efficiency
substantially below this thermodynamic limit.
The fraction of the heat not converted to work (or electricity) leaves the engine as low-gradeheat.
fuel gas before final combustion, as in Figure 3-III, or may sometimes be applied after
combustion. The gas turbine drives the electrical generator directly. Heat is recovered
from the hot gases after the gas turbine, to provide the heat output from the CHP plant.
The combustion gases can commonly be vented without further cleaning. Both fly ash,
and particularly bottom ash, usually contain unburned char and must be handled
accordingly. For example, they may be co-fired with coal in a conventional generating
station. This type of plant is inevitably more technologically risky than a combustion
plant like that in Figure 3-II. It is also capital-intensive and complex, and therefore only
viable at relatively large scale.
3.16 Small-scale CHP plants require a different approach from either the steam cycle in Figure
3-II or the gasification process in Figure 3-III. The electrical generator is driven not by a
turbine but by a reciprocating gas engine, most commonly a modified diesel engine. In
effect, the combustion chamber and gas turbine in Figure 3-III are combined in the gas
engine. It is still necessary to clean the gases before they enter the engine, although the
requirements are less stringent than for a plant using a gas turbine. This must be done at the
elevated temperature of the fuel gas but not at high pressure, the technology is therefore
simpler. As in Figure 3-III, the heat output is obtained by cooling the exit gases thereby
exchanging heat into water that is circulated as the heat supply.
Combined Heat and Power Quality Assurance Scheme
3.17 New CHP facilities may attract government support under the CHP Quality Assurance
(CHP QA) scheme. CHP facilities representing significant environmental improvements
may be exempt from the Climate Change Levy (CCL) provided they meet certain
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
35
performance standards. This is not relevant to biomass-fired plants, which automatically
qualify by using a renewable fuel. However, Enhanced Capital Allowances (ECAs) may also
be claimed based on the plant’s Quality Index (QI), a measure of overall efficiency
(paragraph 3.19), and Power Efficiency which is defined as the proportion of the (gross)
calorific value of the fuel converted to electrical output.
3.18 Both the Power Efficiency and QI thresholds to qualify for ECAs have been set at levels
intended to encourage biomass-fired CHP, implicitly recognising the particular
characteristics of biomass specifically that the proportion of the calorific value that can be
converted into electrical output is lower than for other fuels (paragraphs 3.3, 3.13 and Box
3A). Plants fuelled solely by biomass must achieve a Power Efficiency of 10% or more and
also reach a required QI threshold, both based on total fuel burned and electricity
despatched over a 12-month period. By comparison CHP units using more conventional
fuels must achieve a power efficiency of 20% plus a more stringent QI threshold.
3.19 The QI is “an indicator of...energy efficiency and environmental performance...relative to
the generation of the same amounts of heat and power by separate alternative means”65. The
definition of QI in the CHP QA standard recognises differences between fuels and scales of
operation, including the particular characteristics of biomass: biomass-fired plant is set a
threshold which is very much lower than that for large gas-fired plants, significantly lower
than for small gas-fired plant and marginally lower even than that for plant fired by
alternative fuel gases or biogas.
3.20 Thus the existing CHP QA standard appears to provide incentives for new biomass-fired
CHP installations, although they need to be complemented by incentives for renewable heat
production (see below). The requirement to meet even the 10% threshold for Power
Efficiency calculated for average performance over a year however, could act as a barrier to
using CHP plant as “spinning reserve”. We recommend that the government undertake or
commission a study to investigate whether the existing Power Efficiency standards are
appropriate and, if necessary, modify the CHP QA standard to promote the use of CHP
as “spinning reserve” to back-up intermittent renewables. The study should also review
whether the thresholds should be based on the gross or net calorific value of the fuel (page 30,
footnote iii).
Practical application
3.21 CHP plants burning biomass as a fuel are not common in the UK. The BedZED
development in South London (Box 2D) has a small biomass gasification plant at its centre.
Some technical problems have been experienced, primarily with gas cleaning (Figure 3-III),
but the indications are that these problems are short-term. Also, the scheme being
developed by Leicester City Council (paragraph 3.9) is likely to include 6MWe of biodieselpowered CHP in its later stages. There are other examples of CHP plants using biomass or
biofuels, but use of the technology in the UK is far behind deployment in other Northern
European Countries.
3.22 This is partly because output-based government support for renewable energy is only
available for electricity generation (Appendix A) but also because biomass-fired plants are
36
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
less easy to operate than, for example, gas-fired. Relatively small heat-only plants can be
tolerant to fuel inconsistency and moisture but larger plants, and particularly gasification
processes operating at high pressure (Figure 3-III), require dry fuel with consistent
properties, including particle size. Fuel preparation and drying then presents an additional
expense if forest co-products or SRC biomass is to be used. Sawdust or wood-dust pellets
break down to give a particularly free-flowing material. Domestic scale plants require
consistent free-flowing fuel for automatic operation, and therefore many operators and
most domestic users would prefer to use the more costly sawdust pellets than cheaper but
less consistent willow chips or forestry residue.
3.23 Although sawdust pellets are becoming an internationally traded commodity, supply
chains are not yet sufficiently established in the UK to guarantee a reliable source of fuel.
Potential developers may therefore be discouraged from investing in CHP because of the
lack of available and consistent fuel. Some developers have resorted to using local forestry
resources until supplies of pellets are available but this can cause problems with technology
that is designed for a drier, more homogeneous fuel.
Heat demand and CHP
3.24 The viability of heat and CHP schemes at larger than domestic scale relies on a market for
the heat output, which in effect means that they are tied to a building, a factory or a heatdistribution network. In Scandinavia such networks have been established, and experience
there shows that a heat distribution network can extend economically for tens of kilometres
and reach tens of thousands of homes and other premises. There are over 600 community
heating schemes in the UK, some of which already utilise CHP66. We recommend that the
councils or organisations that own these networks should be encouraged to
incorporate biomass elements using local resources wherever possible when upgrading
the systems.
3.25 There are also possibilities to develop new applications for CHP plants within an emerging
biomass sector. The heat output can be used for drying biomass, for production of pellets to
be utilised in other plants. Production of some biofuels for transport also represents a heat
demand, for example the distillation of bioethanol. This demand can be met by straw-fired
CHP.
3.26 For larger biomass power installations of the order of 10MWe and above, finding a 1030MWth heat demand to enable the plant to run in CHP-mode is less easy today than it
was 10 years ago. The UK has continued to de-industrialise, and there are now fewer singlesite heat demands available. In addition, many suitable sites such as petro-chemical plants,
airports and car factories already have gas-fired CHP systems in operation. Some sites do
remain however, and new opportunities are emerging with significant housing, retail and
industrial park developments. Retail sites find connection to a district heating system
especially attractive because it removes the need to allocate potentially profitable retail
space to a heat plant.
3.27 Community heating, utilising both existing small and larger systems, as well as developing
new schemes, provides a significant opportunity for biomass heating. For existing schemes,
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
37
replacing fossil fuel boilers with biomass heating boilers is a relatively simple and
economically viable option, subject to an adequate and reliable heat demand and sufficient
capital grants. Bristol City Council is considering this option for a council-owned housing
block currently fuelled by natural gas (case study 4, Appendix B).
3.28 While there is no central database of heat demands in the UK, research for the Community
Energy Programme run by EST and the Carbon Trust has begun to map heat demand
across the UK67. These include domestic buildings, hospitals, higher educational
establishments, factories, warehouses, offices and retail premises, central government
buildings (including prisons, Ministry of Defence buildings, and offices), hotels, leisure
centres, and schools.
Table 3.1 Fossil fuel use for electricity and heating
Fossil Fuel Use for Space Heating
and Domestic Hot Water
Electricity Use
Hospitals (kWh/bed)
25,740
7,000
Universities (kWh/full time student)
4,200
1,710
Factories (kWh/m2)
245
471
Local Government Offices (kWh/ m2)
95
39
Commercial Offices (kWh/ m2)
147
95
Retail (kWh/ m2)
185
275
Warehouses (kWh/ m2)
64
81
Hotels (kWh/bedroom)
13,620
6,387
Schools / Further Education (kWh/pupil)
2,583
372
Leisure Centres (MWh)
2,350
650
1
This figure does not include process electricity
3.29 The findings of this research have been separated into heat and electricity requirements by
sector; this is illustrated in Table 3.1. It demonstrates that hospitals and hotels are
important opportunities for biomass district heating and CHP, providing stable heat
demand and utilisation levels. Universities, schools and leisure centres provide other good
heat demand levels, while those for offices and warehouses are less attractive. It also
38
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
illustrates that far more energy is consumed for heating these buildings than for direct
electrical requirements. It is therefore logical for heat to be the driver of a CHP facility
where there is sufficient demand. Replacing fossil fuel-powered heat therefore offers
opportunities for much higher CO2 savings than replacing the electricity. The current
government incentive schemes fail to recognise this despite the fact that this would be an
extremely effective way of achieving the CO2 reduction targets that it has set.
3.30 All new housing, office and other building developments provide opportunities for
biomass heating and CHP. All boiler replacements offer similar opportunities, particularly
in areas away from the natural gas grid (paragraph 3.6). At present however, the level of
awareness amongst developers, designers, financiers and users on the potential for biomass
energy is low. Significant informational campaigns are necessary, as well as targeted
marketing programmes for local authority staff and elected members, developers and the
private sector. With significant new housing developments planned across the UK
(paragraph 4.18), as well as new and refurbished hospitals, schools and other public
buildings, every development where district heating and CHP for both biomass and fossil
fuels is not assessed is an opportunity lost for saving CO2 emissions. We recommend that
all new housing schemes and mixed industrial/retail/housing developments should
assess district heating and CHP opportunities, including the opportunity to use local
biomass fuels. Positive planning policies should require these developments to include
biomass district heating and CHP wherever it is feasible (paragraph 4.19).
3.31 To make both current and additional sites attractive for CHP in future, greater incentives
will be needed for ‘green heat’, comparable to those for renewable electricity (Appendix A).
Whereas green power can attract a price of 6.5-7p/kWh in total, green heat can attract an
income of only 1-1.5p/kWh68. This encourages the development of the less efficient green
electricity market at the expense of the more efficient green heat market, so that electricity
is currently the usual driver for CHP and heat output is often wasted. Heat output needs to
become a significant driver to promote more widespread use of CHP, especially in plants
that can be used as “spinning reserve”.
Green heat credit
3.32 It has become clear to us that the most obvious gap in current support schemes is the
lack of any mechanism for supporting the generation of renewable heat energy,
comparable for example to the RO scheme for renewable electricity. We recommend
that the government introduce such a support mechanism. It could act as a major
stimulus to both biomass heat and biomass CHP, and it is unlikely that these renewable
energy forms will increase significantly without it. The mechanism could be set up along
the lines of the Renewables Obligation, and oblige current heat suppliers (gas, oil and
electricity) to supply a given proportion of their heat from renewable sources by a set date
(for example, 2% by 2010 and 5% by 2020). The Renewable Heat Obligation could either
relate only to biomass, or include other technologies such as solar hot water panels; the
percentage obligation would depend on which technologies were included. Certificates of
verification of supply could be administered in a system analogous to the Renewables
Obligation Certificate system as Heat Obligation certificates - HOCs.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
39
3.33 We have recommended the introduction of a ‘green heat’ credit as a policy measure that would
fit naturally with the government’s current policy and actions to promote renewable energy.
However, we note that an approach based on taxation of CO2 emissions would promote all
renewable energy sources, would require fewer specific measures and would automatically
promote heat as well as electrical output. The introduction of the EU-wide emission trading
system will favour biomass along with other renewable energy sources, but whether the price
will be high enough to provide a serious incentive remains uncertain at this stage.
Electricity generation
3.34 Unlike heat-only and CHP facilities, operations that generate only electricity avoid the
need to locate generation facilities adjacent to demand. Electrical power lines are cheaper to
install than heating networks and are more versatile, and where the plant is situated near the
national grid the generator can sell any surplus power on the open market. The cost is the
loss of efficiency by not utilising the heat output from the plant. For example, the Forestry
Commission has estimated that some 440MW of power would be available from existing
biomass resources (paragraph 2.76) - this would however forfeit 1400MW if the heat was
not also used. At present only electricity output qualifies for credits under the
government’s Renewables Obligation scheme, which is why this has attracted more
investment than district heating or CHP (Appendix A). There are two approaches to
electricity-only generation from biomass: gasification and co-firing.
Gasification of energy crops - ARBRE
3.35 The Arable Biomass Renewable Energy (ARBRE) plant at Eggborough in South Yorkshire
was an example of the kind of process shown in Figure 3-III: gasification of the fuel
followed by combustion into a gas turbine, with high turbine inlet temperature to
maximise the efficiency of conversion to electrical energy. The fuel comprised agricultural
residues and SRC willow chips. The plant was designed for electrical output only, with the
heat dissipated by water evaporation in cooling towers. Some aspects of the project were
outlined in the Twenty-second Report.
3.36 Although the ARBRE initiative eventually collapsed, it nevertheless illustrated many of the
infrastructure features essential for a successful biomass energy scheme. The ARBRE
project involved a group of farmers growing willow and selling it to a dedicated biomass
energy plant with long-term contracts. Kelda (originally Yorkshire Water) was investigating
the potential for using sewage sludge as a fertiliser.
3.37 The ARBRE plant experienced some technical difficulties, specifically due to deposits that
fouled and ultimately blocked the heat exchangers. These should not have been sufficient
to jeopardise the scheme but the investors were unable to underwrite the costs of
completing the start-up programme and bringing the plant into full operation. The failure
of ARBRE had implications considerably beyond that single operation: Kelda saw it as a
potential pilot for a further 10 such plants whose future is now in serious doubt, while the
Swedish company from whom the technology had been licensed saw it as an important
demonstration. But the loss of ARBRE has also shaken the confidence of other investors
and, equally importantly, of the farmers concerned.
40
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3.38 One of the original difficulties at ARBRE lay in securing a stable funding base for this
experimental project. It was planned and built under the Non-Fossil Fuel Obligation
(NFFO), which guaranteed demand and price for the electrical output but ignored the
potential heat output and gave no assistance with the capital expenditure. The Renewables
Obligation has now replaced NFFO but nevertheless many of the features of NFFO
remain, specifically in focusing on electrical output but giving no credit to heat. The lack of
success so far in introducing this technology seems to be a UK-specific problem, given the
success with which biomass energy plants are operating in other Northern European states,
and this suggests under-resourcing of this critical pilot stage. ARBRE cost £28m69 to build,
but a properly operating plant would generate revenue and would be attractive to investors
if underwritten; it would also lead the way for further investment.
3.39 The government’s emphasis on high-technology, capital intensive plant, concentrating on
electrical output and aiming to maximise the potential export value of the technology
(paragraph 1.10), inevitably means that biomass energy will experience a few false starts
(such as ARBRE). Furthermore, given that the UK process plant sector shrank to a small
size some decades ago, most of the equipment is fabricated outside the UK so the potential
export earnings are limited. The focus should therefore be on establishing the sector
through the use of existing, proven technology whilst simultaneously developing new
technologies and demonstration plants. We recognise the value of innovation but stress
that it must be developed against the backdrop of a secure, stable sector that can operate
independently of these new developments until they are proven; the very successful
development of the wind sector in Denmark illustrates this approach. Waiting for high-tech
approaches to be developed merely delays the development of the entire sector.
3.40 The Bio-Energy Capital Grants Scheme (Appendix A, paragraph A.8) has so far been too
focused on new technologies. We recommend that the scheme is expanded and its
guidelines revised to make clear that its main purpose is to support the installation of
biomass-based combustion equipment to bring about a large-scale expansion of heatonly and CHP generation from biomass (power-only generation should be excluded
on efficiency grounds).
3.41 We recommend that the government underwrite the cost of at least one, but preferably
several schemes to demonstrate the commercial viability of medium-scale biomass
energy projects. Future schemes should however be designed to utilise their heat
output as well as electrical power.
Co-firing
3.42 With slight modification, coal-fired power stations can accept a proportion of processed
biomass (usually as sawdust) blended into the fuel. A number of plants in the UK currently
co-fire a variety of biomass materials, including that from energy crops, to produce
electricity and consequently qualify for Renewables Obligation Certificates (ROCs).
3.43 Co-firing, unlike the use of biomass on its own, produces net CO2 emissions from the
combustion process, because of the coal in the fuel mix. These emissions are less than if the
coal had been burned alone, but the overall contribution of carbon to the atmosphere is still
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
41
positive. Partly because of this the ROC system places limitations on output from co-firing
to prevent companies focusing on this one, easier form of renewable energy at the expense of
investment in renewable technologies that avoid fossil carbon emissions altogether.
Grades of biomass
3.44 Biomass for co-firing is classified as low-grade or high-grade according to calorific value.
Sawdust is low-grade as it has a high moisture level and hence a low net calorific value. It can
be co-fired without drying because it will be mixed with coal, but the heat released per
tonne will be less than for drier material. This is not just because part of the mass (the
moisture) has no calorific value but also because of the heat consumed in evaporating the
water. High-grade biomass is produced by drying and processing (into pellets, for example),
but is more expensive and better suited to domestic heaters and 100% biomass-fuelled
operations (paragraph 3.22).
Blending
3.45 The fuel for co-firing is prepared by blending coal and sawdust. Sawdust already has a high
moisture content (paragraph 3.44) but has a capacity to absorb further water if not kept
under cover. Consequently the capital costs of providing storage for sawdust is high. This
could be minimised by providing central facilities for the blending and storing of fuel,
servicing several generating facilities. However, Ofgem claims that under current rules fuel
that is blended off-site is not eligible for ROCs. So for now, co-firing plants must blend
their own fuels on site, or inject coal and biomass to the combustion chamber separately.
Therefore, power generators wishing to co-fire must invest in costly storage and blending
facilities. If they are unable to recoup this capital expenditure by 2016 (when co-firing
ceases to be eligible for ROCs) they may choose not to co-fire at all. This is a significant
obstacle to the development of co-firing.
3.46 We have heard a number of arguments from Ofgem to justify this situation. We have heard
concerns about the difficulty of maintaining audit trails across long distances (some
sawdust is imported), about the difficulty of sampling blended fuels to check their
composition, and even the concern that sawdust will blow away during transport. We are
not convinced by the arguments and consider that the current arrangements for blending
are unnecessarily restrictive. We therefore recommend that possibilities for secure
arrangements be investigated whereby Ofgem can certify blended fuels for co-firing as
eligible for ROCs at sites other than the power station that is going to use them.
Role of co-firing
3.47 Current government policies encourage and reward co-firing of biomass and fossil fuels in
existing power plants, but, correctly in our view, co-firing is treated as a transitional stage in the
process of replacing fossil fuels that allows a biomass industry and infrastructure to develop.
We will return to this point in chapter 4. However, we note that some of the more prominent
schemes we have examined that use biomass alone are failing or delayed, albeit for wellunderstood and rectifiable reasons. The technology might take longer to develop than so far
anticipated and the need for co-firing is, therefore, likely to need to remain a part of UK energy
production for longer than is currently foreseen by government. In particular, the capacity to
42
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replace co-firing with completely biomass-fuelled power production is likely to remain limited
beyond the 2016 deadline for the end of co-firing. We recommend that the 2006 review of the
Renewables Obligation takes this into account when assessing its deadlines.
Environmental implications
3.48 Combustion plants of any description have environmental effects, resulting from their
gaseous emissions, solid wastes, physical intrusion, noise and transport. Any strategy that
envisages the construction of several hundred new wood-burning plants requires a careful
assessment of the consequences of their effects on the physical environment and of the
reaction they will engender in people living near them, or who might otherwise be affected.
The strategy will need to include arrangements for minimising pollution and intrusion, and
gauging and addressing public concerns.
Emissions
3.49 A heat producing plant needs a local heat distribution network servicing its customers. This
will usually mean constructing the plant reasonably close to housing or commercial or
industrial premises that can make use of the heat. This implies that particular attention
needs to be paid to emission control, for reasons both of public and environmental health
and of public acceptability. Gas cleaning and particulate removal technologies are readily
available, and would be incorporated into the initial design for new-build facilities.
Condensers and re-heaters can be fitted to remove steam, plumes of which are unsightly but
do not otherwise affect the environmental impact.
Figure 3-IV Regulated pollutant emissions from Swedish CHP plant
70
fuelled with biomass or coal
1.2
VOC
CO
NOx
PM
SO2
g/kWh
1.0
0.8
Volatile Organic Compound
Carbon monoxide
Nitrogen oxides
Particulate matter
Sulphur dioxide
0.6
0.4
0.2
0.0
VOC CO NOx PM SO2
Biomass Technology
VOC CO NOx PM SO2
Reference Technology
Fuel production
Conversion
Clean-up
Conversion/indirect
3.50 The emissions of most concern (Figure 3-IV) are Volatile Organic Compounds (VOCs).
Carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), sulphur dioxides
(SO2) and chlorinated organics (principally dioxins). In gasification plants, the gas can be
treated before combustion to remove VOCs. Carbon monoxide emissions are low if the
combustion conditions are adequately controlled. Lower combustion temperature
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43
compared to other fuels (paragraph 3.3) means that the production of nitrogen oxides is
lower. Well designed and operational gas cleaning equipment filters particulate matter and
thereby concentrates heavy metals into the fly ash (paragraph 3.54). The sulphur content of
wood is much lower than coal, leading to much lower sulphur oxide emissions. Thus,
compared on the basis of electrical output, biomass leads to generally lower emissions than
coal; example data from Sweden are shown in Figure 3-IV.
3.51 Chlorinated organic emissions can arise if the fuel contains chlorine. Many forms of
biomass have very low chlorine content, and therefore give rise to very low quantities of
dioxins. However, the presence of chlorine in the biomass can lead to dioxin production.
Therefore timber treated with organochlorine wood preservatives, or wood mixed with
PVC, should not be used as a source of biomass fuel in the sorts of generators being
described here. Such materials would be classified as waste (paragraph 2.73) and should be
burned only in a properly authorised waste incinerator. The combustion of virgin wood will
result in the formation of much lower levels of dioxins, but even these small quantities have
the potential to be significant on the scale of wood burning that would be necessary to meet
the targets for biomass energy that we have proposed. It is important, therefore, to ensure
that wood-burning heat and power plants are designed to reduce dioxin levels to the lowest
practicable level. Guidance on best available technology for firing installations for wood
and biomass is being prepared by the Expert Group on Best Available Techniques of the
Intergovernmental Negotiating Committee of the Stockholm Convention on Persistent
Organic Pollutants71.
3.52 A modern wood burning plant should, therefore, with careful design, be able to meet all air
pollution control standards at reasonable costs. Even so, siting of the plant must be carried
out with care, and in particular it is important that biomass plants should not be located in
areas where they would exacerbate existing poor air quality. Plant burning any fuel in a
boiler or furnace with a net rated thermal input of 50 megawatts or more is authorised by
the Environment Agency (SEPA in Scotland and the Environment and Heritage Service in
Northern Ireland) under the Integrated Pollution Prevention and Control (IPPC)
regulations Part A. All plant involving pyrolysis, gasification or other heat treatment of
carbonaceous material would also fall under Part A. Plant with a thermal input of between
20 and 50 MW would be authorised by local authorities under IPPC Part B73. Emissions of
nitrogen oxides may represent a significant contribution to poorer local air quality. On the
other hand, in some areas, heat made available from a biomass plant could displace more
polluting heat sources (paragraph 3.6).
Solid Wastes
3.53 The amount of ash produced when plant material is combusted generally lies between 616% of dry weight, although it may be as low as 1%74. Although much of the variation can
be attributed to plant species, growth conditions also play a major role. Apart from heavy
metals, considered below and in chapter 2 (paragraph 2.29), the major components of the
ash are usually potassium and phosphorus. For this reason, wood ash is often used as a
fertiliser. However, the proportions of these and other substances vary widely, resulting in
the pH of the ash ranging from almost pH neutral to distinctly alkaline. This variation is
often affected by the major nitrogen source used by the plants75.
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3.54 Because of their behaviour in combustion plant, some metals exit primarily in the fly ash;
this includes metals with high toxicity, including cadmium, mercury and lead. Figure 3-V
illustrates this (see also case study 2, Appendix B). The volume of fly ash from the facility is
much smaller than that of the bottom ash. Therefore the proportion of these metals is very
much higher in the fly ash than in the biomass. In effect, the process concentrates the
metals into the fly ash, which can then be consigned to a sealed landfill. The bottom ash
from which these metals have been depleted can be returned to the land where the crop is
grown, or put to some other use such as inclusion in cement or other construction
materials. This process is illustrated for willow in Figure 3-V using cadmium as an example
but it could be applied equally to other heavy metals and other energy crops. Long-term
build-up of metal levels in the soil would depend on continuous addition of a fertiliser with
a high heavy metal content - usually sewage sludge. The use of bottom ash or sewage for
land conditioning would need to comply with regulatory or advisory limits on metal inputs
to soil.
3.55 Co-firing of biomass with coal leads to mixed ash in which the coal minerals dominate. This
contains constitiuents that prevent it from being returned to the soil. As a result, the soil
used for biomass production may suffer long-term depletion of key elements, notably
nitrogen, so that increased inputs of agrochemicals may be needed.
Figure 3-V Ash recycling
Cadmium
in fuel
Uptake by
willow
Bottom ash
(small amount
of cadmium)
used as fertiliser
Cadmium from
sewage or
fertiliser
Fly ash
(most of cadmium)
to secure landfill
Cadmium
already
in soil
3.56 Bottom ash from certain combustion processes can be used as a construction aggregate - for
making cement or breezeblocks, for example, or returned to the soil as fertiliser. Ash from
power stations and from municipal waste incinerators is used in this way, and this is clearly
a more satisfactory way of dealing with ash than landfilling. It is important, though, to
ensure that fly ash, with its higher metal content, does not find its way into use either as a
fertiliser or an aggregate.
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45
Intrusion
3.57 A programme of construction of new small to medium heat or CHP plants, incorporated
into new housing or light industry developments, offers an opportunity for sensitive and
innovative design. Modern biomass stations need not be ugly, and it is desirable, if they are
to gain public acceptance, that they are well designed. The building needed to house a small
to medium sized installation need not be large or intrusive. The generator at BedZED
(Box 2D) is housed in a building the size of a small house, and is incorporated sensitively
into the development. The wood-chip store and heat generating plant at West Dean
(paragraph 3.7) is the size of a substantial agricultural shed, but sensitive planning has
ensured minimal aesthetic impact of the plant; the chimney is camouflaged and walls
sympathetic to neighbouring buildings improve the appearance of the plant. At both West
Dean and BedZED, potential planning problems were avoided through discussion with
those who would be affected by the building of the plant. The 36MW straw burning plant
at Ely, Cambridgeshire incorporated a number of measures to reduce the visual impact of
the plant76, including sinking the plant to 8m below ground level. The surplus clay removed
during construction was used to build soundproofing landscape features that were planted
with 12,000 mixed trees and shrubs and this is now used as a public recreational area.
3.58 Generators, particularly those powered by reciprocating engines, are inherently noisy, but
to be acceptable to the community the local power plant must be close to silent. It is
essential to design a high level of noise control into a scheme from the outset. At West
Dean, noise problems were avoided by restricting the chipping to times when it would
cause minimum disturbance. At BedZED, the plant is located close to the main buildings
but has been adequately soundproofed so that no noise complaints have been made.
Conclusions
3.59 The properties of biomass make it a particularly appropriate fuel for heat and CHP plants.
Technologies for biomass-fired heating plants are well established; applications depend on
matching biomass supply to heat demand. CHP technologies are controllable but further
development is needed, particularly for small-scale plant and plant with high efficiency of
conversion to electrical output. Co-firing of biomass with coal in existing generating
stations has an important short- to medium-term role in developing the biomass sector.
Biomass plant that are well designed and properly operated are associated with lower
emissions than other fuels, notably coal. Handling of the ash, including recycling of
nutrients to the soil, requires attention for any substantial application along with
minimising the impacts of traffic movements and the visual impact of the plant itself.
3.60 Government policy should concentrate on the development of the biomass sector in the
UK rather than speculative export opportunities. The plethora of existing schemes should
be replaced or supplemented by coherent policies to promote efficient heat production
and use, particularly ‘green heat’ from biomass. Unintended barriers to the use of biomass,
for example in co-firing, need to be removed.
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CHAPTER 4 - MEETING THE TARGET
4.1
To meet the targets recommended in our Twenty-second Report we proposed that between
3 and 16 GW should be derived from biomass (paragraph 1.15). In this chapter we calculate
the number of biomass conversion facilities that would be needed to meet this target and
consider sources of wood to fuel them and the land area needed for growing energy crops
during each of the four stages of development that we recommended in Chapter 2
(paragraph 2.41). We also consider transport implications and, perhaps most critically, we
investigate ways of gauging likely public attitudes to this form of energy and incorporating
values into decision-making.
Economics of Biomass
Fuels
Willow
4.2
In appropriate circumstances, an established willow coppice could bring returns equivalent
to those from some arable crops while utilising relatively low-grade land. However, the
initial investment required to establish a crop, purchase planting and harvesting machinery
and secure a market, can currently be prohibitive. Farmers are unable to grow energy crops
without both financial assistance and guaranteed demand for the crop. A number of
government schemes offer financial assistance for planting energy crops (Appendix A) but
these are very limited in the extent to which they can provide the necessary security. There
is potential for these costs to fall, since with larger areas of energy crops, the relative
machinery costs for each farmer will fall, and efficiencies in harvesting and collection will
also improve. Yields are also likely to improve through better management and higher
yielding willow stocks, perhaps by 30%. However, cultivating willow and other SRC crops
will continue to be risky for farmers unless the government can bring forward better
arrangements for financial assistance and promoting long-term contracts.
4.3
Assessing the overall economics of energy crops is problematic at this stage of development,
due to the limited experience in both growing the crops and utilising them in power or
heating systems, (less than 2,000 hectares (ha) of energy crops are currently being grown in
the UK, producing around 17,000 odt of fuel a year). A number of factors are critical in
assessing the overall economic viability for farmers of growing the crops. These include:
• Crop yields
• the level of grants available for establishing the crop
• set aside payments for land used
• the costs of maintaining and harvesting the crop
• the market for the fuel and payments made for it
• costs of removing the crop at the end of the growing cycle.
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47
48
4.4
The establishment grants for energy crops from Defra are between £920 and £1600/ha,
depending on the crop and former land-use. In addition, set-aside payments can continue
to be claimed. Alternatively 145/ha for energy crops is available from Common
Agricultural Policy (CAP) funds (but the total fund available is restricted and in practice
payments may be significantly lower than this). Scottish farmers qualify for additional setaside allowances if they use all of this land for energy crop production. Despite the
combination of these funds, there has been slow uptake of energy crops in the UK, mainly
due to the lack of a market for the fuel and long-term farmer security.
4.5
A recent analysis of the potential income over a 16-year period for both willow SRC and
miscanthus suggested that for medium yield land the average annual income would be
£187 to £360/ha77. This compares poorly to a wide range of food crops and livestock. Most
of the current energy crops are grown on set-aside land, this payment is important in
making the economics of energy crops viable. A report for the DTI that reviewed the
economic case for energy crops in the UK confirms this conclusion, it concluded that:
based on current yields, our estimates of the gross margin for the farmer suggest that energy crop
production is only attractive using set-aside land78. At current yield levels SRC willow is less
attractive than barley, oats or winter wheat. The DTI commissioned a further assessment
that showed that with a 30% increase in yield, energy crops would be an attractive
alternative to barley. Without subsidies an economic case cannot currently be made for
energy crops but carefully designed additional subsidies could encourage further uptake of
energy crops by UK farmers. The critical issue for farmers is the security of a market for at
least two to three crops. Without that the risks of establishing a crop with a lifetime of 15-20
years is too great.
4.6
Planting grants are currently paid in one lump sum after planting. The first harvest takes
place after four years of growth and for these four years farmers will not be receiving any
income from those areas of land under SRC production except for set-aside payments. If
guidelines on the planting of different ages and species are followed, farmers should then be
able to attain an annual income from the crops. We recommend that Defra consider
introducing growing grants for the first three years of an SRC plantation to improve the
financial viability of the crop for farmers. We also recommend that the government
offer long-term security to farmers by ensuring that should their local market for SRC
collapse, they will be able to receive payments for keeping the crop until the end of the
15-20 year SRC lifespan (paragraph 2.38).
4.7
The Commission has received evidence that higher payment levels to farmers would
make energy crops more attractive. However, the over-riding conclusion was that the
critical element in improving both the economics and the commitment of farmers to
energy crops was security of demand. We believe that if farmers had confidence that at
least two, and ideally three, crops were guaranteed a market at a reasonable price, many
would make a commitment to the crop. Unlike annual crops, where low prices one year
would be likely to lead a farmer to planting an alternative crop the next, SRC willow and
miscanthus require commitment to a long-term crop on at least a 16-year cycle. Although
miscanthus is on a shorter growing cycle with annual cropping, it is quite difficult to
remove the rhizome roots once established so that miscanthus too must be viewed as a
long-term option.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
4.8
This assertion is confirmed by recent initiatives from the UK company Biojoule, part of the
AEA Technology Group. Biojoule is seeking to provide fuel for the co-firing market.
Biojoule have offered a simple contract to a number of farmers to test this market. The key
ingredients of the contract are:
• an agreement to purchase at least two crops with an option on further crops,
• an agreed minimum price, with further financial incentives to increase the yield from
a minimum level of 4 odt/ha/year,
• commitment to take on the harvesting and sale of the crop.
This contract was offered to farmers surrounding a large coal-fired power station and over
300 ha were offered for energy crop planting in Spring 200579.
Comparative prices of biomass fuels
4.9
Energy crops are relatively expensive compared to other biomass fuels. There are three
distinctive groups and price bands of fuels:
• Waste arisings attract a ‘gate fee’ if sent to landfill instead of being used as a fuel. Costs
to the generator are up to £15/odt. These are by far the cheapest fuels and may in fact
come at negative cost, depending on transport costs and gate fees.
• Forest residues, timber industry off-cuts and arisings and agricultural residues such as
straw are typically in the range of £15-35/odt. These are ‘medium cost’ fuels, and
transport costs here are quite critical to overall costs. Sawmill and related timber
processing industry products used on-site would likely be at the lower end of this price
range.
• Energy Crops, wood pellets and wood chips produced from roundwood and having
to be transported more than 8km are the more expensive fuels. Fuel prices here are in
the range of £40-80/odt but as yields increase and production and distribution
infrastructure develops this would be likely to decrease.
4.10 Energy crops thus cannot currently compete on price against the other two groups of
biomass fuels. Energy crops do however have the potential to provide very significant
volumes of fuel. In the event of significant growth in the use of biomass for heat and power,
resource limitations may be faced for the other fuels. In order to use the dual heat and
power benefits of biomass energy to help reach CO2 reduction ambitions, energy crops will
be needed in significant quantity. As supply increases, prices are likely to drop to a more
competitive level.
4.11 However, overall, with the exception of mains natural gas, biomass is currently cheaper
than all other competing fuels. Even when set against natural gas, some of the cheaper
biomass fuels can compete successfully (as is shown in the worked example in case studies
5 and 6 in Appendix B). Gas prices are also increasing at present, a trend likely to continue
over the next few years; hence the balance could shift towards wood heating. Biomass also
offers the additional benefit of a secure, controllable supply of domestic fuel that is not the
case with other intermittent renewables or imported fossil fuels.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
49
Capital and generation costs
4.12 Compared to fossil fuel heating technologies, biomass plant is more capital intensive by a
factor of 2 to 3; savings for a project come through cheaper fuel. While there is a significant
potential for capital cost reductions, this will require large volumes of sales and a reliable
supply chain in the UK. Even with reduced costs due to volume sales, there would still be a
capital cost gap between wood heating technologies and current fossil fuel technology.
Capital grants are available through several sources (Appendix A) to reduce the impact of
this higher initial cost but as yet they have been unable to stimulate large-scale take-up of
the technology.
4.13 Table 4.1 shows the comparative capital costs of biomass and fossil fuel technology for
electricity and heat production. It is evident that biomass heating is cheaper per kW
installed than any of the power options, but the return from heat sales is correspondingly
low. Biomass power costs are higher for the reasons discussed above.
Table 4.1 Installation costs of generation technology
Technology
Size
£/kW installed
Biomass Heating
>1MWth
£70
Biomass Heating
>300kWth
£100
Biomass Heating
<300kWth
£200
Gas fired CCGT
150MWe
£400
Gas Fired CHP
750kW-1MW
£600 - £700
600MWe
£1,000
Steam Turbine Biomass Power
5MWe - 40MWe
£1,400 - £1,800
Gasification Biomass Power
5MWe - 40MWe
£1,500 - £2,000
Biomass Power
5MWe - 40MWe
£1,800
10MW
£4,400
Pulverised Coal Power
Pyrolysis Biomass Power
4.14 For gasification and pyrolysis plant (until recently the technologies favoured by the DTI for
capital and R&D grants), the costs of the plant are speculative as they are still at the
demonstration stage. The only example of a large-scale gasification plant in the UK, for
example, was the ARBRE project, which failed as we have described above (paragraph 3.38).
50
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
4.15 Site-specific capital grants are available for some biomass power stations. Five grants have
been awarded since February 2003 for plants ranging from 2.5MWe to 23MWe. Most of
these grants include a requirement to take a growing level of energy crops as a fuel source.
However, none of them had definitely gone ahead or received full financial backing by
early March 2004. The CHP Quality Assurance scheme can in principle provide Enhanced
Capital Allowances (paragraphs 3.17 - 3.20) but it is not clear whether this has actually
materialised.
4.16 While capital grants can help in reducing the high up-front costs of such systems, it seems
that under current policy conditions only those plant that are able to utilise either very
cheap or zero cost fuels (i.e. plants using fuels for which they can charge a gate fee) are likely
to go ahead. Dialogue with industry representatives has indicated that for power plant using
either forest residues or energy crops, there is a 1-1.8p/kWh gap between the price
chargeable for electrical output and the income necessary for economic viability80.
4.17 The household use of fossil energy currently attracts a 5% rate of VAT. Some energyefficiency equipment now also attracts that rate. In addition to an increase in capital grants
for biomass installations, we recommend that the rate of VAT on biomass-generation
equipment for final users also be reduced to 5%. This could help to stimulate the take-up
of small-scale biomass generation (domestic pellet heaters for example).
Effective markets
4.18 Biomass energy is most economically viable when the heat potential is exploited. This is
most effectively achieved by locating heat and CHP plants so that they can be linked at
reasonable cost to heat-distribution networks. This implies that new-build residential areas,
hospitals and industrial complexes are the most likely applications for biomass energy
facilities (paragraph 3.29). The Office of the Deputy Prime Minister (ODPM) has
announced its intention to build almost 1.2 million new homes by 2016 under its
Sustainable Communities programme. The Sustainable Communities programme cannot
be truly sustainable without some degree of renewable energy supply. Biomass could be a
part of this if the water and land availability for energy crop growth and other
environmental factors are favourable. In our view, if the ODPM programme goes ahead
the use of sustainable energy production should be an integral part of
the design.
4.19 Distributed heating networks can be incorporated into residential estates most costeffectively at the initial design stage. The project at Leicester (case study 1, Appendix B)
demonstrates this, though the Leicester initiative will also cater for an element of retrofit in
existing premises. Using biomass as a fuel will not always be feasible in all locations.
Nevertheless in many new-build situations there will be scope for securing supplies of
biomass in an environmentally sound way within a reasonable distance. Where this is not
possible, the use of other fuels to power CHP would be more efficient than centralised
electricity-only generation. Accordingly, we recommend that the ODPM encourage
councils and developers to incorporate CHP and district heating as standard in all of its
new-build projects, fuelled by biomass wherever possible. Councils should consider
biomass CHP or district heating as an option in all retrofit projects. To aid this, we
recommend that an integrated approach that takes account of all available biomass
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
51
resources in a region should be included in the spatial plan for the region81. A new
Forestry Commission supported website provides relevant information, which should
prove a useful tool for such an analysisv.
4.20 Further steps will be needed if the full potential of biomass for district heating and CHP is to
be realised. We recommend that financial support be awarded to councils to enable them
to investigate the potential for biomass energy in their area. Taking the European Union’s
leadvi, underwriting loans for biomass schemes where councils are unable to provide the
necessary investment could enable the first steps towards council-led development of this
sector to be taken. This would reduce the pressure on councils to avoid biomass as a marginal
risk project and would also reduce the reliance on local entrepreneurs to drive projects
forward and to invest time and resources in sourcing funding from disparate sources.
Government underwriting of loans (or even provision of loans) would reduce lender
uncertainty and increase the opportunities for councils to secure funding for schemes.
4.21 The project at Leicester (case study 1, Appendix B), illustrates a further unintended
financial barrier to the development of biomass (and other) projects whose funding derives
from a local authority’s housing department. We recommend amending the Housing
Revenue Accounting system to allow councils to secure additional investment for district
heating and CHP systems without being penalised in other areas of funding.
4.22 There are over 600 community-heating schemes in the UK, some of which already utilise
CHP82. The councils or organisations that own these networks should be encouraged to
incorporate biomass elements using local resources when upgrading the systems. We
recommend that as part of the government/industry forum (recommended in
paragraph 2.77) a network of renewable district heating experts should be established
to enable the transfer of knowledge and expertise from one council to another.
Transport
4.23 Traffic required by an installation is a constraint on the uptake of biomass energy. Small
rural roads or streets in urban housing developments are not suitable for large numbers of
lorry movements and the siting of a plant must take into account the need to keep to a
minimum the increased traffic caused by fuel deliveries.
4.24 Table 4.2 illustrates the different delivery requirements of different scale plants by fuel
type83. The table shows that small heating or CHP plants require relatively few deliveries.
The Leicester district heating plant, for example, will need only two deliveries per day, five
days a week and will store sufficient fuel on-site to cover weekends and holidays. Any
v www.woodfuelresource.org.uk
vi Under existing EU legislation there is a Third Party Finance Initiative (TPFI) that underwrites energy
loans under a payback scheme. This will be replaced in 2006 by the Energy Services Company (ESCO)
directive which will be easier to implement that the TPFI.
52
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
increase in road traffic resulting from the operation of the facility will be an important
factor in the planning of any new biomass project. Also, over a period when, the
Commission believes, road transport should be decreasing84 it is important to ensure that
journey distances are minimised and to seek alternative modes of fuel delivery.
Table 4.2 Deliveries required by plant size and fuel type
Plant
Truck
volume
(m3)
Deliveries
(/day)
wood chips
Deliveries
(/day)
straw bales
Deliveries
(/day)
miscanthus bales
Large scale
biomass
combustion
(30MWe)
120
21
28
17
Large scale
biomass
gasification
(30MWe)
120
17
23
13
Small scale
biomass
combustion
(5MWe)
120
5
6
4
Small scale
biomass
gasification
(500kWe)
60
1
1
1
Industrial
biomass
heat (1 MWth)
60
0.5
1
0.5
Co-firing 5%
biomass (25 MW )
120
16
22
13
Based on references above, using density values of 0.15 m3/t for wood chips (Suurs, 2002), 0.11 m3/t for
straw and 0.19 m3/t for miscanthus (Bullard, 1999)
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
53
Carbon dioxide balance
4.25 Below, we discuss the relative economic and environmental costs of different modes of
transport for the various biomass fuels. Transport will add to the CO2 costs of biomass fuels
and this must be offset against the CO2 reductions secured from use
of biomass. Table 4.3 shows CO2 equivalent emissions from a willow-fuelled
plant, supplied by willow from within a 50km radius. Road transport is assumed, and
the equivalent figures for coal and natural gas-fuelled power plants are shown
for comparison.
Table 4.3 Comparison of CO2 equivalent emissions from biomass, coal
and natural gas to electricity chains (g CO2eq/kWhe)
Biomass
Production
Transport
Conversion
Clean-up
Total
59
17
0.7
0.2
77
Coal
97
957
0.04
1054
Gas
15
396
0
411
Plant efficiencies: Biomass 32%, Coal 38%, Natural Gas 52%.
4.26 The table shows that the bulk of the emissions for biomass production occur in the
production and transportation stage and that these are very high compared to gas.
However, these emissions are more than offset by the very low conversion emissions. There
are also opportunities to reduce production and transport emissions as the biomass sector
develops; making biomass even more favourable compared to the fossil fuel alternatives.
Transportation of biomass
4.27 Transport costs remain a limiting factor in the price and financial viability of biomass as a
fuel. The loss of most of the UK’s country railways has forced farmers to resort to road
transportation for their crops. This is the most expensive mode of transport: the costs and
environmental impacts are substantially higher for road transport than for rail or ship.
These costs are illustrated in Table 4.4 in financial terms and in terms of the related
emissions.
54
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Table 4.4 Costs and emissions for transportation of biomass
Mode of
transport
Fuel Type
Transport Cost
(£/odt/km)
CO2 equivalent emissions
(kg/odt/km)
Road
SRC (chip)
0.077-0.086
0.18-0.27
Miscanthus (baled)
0.058-0.080
Forest Materials (chip)
0.077-0.086
Straw (baled)
0.102-0.139
Rail
Ship
SRC (chip)
0.040
Miscanthus (baled)
0.028
Forest Materials (chip)
0.036
Straw (baled)
0.04
0.028-0.048
SRC (chip)
0.010-0.014
Miscanthus (baled)
0.008-0.0011
Sea
Waterways
Forest Materials (chip)
0.010-0.014
0.012-0.024
0.022-0.066
Straw (baled)
0.014-0.019
4.28 These figures may seem to indicate that transportation by ship would be the most desirable
method of distributing biomass; indeed biomass is already shipped around the globe for
co-firing or for production of heat and electricity85. These costs, however, do not adequately
reflect the total costs - even shipped biomass still needs to be transported from the field to
the port and on from the port to the plant, which will require road transportation for farms
and plant not located at ports or railheads. Emissions other than CO2 from shipping are
also a matter of growing concern. The environmental impacts of shipping biomass would
therefore extend beyond the emissions data in the table above. It is also worth noting that
distances over which shipped biomass travels is significantly higher than road or rail
transport distances so the cumulative costs will be correspondingly higher.
4.29 Importing biomass reduces the incentive to UK farmers and foresters to diversify into fuel
production and has implications for security of fuel supply for the UK and for UK
agriculture and forestry. For these reasons we have not examined closely the scope for
imported wood to be a major source of fuel in the UK, but it may have a short-term role in
the development of the biomass energy sector.
4.30 Because many forestry materials and, in particular, municipal arisings already incur
transport costs, the marginal costs of their transportation to an energy facility are likely to
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
55
be zero or very low. Also, their dispersed location makes them often more suitable for
localised district heating or CHP schemes. This means that transport distances and the
associated costs (both economic and environmental), can be kept to a minimum. The
mode of transport used for municipal materials in particular is dictated by the practicalities
of collecting and distributing the materials; in an urban setting road transportation will
usually be the only option. Transport costs are therefore more of an issue for the
distribution of dedicated energy crops than forestry or municipal materials.
4.31 As all of these biomass materials have relatively low densities, transport is volume-limited,
not weight limited. As a result, the cost per tonne per kilometre varies for different
feedstocks, due to the difference in density between wood chips, straw bales and
miscanthus bales.
4.32 The use of lorries for transporting the fuel restricts the economic distances over which the
fuel can travel. Using the graphs below (4-I and 4-II) it is possible to estimate a maximum
economical transport distance for the potential biomass fuels. Using this distance it is then
possible to calculate the economically viable collection radius for the fuelvii and the crop
density that would be required within that radius to service a power station.
Figure 4-I Transport costs of biomass by distance
160
140
Cost (£/odt/km)
120
100
80
60
40
20
0
0
10
20
30
40
50
60
70
80
90
100
Distance (km)
SRC (min)
SRC (max)
Straw (min)
Straw (max)
Miscanthus
Forestry residues (min)
Forestry residues (max)
4.33 The resource density is the proportion of land within a specified area that can be used to
provide a fuel. For example, a power facility that is built near a forest will have a high
resource density. In contrast a power facility in a city will have a much lower resource
density as only small areas of the radius around the installation will be producing fuel (parks
that are interspersed between buildings and roads etc). A higher resource density implies
that fuel can be sourced closer to the plant, leading to lower transport costs and lower
impacts for an installation of a given size.
vii The average journey is 2/3 of the radius
56
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Figure 4-II Resource densities for biomass stations by collection radius.
30%
Large scale combustion (30MWe)
Large scale gasification (30MWe)
Small scale combustion (5MWe)
Small scale gasification (500kWe)
Industrial heat (1MW)
Co-firing (25MW)
Resource density
25%
20%
15%
10%
5%
0%
0
20
40
60
80
100
Radius (km)
4.34 It is likely that early ventures into energy crop production will be tightly linked to markets,
as at ARBRE or West Dean. Bauen86 has calculated mean economic road transport
distances, with maximum acceptable feedstock cost of £60, to be 33-54km for forestry
residues, 28-33km for straw, 30-60km for SRC, and 20km for miscanthus. These
correspond with collection area radii of 50-81 km for forestry residues, 42-50km for straw,
45-90km for SRC and 30km for miscanthus (paragraph 4.32). Even using road transport,
over these distances the CO2 gain over fossil fuels confirms that biomass is an attractive
renewable energy option. Further, there are few parts of the UK where there are no demands
for heat or no options for using electricity within 50 km. In most parts of the country
sources of biomass of some sort, whether energy crops, forests, straw or municipal tree
surgery, could be developed. It appears that, provided a sensitive approach to vehicle
movements in residential areas is adopted (paragraph 4.23), transport will not be a limiting
factor, especially in the early stages. However, better ways of transporting the material will
need to be adopted as the market matures in order to maximise environmental gains and to
avoid damage and nuisance. We therefore recommend that transport demands be
reviewed at each of the four stages of the development of energy crop production.
4.35 A significant obstacle to the development of crops for energy in the UK lies in the logistics
of distributing the crops to the generators and subsequently getting the energy to the
consumer. The Biomass Infrastructure Scheme, presently worth £3.5m and awaiting stateaid approval from the European Commission, is intended to help develop the supply chain
and market infrastructure for forestry materials, energy crops and straw for energy use by
bridging the current gaps between fuel-growers, generators and energy end users; it will aim
to bring the stakeholders together and make the movement of all types of biomass and
biomass energy more efficient. The Commission strongly supports the earliest possible
implementation of this scheme.
4.36 We accept that there will be areas of the UK where one or more of the limiting factors will
be present; these areas will not be suited to biomass generation. This is not a cause for
concern. As stated in chapter 1, biomass is not being proposed as the sole energy solution
for the UK (paragraph 1.15). The overall contribution from biomass will be a small but
significant and valuable proportion of UK energy generation and it should be seen as a part
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
57
of a diverse, integrated energy portfolio. We do stress however that the possibility of
biomass generation should be investigated at every opportunity to ensure that it is given
thorough consideration wherever applicable.
Energy conversion facilities
4.37 The number of facilities required to produce energy at a given rate will depend on the type
of installation, and in particular their size and efficiency. Here we consider two scenarios
based on the types of heat-only or CHP installations discussed in chapter 3:
i Small heat-only
ii Large steam-cycle CHP
iii. Small gasification/pyrolysis unit using a piston engine
iv Large gasification/pyrolysis unit using a turbine
4.38 Table 4.5 illustrates typical energy outputs of these four types of facility, showing the split
between electrical and heat output when they are used as CHP units.
Table 4.5 Energy conversion facilities
Type
Efficiency Fuel input
Output
Heat
Power Total
(MWth) (MWe) (MW)
Wood
Land use Resource
density
odt/y
hectares
%
%
(MW)
Small heat-only
75
1.3
1
0
1
4,056
406
0.2
Large steam-cycle
CHP
80
53
30
12
42
170,333
17,033
8.7
Small gasification/
pyrolysis
75
1.3
0.7
0.3
1
4,056
406
0.2
Large gasification/
pyrolysis
80
49
29
10
39
158,167
15,817
8.1
4.39 The table also shows, by way of example, the amount of wood required to fuel these plants87
and, if all that wood were to come from energy crops, the area of land needed to grow them.
Paragraph 4.34 discussed maximum economic transport distances; on that basis a
catchment area with a 50km radius around each plant is assumed, to indicate the percentage
of land within that catchment that would be needed for fuel production (Figure 4-II). The
58
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
picture would be complicated where many plants are located within the same catchment
area, which would very likely be the case with the smaller sized facilities - in this case the
percentage of land required to grow energy crops would be correspondingly higher. Where
some of the fuel comes from straw or other sources of wood the area required for energy
crops would be correspondingly lower. The total amount of land required for the
production of energy crops across the UK is discussed in paragraphs 4.44 - 4.54, but it can
be seen from the last column of table 4.5 that facilities capable of powering fairly significant
conurbations might require resource densities approaching 10% within a 50km radius.
4.40 Table 4.6 illustrates the number and size of facilities that might typically be required by the
years 2020 and 2050 to achieve 16 GW of biomass energy, the upper end of the range
proposed in the Twenty-second Report (paragraph 1.15). Scenario 1 assumes significant
investment in small facilities of around 1MW (types i and iii, for example) so that roughly
50% of the total biomass energy is from such plants. In Scenario 2 the main emphasis is on
the larger facilities of around 30 MW (types ii and iv), with only 10% of the energy coming
from smaller units. The use of biomass in large co-firing power stations would markedly
decrease the number of heat-only and CHP plants required by 2020, but this should largely
have been phased out by 2050.
Table 4.6 Numbers of generating facilities required to deliver 16 GW
Year
Scenario 1
Scenario 2
1 MW
30 MW
Total no.
of installations
1 MW
30 MW
Total no.
of installations
2020
2783
93
2875
557
167
724
2050
8000
267
8267
1600
480
2080
4.41 Table 4.6 suggests that between 200 and 500 large generation plants of the size of Enköping
(case study 3, Appendix B) or ARBRE (paragraphs 3.35-3.38) might be needed, supported by
between 1,600 and 8,000 small installations, typically of the sort that might be found powering
hospitals, universities or industrial operations; by comparison, in 2002 there were already
55,000 wood-burning facilities in Austria. There is little evidence yet of any progress towards
producing either biomass generating capacity on this scale in the UK or the fuel to power it88.
Only seven biomass power generation plants are operational in the UK at presentviii; there is
therefore a need for a programme to accelerate the introduction of more plants.
viii These are plants supported by NFFO and so they do not include heat-only plants. However, only
a small number of heat-only plants are currently operational.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
59
4.42 Three factors need to be addressed if the rate of construction of biomass conversion
facilities is to be accelerated:
• provision of financial underpinning over sensible time frames
(paragraphs 4.2 - 4.17);
• securing effective markets for the heat output from the facilities
(paragraphs 4.18 - 4.22); and
• engaging the public in the development of the sector
(paragraphs 4.64 - 4.72).
Land-take
4.43 We consider below the area of land that will be required to supply 16GW of biomass energy.
4.44 As discussed in 3.44, the calorific
value of wood is very variable,
depending in particular on its
moisture content. Consideration
of “oven dried tonnes” (odt)
overcomes this to a certain
extent but still does not take into
account the differences caused
by the loss of energy in the
latent heat of steam produced
during the combustion process
(paragraph 3.3). Uncertainties are
compounded by the large range
of conversion efficiencies, from
around 30% in an electricity-only
plant to above 80% in a CHP
facility.
Box 4A Megawatts and hectares
The combustion of a single tonne of wood
will provide a single quantity of energy,
measured in megawatt-hours (Box 1A). The
energy per unit weight is the calorific value of
the wood (paragraph 3.3).
The rate of combustion of wood (tonnes per
year) determines the rate of production of
energy, measured in megawatts. The
proportion of this energy that is useable is the
conversion efficiency of the generating plant.
The relationship between hectares and
megawatts thus depends on the yield per
hectare of the energy crop (tonnes per hectare
per year), the calorific value of the biomass
(megawatts per tonne) and the conversion
efficiency of the generating plant.
4.45 With CHP usage, very roughly, 1
tonne of wood per year will
generate on average 2 megawatthours of energy. This implies that
the lower target of 3 gigawatts of
energy from biomass, would consume wood at a rate of about 13 million tonnes per year.
For the higher target, 16 gigawatts, about 70 million tonnes of wood would be required.
4.46 If all the wood for these scenarios was derived from energy crops at an average yearly yield of
10 odt per hectare (paragraph 2.14), some 1.3 million hectares of land would have to be used
for energy crops to deliver the lower target and 7 million hectares for the higher target. To put
these numbers into context, as discussed in chapter 2, there is currently some 17 million
hectares of agricultural holding in the UK. The bulk of this land is classified as grades 3,4 and
5, and is of lower value for food production, suggesting that it could be considered for energy
60
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crops. However geographical location and ecological considerations might mean that if the
upper 16GW target is to be attained through energy crops alone, areas of grade 1 and 2
agricultural land would also have to be used. Currently less than 2 thousand hectares of
agricultural land is under energy crop cultivation (paragraph 2.40) and a major change in
land use would therefore be required to meet even the lower target.
4.47 As discussed in chapter 2, other sources of biomass could be available to reduce the amount
that needs to be produced from energy crops. These other sources may be particularly
important in allowing time for the change in land use required for the production of energy
crops as well as reducing their final land-take. Forests, sawmills and municipal tree
management could provide about 1.3 million tonnes per year this decade (Figure 2-I).
Theoretically this could rise to 10 million tonnes per year by 2020, reducing somewhat after
this. Straw could also be used, with some 21 million tonnes per year potentially available
from wheat and barley and 2.5 million tonnes from rape (paragraph 2.25).
4.48 Figure 4-III illustrates one scenario for meeting the higher energy from biomass target of 16
gigawatts, by 2050 using forestry products, agricultural wastes and energy crops. The basic
assumptions for this figure are that the calorific value of wood is 10 GJ per tonne and that the
average energy conversion efficiency is 75% (i.e. the biomass is being used in CHP facilities).
It is also assumed that the currently available wood from forests and sawmills could all
potentially be used, that this increases to half the amount theoretically available at 2020, and
that it then settles at about twice the currently available level. About one third of the straw
currently produced is also assumed to be used for biomass energy and it is presumed that this
remains constant in time. Fig.4-III shows the resulting scenario for the total amount of
energy from wood and straw each year over the period 2005-2050. The requirement for
energy crops is then estimated as the remainder. The figures on the right hand side of the
graph indicate the millions of tonnes of wood or straw required from each source by 2050ix.
Figure 4-III Scenario for 16 GW of energy from forestry, straw and
energy crops
20
Gigawatts
16
12
55 Mt
8
4
7.5 Mt
2.5 Mt
0
2005
2015
2025
Year
2035
2045
Forestry
Energy crops
Straw
GW from biomass
ix Prior to 2010, the relative contributions of forestry and straw are not defined, but given the assumptions
described above, the potential resources are more than enough to meet the requirements of the energy
scenario.
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4.49 In this scenario for moving towards 16GW from biomass, energy crops would not be
needed before 2010. The first two stages of the four-stage approach described by Bauen89
and discussed in chapter 2 (paragraph 2.41) and below would continue until 2017 at which
time forestry, straw and energy crops would provide roughly comparable inputs. After
2020, energy crops would become the dominant source.
4.50 Assuming, as before, that 1hectare of land yields 10odt of wood per year, the implied land
that would have to be under energy crop cultivation at any time is indicated by Figure 4-IV.
The land required for energy crops would rise from 1 million hectares in 2020 to 5.5 million
hectares in 2050x.
Figure 4-IV Land-take for energy crops to contribute to 16 GW Biomass
energy by 2050
6
Million hectares
5
4
3
2
1
0
2005
2015
Stage 1
Stage 2
2025
Year
Stage 3
Stage 4
2035
2045
Land required for
modest scenario
4.51 The figure provides a rough idea of overall demand for land but it does not take into
account the need for transport distances to be minimised and the importance of installing
generating facilities near markets for heat. This will, to a large extent, constrain the source of
fuel used in any particular location. In some parts of the country, forest wood will not be
available within a viable distance; if markets for biomass-generated heat are available, the
production of energy crops will then need to be stimulated. Similarly there will be other
parts of the country where straw or forest wood are the locally available fuels. It seems likely
that sufficient wood could be gathered or grown to meet the 16 GW target, but councils
with a market for biomass-produced heat wishing to stimulate its uptake as recommended
in paragraph 2.48 should assess the strengths of the various sources in their area.
4.52 At each stage it would be prudent to re-evaluate the amounts of wood available from each
source and the efficiencies of production and use, and use the economic tools discussed in
x If much more optimistic figures of 75% of availability for forest and straw, 20 GJ per tonne calorific
value, 80% generation efficiency and 15 odt per hectare yield are used, then the 1 million hectares for
energy crops would be sufficient to meet the full 2050 16 GW target.
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chapter 2 and 3 to adjust the rate of production of wood. The staged approach would also
provide an essential opportunity to track the environmental impacts of the various sources
of wood and associated combustion plants. There will be gains, such as the increase in
biodiversity expected from willow SRC (paragraph 2.33), sewage disposal opportunities
(paragraph 2.28) and, of course, the production of a renewable energy source. The potential
negative impacts that will need to be closely monitored arise from the landscape issues
discussed in chapter 2 (paragraphs 2.30 - 2.32) and the provision of water for energy crops in
areas of the country where water is not abundant.
4.53 We recommend that a strategy for increasing energy crop production must include both reassessment of fuel sources and rigorous impact monitoring, with strategic environmental
assessments, at each stage.
Planning for biomass
4.54 Government policy (and the Renewables Obligation in particular) has failed to take
account of the time that is required to establish an energy crop. Using the example of a
2,000 MW station that currently co-fires 5% of its fuel as biomass, by 2009, 25% of this
biomass proportion must be from dedicated energy crops (1.25% of total fuel); if the
generator chose to continue to fire the same proportion of biomass, this would require
30,000 odt of willow SRC. At current yields of 7 odt/ha/y over a three-year harvest cycle
(i.e. 21 odt/ha over 3 years), this means that the generator would require the willow from
around 1,500 hectares of land in 2009.
4.55 These crops would take 4 years to grow, so to be ready for harvesting by the 2009 deadline
they would need to be planted in the spring of 2005. Farmers plan their land-use ahead of
time because they need to order seeds (or cuttings for willow SRC) and prepare the land
(rabbit proof fencing can be expensive and time consuming to erect). This would need to
begin in mid-2004 for everything to be in place for a spring 2005 planting date.
4.56 Willow SRC is eligible for a Defra planting grant, which farmers need to know is guaranteed
before they order the plants and fencing. The paperwork for these grants takes around 3
months. In order to reach the 2005 planting date, applications for planting grants would
need to have been submitted no later than April 2004.
4.57 Farming co-operatives may have needed to be established to ensure that enough land was
available to produce the wood required. This could easily take 2 months or more to organise,
which means they would have had to start making arrangements in early February 2004.
4.58 Once this process has begun it would need to be repeated for at least three years to ensure a
harvest every year in the SRC cycle. This could bring a farmers’ co-operative’s total planting
area to almost 5,000 hectares, and possibly more as the energy crops percentage of co-firing
increases between 2009 and 2016. A land commitment on this scale would require
assurance from the generator that they would purchase the fuel, otherwise farmers would
not be eligible for the Defra grants that are dependent on end-user contracts and they
would not be confident to commit that area of land to a crop for an uncertain market.
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63
4.59 Farmers are therefore unable to proceed without a contract from a generator, yet the
generator is able to benefit from the Renewables Obligation system without any
commitment to a grower. The fear among growers is that generators will co-fire for as long
as they are unrestricted in their use of biomass (and can use imports) and then will stop as
soon as the energy crop requirement is introduced in 2009.
4.60 The situation is further complicated by the fact that generators are reluctant to offer
contracts to growers because they are concerned that the Large Combustion Plant Directive
(LCPD) may severely curtail the long-term future of some power stations. Until they know
how the Directive will affect them, they cannot offer a contract to a biomass supplier. If this
took too long it would be too late for the farmers to plant their coppice. Growers would
have required a contract or letter of intent by the end of January 2004 to enable them to
supply sufficient fuel to enable the generator to meet their 2009 RO deadline. As far as we
have been able to establish, this has not happened and the future of energy crops for cofiring is consequently now in doubt. Generators are likely to comply with the LCPD
through some combination of the fitting of flue gas desulphurisation (FGD) equipment,
use of low sulphur coal and adjustment of power-station load factors. It may be that the
income from ROCs gained from the use of co-firing in a number of power stations would
help the generators to fit FGD in one of them. It would then be important, if FGD power
stations had to close, for the FGD station to be able to honour all the contracts to growers
that were outstanding. We recommend that the required methods of accounting and
administration for the ROCs should ensure that this can and does occur.
4.61 The purpose of co-firing is to stimulate the energy crops market; it is currently failing to do
so. With the added security of compulsory contracts, supply of energy crops would increase
(paragraph 4.7), which in turn should encourage the uptake of biomass schemes other than
co-firing. This will only happen if, as we recommend, the restriction on materials for cofiring is combined with a requirement that the generators confirm their intention to cofire by awarding long-term contracts to growers without which they should not be able
to qualify for ROCs.
4.62 The combination of policies from different government departments and from Whitehall
and Europe are hence working against each other and causing a deadlock in the biomass
industry. We recommend that the government introduce an integrated strategy that
incorporates every part of the supply chain to support and promote a biomass energy
industry in the UK.
Public acceptability
Causes of concern
4.63 A review90 of earlier research in 1998 concluded that the widespread establishment of SRC
was potentially acceptable to most users of the countryside. However, a recent study91 has
identified that concerns were likely to be about:
• generating plant,
• storage/processing building proposals,
• associated traffic movements,
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• visual impacts,
• doubts over the reliability and location of biomass supply,
• lack of benefit for the local community.
4.64 A key problem identified in case studies was the site-specific nature of NFFO contracts.
Proposals for such contracts were based on one site, determined in a secretive process, and
not open to subsequent modification. Public consultation was then aimed at persuading
the public of the correctness of the choice, rather than being a genuine consultation. New
plans should recognise the importance of community involvement in planning decisions
and be genuinely open and flexible. It is essential that uncertainties and different premises
be explicit in the planning process. A key recommendation of the Commission’s Twentyfirst Report, Setting Environmental Standards, was that people’s values should be integrated
into each critical stage of decision-making. These principles should be applied when
planning any biomass installation. In our Twenty-third Report, Environmental Planning, we
made recommendations on improving procedures and developing new processes for more
effective and productive public involvement in the development of new schemes.
4.65 With any new-build biomass facility, as with any combustion process, there is also likely to
be public concern about emissions. At an early stage, it is necessary to ensure that the public
in general, and major players such as the environmental groups, are comfortable that
emissions will be satisfactorily controlled and that biomass generation represents a
contribution to essential developments in energy provision. Risk estimates, often
presented as the objective outcome of a scientific assessment, may involve important but
often obscure assumptions and value judgements. Thus perceptions of risk that diverge
from expert estimates are not necessarily irrational but may well reflect different values from those
underlying the expert assessments92. The conflict between the values and risk estimates of local
experts and industry experts has been cited in a number of studies93 as a source of
contention during the planning stages of biomass facilities.
4.66 The need to minimise the intrusiveness of plant by careful design and location was
discussed in chapter 3 (paragraph 3.56). In particular, for plants situated in residential areas
the ensuring ‘ownership’ of the
plant by people living near it is
essential. This suggests that small
plants serving local communities
may be better accepted than large
ones that also serve communities
living some distance from the
plant. A public perception of
biomass plants is influenced, to a
degree, by the existing situation.
Plant replacing old, inefficient,
polluting oil-fuelled plant (that are
used in many off-grid areas) are
likely to cause less concern than
plants that are planned as new
Wood chipper and storage shed surrounded by walls and trees,
installations.
West Dean
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65
4.67 Local public involvement in a scheme is important, and the developer and council will
need to:
• make explicit the local benefits and impacts from the facility,
• ensure that local energy costs are reasonable,
• ensure complete transparency throughout the process,
• demand sensitive design and architecture,
• engender not just openness but involvement.
Role for government
4.68 The acceptance of renewable energy options by the public is important to the success of any
energy strategy that reduces CO2 emissions to the levels that will stabilise climate change.
The government has an interest in engaging public opinion in the debate about renewables,
including biomass. There may therefore be a role for Government in assisting the
communication process leading to the development of individual planning proposals, to
ensure that public concerns are addressed and that renewable energy strategies are enacted.
4.69 A broad range of opinion should be incorporated into the key stages of design and planning
of biomass projects. This is important to ensure that the assessment processes properly
address public concerns and do not overlook the importance of incorporating a range of
different perspectives into the design of a scheme and its subsequent implementation. This
will require a fully transparent process, with information about biomass energy placed in
the public domain and machinery in place to obtain the views of a broad range of people.
In our Twenty-first Report we proposed a conceptual framework for environmental policy
that involved several complementary and inter-related components, including inter alia
scientific evidence, risk assessment and economic appraisal. We recognised that all
components would be characterised by uncertainty or indeterminacy, and might be
influenced by different interests and beliefs.
4.70 The Office of the Deputy Prime Minister is currently consulting on replacing existing
planning guidance on renewable energy (Planning Policy Guidance note: Renewable
Energy - PPG22). The new consultation document, Planning Policy Statement 22 (PPS22),
is much more concise than the document it is proposed to replace, and gives more guidance
on the importance of achieving renewable energy targets and how to address conflicts with
other land uses. It highlights the public concerns raised in connection with renewable
energy projects and gives advice on addressing them, whilst achieving the overall renewable
energy objectives. The guidance note remains to be finalised.
4.71 There is more that could be done centrally, however, to initiate and inform debate about
biomass energy. We recommend that the network of existing Renewable Energy Advice
Centres should be expanded to increase the level and geographical coverage of the
advice available. Performance incentives should reward those centres that see schemes
through from advice to installation and operation. Models and Internet displays of
energy crop plantations and conversion plants and demonstration projects would help.
Biomass is not a cheap form of energy; it requires high levels of capital investment and part
of this is the cost of establishing that the scheme will be acceptable to the public.
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Phased delivery
4.72 A gradual approach to the introduction of biomass energy will be needed. The four stages
recommended below will provide a framework within which this gradual approach should
include the introduction of the technology to people who might have a view on its
acceptability, the appraisal (and, from time to time, the re-appraisal) of the availability of
biomass fuel from the sources we have identified, and rigorous monitoring of the
environmental impacts of energy crops and energy generating plants.
First stage ( 2004-2012)
4.73 Bauen94 defined this period in terms of a relatively small proportion of set-aside land being
used for energy crops. Figure 4-IV indicates that this might last until 2012, but it could last
considerably longer. During this period:
• government grants for the production of biomass, the development of demonstration
conversion facilities and assisting the introduction of district heating schemes should
be rationalised;
• government should introduce the concept of energy crops to the public, gauge
reactions and ensure that public values are incorporated into future plans;
• guidance should be provided to planning authorities on sensitive design of
infrastructure, and to farmers on minimising landscape impacts and maximising
biodiversity gains;
• wood from forests, sawmills and municipal tree management will increasingly be used
as fuel, particularly in co-firing installations, to prove the system.
Second stage (2012-2018)
4.74 During the second stage the area required for energy crops increases up to an area
equivalent to the amount of set-aside land.
• Co-firing is likely to remain a major user of biomass, with increasing numbers of small
CHP plants installed in hospitals, educational establishments and
commercial/industrial premises.
• Local authorities will start to assess biomass resources in their areas and a strategic
assessment of the environmental impacts of growing energy crops will be necessary.
• This stage, which will last between 5 and 10 years, is also likely to see the start of a
significant programme of construction of larger (30 MW) biomass CHP plants near
urban conurbations.
Third stage (2018-2025)
4.75 The area required for energy crops increases significantly beyond the amount of land that is
currently set-aside. This stage might last until about 2025 with the following developments:
• a rolling programme of energy conversion facilities and heat distribution systems will
provide a gradually increasing market for wood;
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67
• farmers will gain confidence and energy crops will become an accepted main crop;
• co-firing will be phased out.
Fourth stage (2025-2050)
4.76 By this stage the programme will have been established. The farming community will be
comfortable with energy crops, district-heating schemes will be the norm in new build
residential and commercial developments and local communities will have a sense of
ownership of their local generation plant. The area of land under energy crops increases, up
to 2050, to be a significant proportion of total available agricultural land. By this time it will
be important to start examining other transport options, with increasing use of rail to
deliver wood to processing and distribution centres.
A strategic approach
4.77 This report has shown that the production of the wood, its transportation and its
conversion into energy have to be integrated if investment, efficiency and public
acceptance are to be achieved. Farmers will not grow energy crops, or foresters gather them,
unless a market in the form of energy conversion stations exists, and these will not be built
unless there is a market for the heat and electricity they produce - whether through district
heating networks or advantageous electricity prices. The public will not accept the
technology if they fear unacceptable levels of intrusion into the landscape or reductions in
air quality.
4.78 Experience has shown that the introduction of biomass renewable energy systems in the
UK will not be easy without considerable planning and a certain amount of seed-corn
investment by government. But equally, experience in other countries shows that biomass
can make a significant contribution to energy supply and that the investments are
worthwhile. In this report we have shown that economically and environmentally, biomass
energy could be viable and ought to be pursued, and we have set out a staged approach to
delivering the targets for biomass energy proposed in our Twenty-second Report.
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CHAPTER 5 - CONCLUSIONS & RECOMMENDATIONS
5.1
In 2000, the Royal Commission on Environmental Pollution published its Twenty-second
Report, Energy - The Changing Climate. The government subsequently accepted our key
recommendation of a 60% reduction in CO2 emissions by 2050 and stated in the Energy
White Paper that the UK should be put on a path towards achieving this reduction. In the
Twenty-second Report we explored a number of ways for reaching that target, and the use of
biomass as a useful source of renewable energy was a significant component of these
scenarios. In this report we have considered the use of biomass further.
5.2
Biomass energy production is close to carbon neutral and has the added advantages over
other sources of renewable energy of being controllable and of producing heat; both of
which would increase the reliability and the security of the UK’s energy supply. Biomass
energy is well established in several countries around the world - the technology is proven
and the benefits demonstrated; but so far, uptake in the UK has been extremely limited.
Conclusions
5.3
Sufficient biomass is already available to initiate the development of the sector, in the form
of forestry products and by-products, straw and municipal arisings. Systematic use of this
material will have the additional benefits of providing additional income streams for
farmers and foresters, improving forest management, and diverting materials from landfill.
In the longer term, the use of biomass for energy will depend at least partially on the
production of energy crops. This would require a significant change in agricultural land-use
by 2050, and we have recommended approaching this change gradually, through four
distinct stages that provide opportunities for periodic assessment of the environmental
impacts, the social acceptability and the economic viability of biomass utilisation.
5.4
Biomass conversion technologies are particularly adaptable; the scale, type of fuel and heat
to power output ratio can all be varied according to local supply and demand. Distributed
generation offers opportunities to engage local communities and to develop a sense of
ownership of, and responsibility for, localised energy production.
5.5
Existing government support measures for biomass energy are complex and can conflict
with each other. In this report we propose a rationalisation of government policy and
suggest ways of making policy more effective in encouraging the development of a biomass
energy infrastructure. We also make recommendations for sharing experience and expertise
between stakeholders in the biomass sector, and we describe the agronomies and
technologies that are currently either available or in development.
5.6
There is a significant gap in government energy policy regarding heat production. Using
heat instead of, or as well as, electrical energy could increase conversion efficiencies
substantially - from typically 30% to around 80%. Biomass can be a reliable, controllable
source of both heat and power and the utilisation of this additional benefit should
therefore to be central to biomass exploitation.
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69
Recommendations
5.7
We have made recommendations in this report that encompass a wide range of measures
that could be introduced to stimulate the biomass market and make a significant
contribution to climate change strategies in the UK:
Fuel production and distribution
5.8
The grant system for farmers should be dependent on farmers meeting set environmental
standards in landscape, biodiversity and water assessment when planning and planting
energy crops (paragraph 2.46). In return, the grant payments should reflect fully the
biodiversity value of these crops (paragraph 2.38). Farmers should be awarded greater
flexibility in selecting energy crops and this should not be penalised by a restrictive grants
regime (paragraph 2.18).
5.9
Farmer security needs to be improved to encourage the planting of long-term energy crops.
Requiring generators to provide long-term contracts to growers to enable them to qualify
for ROCs would provide the necessary security for farmers and would introduce equity
between key stakeholders in the ROC system (paragraph 4.61). The government may also
wish to consider offering guaranteed markets and prices to farmers to increase security until
the markets are more developed (paragraphs 4.6 - 4.7).
5.10 The Commission supports the earliest possible implementation of the Biomass
Infrastructure Scheme to improve farmer access to markets and investor confidence in the
sector (paragraph 4.35).
Technology
5.11 Biomass energy technology, like others, must comply with environmental standards.
Planning should be sensitively designed and all possible technical measures should be
utilised to reduce noise and emissions and to increase efficiency and therefore reduce
transportation of fuel. Solid wastes, fly ash in particular, will need to be disposed of
carefully and appropriately (paragraphs 3.48 - 3.57).
5.12 The focus should be on establishing the sector through the use of existing, proven
technology whilst simultaneously developing new technologies and demonstration plants.
The Bio-Energy Capital Grants Scheme should be expanded and its guidelines revised to
make clear that its main purpose is to support the installation of biomass-based combustion
equipment to bring about a large-scale expansion of heat-only and CHP generation (poweronly generation should be excluded on efficiency grounds) from biomass. We recommend
that the government underwrite the cost of at least one but preferably several schemes to
demonstrate the commercial viability of medium-scale biomass energy projects. Future
schemes should however be designed to utilise their heat output as well as electrical power
(paragraphs 3.39 - 3.41).
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Generation of energy
5.13 Possibilities for secure arrangements should be investigated whereby Ofgem can certify
blended fuels for co-firing as eligible for ROCs at sites other than the power station that is
going to use them. Review of the ROC scheme should consider the delay in energy crop
production and how this affects current deadlines (paragraphs 3.46 - 3.47).
5.14 The scope for biomass as a source of renewable heat needs further investigation. The
introduction of a green heat credit would help to raise the profile and profitability of
schemes that use biomass. It would also encourage better efficiency in energy generation
and increase the CO2 savings of the UK energy sector (paragraph 3.32).
5.15 Biomass energy should be considered positively in all new-build and retrofit projects. The
assumption should be in favour of biomass energy in all projects; construction companies
and councils should have to justify any decision not to adopt this option (paragraphs 3.24,
4.18 - 4.19).
Strategy
5.16 The planning process should be open, transparent, flexible and inclusive. Local
communities should be involved in every stage of planning a new biomass plant and local
‘ownership’ should be encouraged in all new-build projects (paragraphs 4.63 - 4.69).
5.17 A biomass forum should be established to encourage the sharing of ideas and expertise and
to provide support to early-stage projects. This forum should be open to all stakeholders
including farmers, construction companies, local councils, power generators and
environmental NGOs (paragraphs 2.77, 4.22).
5.18 The four-stage approach set out in this report allows for periodical review and reaction to
changes brought about by the development of a biomass sector (paragraphs 4.73, 4.76).
Because of the considerable uncertainties that exist in this early stage of biomass
development in the UK, a strategy for increasing energy crop production must include
both regular assessment of fuel sources and rigorous monitoring of impacts, with
assessments of environmental consequences at each stage.
5.19 We invite the government to improve measures to encourage biomass as a long-term, stable
and secure option for renewable energy. We particularly encourage the government to
conduct an investigation into the potential for green heat production and the use of policy
measures outlined in this study to make real progress towards the establishment of this
sector. The opportunities for using biomass to reach CO2 reduction targets for the UK are
significant and all biomass policy should be aimed primarily at this goal.
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71
APPENDIX A – POLICIES TO SUPPORT BIOMASS –
DESCRIPTION OF CURRENT SCHEMES
A.1
Public support for biomass may be given to the provider of the fuel or to the generator of
the energy. This could be an individual household, a single institution (such as a school or
hospital), a community comprising both households and institutions, or an industrial
estate. The energy may be in the form of heat, power, combined heat and power (CHP) or
electricity from co-firing in coal-fired power stations. The support may be applied to the
growing, processing or distribution of the fuel, to the purchase of the generation equipment
or to the flow of final energy itself.
A.2
It will be seen that current support schemes are quite complex. There is a growing network
of Renewable Energy Advice Centres (growing out of the Energy Efficiency Advice
Centres) to give advice on the renewable energy measures that can be taken and the grants
available. The commentary that follows gives some further details of the schemes.
Support for Fuel Provision
72
A.3
There are four broad types of biomass fuel: forestry materials, where the fuel is a by-product
of other forestry activities; energy crops, such as short-rotation coppice (SRC) and
miscanthus, where the crop is grown specifically for energy generation purposes;
agricultural residues, such as straw or chicken litter; and imported biomass, for use in cofiring. There is currently no support for imported biomass for co-firing although there may
be for the energy generated from it (paragraph A.14).
A.4
The Biomass Infrastructure Scheme (presently worth £3.5m and awaiting state-aid approval
from the European Commission) is intended to help develop the supply chain (and market
infrastructure) for woodfuel (forestry materials and energy crops) and straw for energy use.
The Scheme is intended to bridge the current gap between fuel-growers and energy end- users.
A.5
The Woodland Grant Scheme (WGS) is part of the England Rural Development
Programme (ERDP), in Scotland there is the Scottish Forestry Grants Scheme (SFGS). The
schemes provide grants for managing existing woodland and for planting new woodland, as
a result of which forestry material may be made available for energy use. The WGS is worth
£139 million over the seven years from 2000 to 2006. The Farm Woodland Premium
Scheme, also part of the ERDP and only available in conjunction with the WGS, provides
annual payments to farmers to compensate for agricultural income foregone as a result of
forest planting. This scheme is worth £77 million over the same seven-year period.
A.6
The Energy Crops Scheme provides grants of between £920 and £1600 per hectare
(depending on the crop and former land-use) and is worth £29m over 2000-2006, to
support the establishment of energy crops, provided that growers have a contract for the
energy end-use for their crop, and they adhere to certain conditions. In addition, grants of
up to 50% of costs are available for setting up and operating Willow SRC (not other energy
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
crops) producer groups, and to help with the purchase of planting and harvesting
machinery to be held in common for the group.
A.7
The EU Common Agricultural Policy (CAP) provides two kinds of support for energy
crops. Energy crops may be grown on set-aside land, and on non-set-aside agricultural land
they may receive a grant under the CAP of 145 per hectare (though this is reduced pro rata
if the total qualifying acreage in the EU exceeds 1.5m hectares).
Support for Generation Equipment
A.8
The Bio-Energy Capital Grants Scheme is a UK-wide scheme worth up to £66m and
provides up to 40% of the costs of generation equipment in eligible projects. Most of the
support has so far been applied to high-technology equipment (for example, gasification),
but in principle any equipment generating heat, power or CHP from biomass is eligible.
Projects using energy crops are given priority. The funding is available to public sector
organisations for capital funding of district heating schemes.
A.9
The Clear Skies Initiative is worth £10m and supports households and communities in
England, Wales and Northern Ireland in the installation of renewables technologies,
including biomass heat (also solar hot-water panels and solar PV). There is a similar Scottish
Community and Householders Initiative, worth £3.7m over three years to 2006.
A.10 Biomass-fuelled boilers are eligible under the Enhanced Capital Allowances (ECAs)
scheme, through which firms can write off 100% of the equipment costs against their
taxable profits in the first year of investment. Equipment for ‘good-quality’ CHP
(paragraphs 3.17 –3.20) is also eligible for ECAs.
A.11 The Community Energy Programme is worth £50m and supports public-sector district
heating schemes through capital grants. So far only one of thirty-two grants (which have
used £16m of the £50m available) is for a biomass scheme, but this could expand.
A.12 The Carbon Trust provides finance for carbon-reduction projects, spending £5m on
R, D&D funding in this area in 2003. It can also make equity investments in more mature
projects. Eligible projects include the generation of heat from biomass, although such
schemes have been awarded only 1% of the total fund to date.
A.13 The Community Renewables Initiative, worth £1m and funded by the Countryside
Agency, provides information and facilitation to stimulate community-based partnerships
to promote renewables.
Support of Energy Flows
A.14 Renewable electricity generation, including that from biomass (and the electricity
component from CHP) is eligible for Renewables Obligation Certificates (ROCs) and can
receive Levy Exemption Certificates (LECs) in respect of the Climate Change Levy
(paragraphs 3.17 – 3.20). ROCs and LECs are also available in respect of the biomass input
when it is co-fired in conventional power stations, in an effort to establish biomass supply
chains. This support is planned to be phased out by 2016.
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Imported
biomass
Agricultural
residues
Energy crops
Woodland Grant
Scheme and Farm
Woodland
Premium Scheme
Forestry
materials
Industrial heat
only (process and
/or space heating)
Energy Crop
Scheme
Biomass infrastructure scheme
CAP grants
Set-aside grants
Producer group
grants
Residential/
institutional
heat only
(district heating)
Domestic heat
only (single
household)
Heat
Biomass infrastructure scheme
Biomass infrastructure scheme
Policy
Type
FUEL
Enhanced capital
allowances (boilers)
Community
Renewables Initiative
Community energy
(little biomass)
Bioenergy capital
grants scheme
Clear Skies
Initiative
Policy
Co-firing
(biomass fraction)
Electricity only
generation
(e.g. ARBRE)
Power
LECs
ROCs
Renewables
Obligation
Certificates
(ROCs)
Levy Exemption
Certificates
(LECs)
Bioenergy capital
grants scheme
Policy
GENERATION
All
CHP
Enhanced capital
allowances
Community
Renewables Initiative
Community energy
(little biomass)
LECs, ROCs
(power only)
Bioenergy capital
grants scheme
Policy
Industrial estates
New residential/
Institutional
(new communities)
Existing residential/
institutional
(eg. schools, hospitals)
Individual
households
Type
DEMAND
Table A.1 Summary of policies to support biomass
APPENDIX B – CASE STUDIES
Case study 1: Leicester City Council - district heating scheme
112
Background
B.1
Leicester City Council has a long-established history of providing district heating (DH). Its
first DH system was established in 1953 and was fuelled by locally-sourced coal. The coal
pits in the area have since closed and the Council is concerned about security of energy
supply and the continued use of fossil fuels and their associated CO2 output.
B.2
The citywide community heating system utilising CHP was conceived in 1987 following a
government-funded study. The Climate Change Review in 1989 resulted in the 1990
Action Plan. This 35-year energy reduction plan set out to reduce energy use by 50% and
stipulated that harmful emission levels should be reduced in Leicester by the year 2025.
This made Leicester the first UK city council to implement a green energy strategy and it
was designated Britain’s first Environment City where a commitment was made to source
20% of its energy supply from renewable energy by 2020. The Council saw biomass for
energy as a key way of meeting this target.
Finance
B.3
The Energy Centre team at Leicester City Council have secured £5.1 million of funding
from the government’s Community Energy Programme and £2.6 million from the East
Midlands Development Agency towards the costs of phase one of the scheme (£26.1
million), and are seeking additional funding from the private sector. The total project cost
is estimated at £64 million over 8 years and they will have to seek further public sector and
European funding as well as funding from other sources.
B.4
Such a scheme has to compete with other demands on Council funds, and is disfavoured by
the way Local Authority funding is currently controlled. As part of Housing Department
spending, heating schemes fall under the Housing Revenue Accounts system which is
subject to tight restrictions and to the “additionality” rule which means that any additional
funding must be used to release funds for expenditure elsewhere. Despite this, it has proved
possible (albeit difficult) to attract external investment in Leicester because the fact that the
main investor, i.e. the Council, cannot go bankrupt makes the enterprise less risky.
Tenants
B.5
The control of the community heating systems by the energy section of the City Council
removes the responsibility for maintenance of individual heating systems away from the
housing department and housing associations where they are connected to the community
heating system. It also benefits the tenants in two key ways; the heat provision is part of the
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
75
rent payment which is VAT free; and the Council, as the heat provider, is encouraged to
upgrade the insulation of their housing stock to reduce heat demand. In effect, the Council
or an agent established by the Council acts as an Energy Service Company (ESCO).
B.6
In ‘right-to-buy’ sales of council properties fitted with community heating systems, the
owner reserves the right to change the heating system if desired. If the property remains that
of the Council or is handed to a Housing Association, tenants do not have the right to
change the heating systems. Most right-to-buy tenants opt to keep the installed biomass
heating system as it is more cost effective than installing an individual boiler and it provides
heat at a lower running cost. It also means that they can benefit from council maintenance
and upgrades at little extra cost.
Fuel
B.7
Woodchip biomass will be used in the new plant. 70% of the woodchip needed will be
obtained from forests surrounding the city and within the East Midland region. The other
30% will be collected from the city centre where 5,000 tons of municipal arisings are
generated each year and stockpiled on Council land. The plan is for local farmers to collect
the arisings and chip them for use in the biomass plant. 70% of these municipal materials
will be unsuitable for energy uses and will be composted by the farmers, the other 30% will
be delivered back to the biomass plant for fuel. This will save the council £15 a tonne in
landfill charges and will provide an income stream for farmers. The farmers involved in this
scheme will be collecting the rest of the wood from forests and woodland around
Leicestershire and within the East Midlands. It is anticipated that sufficient fuel can be
sourced within a 10-mile radius of Leicestershire, which will keep transport distances to a
minimum.
Planning
76
B.8
The proposed scheme has not received any complaints including objections to planning
issues. Building on an existing power generation site and incorporating technological best
practice to minimise emissions and plume formation have probably enhanced its
acceptability. It is anticipated that the scheme will be able to meet all clean air regulations
except possibly for nitrogen oxides, which are exacerbated by the traffic levels in the city
centre. Only virgin wood sources will be used for woodchip production and no waste or
recycled wood will be used; this avoids any possible contamination of the fuel supply and
reduces the risk of harmful emissions.
B.9
Good service roads were already in place through residential areas as the site of the biomass
facility is within the existing community heating station, which is accustomed to taking
deliveries by oil tanker and was originally designed to cope with coal lorries. The new
biomass plant will require 2 lorries per day, 5 days per week; 4 days’ worth of fuel will be
stored on site to cover operation over holiday periods. The 20 tonnes of ash produced per
annum will be collected and distributed by the farmers who supply the woodchip, to be
used for farm products such as fertiliser.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
B.10 Concerns such as disruption from road works have been minimised by initiatives such
as ‘green digs’. A bridge needed to carry the hot water pipes over a major road, for
example, will also carry a cycle path, to add benefits for the community and to reduce
disruption. Local media have been used extensively to engage the public and to
identify and address their concerns; this has been a major part of the project to raise
awareness of the benefits of a sustainable energy supply. This will be managed
throughout the project. Milestones will be set which clearly involve the media and the
local community. In the Leicester Biomass scheme the use of CCTV during the
installation of the biomass station and its future operation will allow the local schools
to utilise the sustainability elements to fit within the national curriculum and to engage
with the project. This service would also be available through a website accessible to
everyone.
Case Study 2: West Dean district heating system
Background
B.11 The West Dean heating system was installed in 1983 to heat the main West Dean College
building, it was subsequently extended to include a number of extra buildings and is in the
process of being further extended throughout the estate. Wood chippings from surplus
materials that arise from the management of the estate’s 2,000 acres of forest are used to
generate the heat.
Forest management and fuel production
B.12 The primary function of the management of the estate’s forest is to produce timber and
firewood. The material that is chipped is the low quality wood that cannot be marketed and
the thinnings from the forest management. Prior to chipping, the wood is left at the forest
edge for a year to dry to 30% moisture, therefore increasing fuel efficiency. During 2003,
1,200 tonnes of chips were required to generate 1650MW(th).
B.13 The West Dean system is economically viable because many of the production costs are
met by normal forestry activities. Very few of the processes used in producing the fuel have
been introduced specifically for this purpose.
B.14 The delivery of the wood to the chipper is combined with the return of equipment to night
storage each evening and so requires no additional journeys (although transport fuel use is
slightly higher for a loaded vehicle). Excess materials from the chipping process (bark, twigs
etc) are returned to the forest floor when the machinery is driven to the forest each morning.
The ash from the power plant is also returned to the forest floor; it is of little use as a
fertiliser but the estate sees this as an acceptable waste disposal route. The main additional
costs involved in the provision of chips for the heating system are those from loading and
unloading the wood and the chipping itself.
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77
New build, retrofitting and expansion
B.15 The main initial investment for installing a district heating system, whether new build or
retrofit, lies in the purchase of the equipment. This is made more costly by the lack of
domestic suppliers of suitable machinery. At West Dean, with the exception of the water
heating pumps, all of the equipment was imported from Sweden and Denmark; this
subsequently increases repair and maintenance costs.
B.16 The West Dean system was entirely a retrofit project to replace an old oil powered system.
The costs involved in exchanging one wet heat system for another were minimal. It was
made easier by the fact that all of the buildings being refitted belonged to the estate. It was
anticipated that problems could arise in retrofitting properties in a market system, as there
is no guarantee that consumers will always opt to remain in the district heat system and
investment may be lost.
B.17 The main expense in extending a district heating system lies in the underground piping.
West Dean has recently purchased 150m of piping for their extension plans at a cost of £29k
(this includes the engineering and installation costs). This cost would be expected to drop
as demand increased but it is nonetheless a massive capital investment cost.
Prospects for expansion
B.18 The West Dean estate and Nottingham University recently conducted a joint investigation
into the possibility of utilising the waste heat from the production plant to operate a low
level steam turbine to generate electrical power. The project was considered too costly
unless significant grants were made available to establish West Dean as a demonstration
plant. The aim was to make the generation plant self-powering but the project did not go
ahead as the capital investment required was too high.
Case study 3: Enköping - use of sewage sludge
113
B.19 To help meet a Helsinki agreement obligation to reduce nitrogen inputs to the Baltic Sea, the
energy company Ena Kraft, which is based in Enköping in Sweden, is using sewage sludge as
a fertiliser for its willow plantations. This is cheaper than usual nitrogen removal processes
and has proved so successful that the municipal council has financed additional willow
plantations and is processing sewage from private septic plants as well as municipal waste.
B.20 By using sewage to irrigate willow, the Enköping council diverts 250-300 kg nitrogen/ha/y
from surface waters and, ultimately, from the Baltic. Phosphorous and heavy metals are
similarly removed. Bottom ash from the Ena Kraft CHP plant is also added into this
fertiliser mix.
B.21 By using sewage sludge and recycling the bottom ash, Ena Kraft not only meets its air quality
and CO2 targets by using willow as a fuel in its power station and also secures other
environmental benefits not normally associated with energy production. Ena Kraft attributes
the success of this project to the co-operation of a number of stakeholders including the
municipal water and wastewater works, the power plant, the environmental conservation
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ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Total fuel
input:
350 GWh
Salix uptake
from ground:
Cd: 9,8 g/ha & year
Cu: 55
Cr: 41
Hg: 0,34
Ni: 28
Pb: 9.86
Zn: 731
120 ha
willowfield
76 ha
willowfield
Chips
Sawdust
Willow
Bark
100%
Boiler
Electrostatic
precipitator
Bottom ash
Cd: 10%
Cu: 50%
Cr: 60%
Hg: 20%
Ni: 30%
Pb: 20%
Zn: 20%
Fly ash
Cd: 90%
Cu: 50%
Cr: 40%
Hg: 80%
Ni: 70%
Pb: 80%
Zn: 80%
Cd: 0,75 g/ha & year
Cu: 194,5
Cr: 26,1
Hg: 0,33
Digested sludge
Ni: 12,9
Ash/sludge Pb: 15
Zn: 324
Waste water
mix
treatment plant
Cd: <1,1
g/ha & year
Clean water &
Cu: 183
sludge water
irrigation Cr: <13
project
Hg: <0,4
200,000
Ni: 25
3
m /year
Pb: 13
Zn: 341
Flue-gas
condenser
chimney
Figure B-I Metal cycle in Enköping CHP-plant
Condensed water
30,000 m3/year
Deposit
Clean water
River
3,8 milj. m3/year
board, the municipal council and the farmers. It is a complex system and requires planning,
discussion and effort to make it work, but once established it operates well.
Case study 4: Bristol and Avon - woodfuel for heat
114
B.22 Bristol City Council and surrounding local authorities and agencies have been developing
strategies for increasing the role of wood fuel in their area. With substantial forestry
resources and good opportunities for growing energy crops nearby, there is good potential
synergy between political aspirations and biomass fuel resources.
B.23 The Bristol City Council Sustainable City Team commissioned a detailed feasibility study
into the potential for using local biomass as a source of renewable energy for Council sites.
The study identified a number of potential sites and also assessed the potential for biomass
supply within the city.
B.24 A 700 kW biomass boiler at a social housing scheme would save about 70% of the current
gas consumption, and reduce CO2 emissions by 266 tonnes per year. At a plant nursery,
greenhouse heating currently consumes 56,000 litres of LPG and 15,000 litres of oil each
growing season. A 400kW biomass boiler could reduce this by 90% and save 68 tonnes of
CO2 emissions each year.
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79
B.25 Interest in utilising sawdust from a Council-run joinery has also led to an assessment of the
opportunity for investing in a small-scale wood pelleting system. This could produce
around 1,500 tonnes of good quality pellets a year for use in local biomass heating systems.
B.26 Two other potential sources of local biomass supply were identified. Existing resources
from council woodlands, and other municipal arisings were available, as well as residues
from tree surgeons. In the latter case, the tree surgeons were keen to contribute as long as a
central site for disposal and drying was available. Avon Community Woodland is one of the
series of Community Woodlands developed across the country, it brings together local
authorities and agencies for specific actions and co-ordination of policy. A great deal of tree
planting has taken place in the Community Woodlands over the past decade, but
commercial outlets for both thinnings and more mature trees are reducing in line with
overall poor market conditions for timber. A series of actions is underway to stimulate
markets for wood heating across the region in order to encourage additional markets for
this resource. Another source was recycled untreated wood waste such as wood chip
produced from pallets and off-cuts from timber processing (which a local waste
management contractor could supply). In total, around 960 oven-dried tonnes (odt) of fuel
per annum was identified within the Bristol area.
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Example costings
Case study 5: Biomass Heating Economic Evaluation
115
500kW(th) boiler for a school and swimming pool
Biomass Heating - Base Case
HEAT ONLY
POOL
Annual Heat Consumption
1,100,000
kWh
SCHOOL Annual Heat Consumption
1,250,000
kWh
Price of Gas
1.50
p/kWh
Wood chip
£30
£/tonne
Discount rate
6
%
Period
20
years
Variables
POOL
NPV
Cost of biomass system 1
£39,000
Cost of gas system
£15,000
Cost differential
Total Net Saving
£92,201
NPV of scheme
£68,201
£24,000
Cost per tonne of CO2 £16.32
1
Cost of heating with gas
£16,500
Cost of heating with wood
£8,462
Annual Savings on Fuel
£8,038
CO2 savings per year
209
Tonnes CO2
Net after c. 25% capital grant
POOL and SCHOOL
NPV
Cost of biomass system
£88,293
2
Cost differential
3
£196,973.84
NPV of scheme
£155,680.84
Cost per tonne of
CO2
-£17.43
£47,000
Cost of gas system 3
2
Total NPV Saving
£41,293
Cost of heating with gas
£35,250
Cost of heating with wood
£18,077
Annual Savings on Fuel
£17,173
CO2 savings per year
447
Tonnes CO2
Net after c. 25% capital grant
includes heat mains
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
81
Case study 6: Biomass CHP Economic Evaluation
116
260kW(e) and 500W(th) for a school and swimming pool
CHP- Base Case
CHP
Total electricity generated
1,260,000
kWh
Amount of wood consumed
1,077
Tonnes
Assume 30% electrical efficiency
Discount rate 6%
Variables
Amount of CO2 saved
Price of Electricity
5.20
Annuity Factor
11.46992
p/kWh
988 tonnes /year
SCHOOL and POOL
Capital Costs
NPV
Capital cost of installation
£320,000
Pipe work and linking to school
£22,000
Total
£342,000
Running Costs
O/M
£18,900
Cost of Wood Chip
£32,308
Net Costs
£51,208
Total Cost
£342,000
NPV of income
£568,476
NPV of scheme
£226,476
Cost per tonne of CO2
-£11.46
Income
Income from electricity sales
£65,520
Sales of heat
£35,250
Total Income
£100,770
Net Income
£49,562
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ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
APPENDIX C - SCOPE AND LIMITATIONS OF THE
SPECIAL REPORT
C.1 Compared to other forms of renewable energy, energy from biomass attracts little attention.
The number of projects using biomass energy in the UK is far less than that from energy
from waste or wind power. The Commission analysed the various forms of renewable
energy in its Twenty-second Report ‘Energy - The Changing Climate’. This study was
commissioned to investigate developments in biomass energy since the Twenty-second
Report, exploring the introduction of new technology and the extent to which government
energy policy has provided appropriate incentives for its introduction.
C.2 The main focus of this report has been on biomass as a source of heat and power particularly
through the use of CHP (combined heat and power) plants. Unlike most other sources of
renewable energy, biomass has the advantage that it can be stored, and therefore controlled;
it is also the source of a considerable amount of heat that, if captured and utilised, can offer
high efficiencies and significant CO2 savings.
C.3 A study of biomass was considered timely because of the recent failure of the ARBRE
project. Other countries have major programmes using biomass as a source of renewable
energy, both for heat and power, and are developing technologies and infrastructure to
enable them to do this, yet the recent Energy White Paper had few proposals in this area.
The UK is in danger of being left behind, and the collapse of ARBRE may exacerbate this.
If the government is to achieve its stated aims for the reduction of greenhouse gases and UK
industry is to keep abreast of developments in this area, the use of biomass will need further
government support. This study explored the importance of such support and possible
forms that it might take.
C.4 Concerns about the environmental consequences of growing energy crops and emissions
from biomass energy plants have been addressed and the carbon lifecycle examined, as well
as the energy balance involved in long-distance transportation of biomass for fuel. Public
concerns about the large-scale cultivation and use of energy crops, fears about impacts on
traditional farming, the landscape and air quality, have been explored and ways of
incorporating them into renewable energy policies have been suggested.
C.5 This study has addressed the wider implications for biomass schemes; for example,
biomass-fuelled plant can also play a role in waste management. CHP plants can co-fire
biomass with coal, and some agricultural wastes can be used as fuel.
C.6 The issue of waste was raised a number of times during the course of this study, particularly
with regards to sewage disposal and diverting virgin wood from landfill. These options have
been explored as components of the biomass energy process, but we have not covered
energy from waste in general. We have already addressed this issue in our Seventeenth
Report.
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
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C.7 This report was restricted to an overview of the potential for biomass energy production and
aimed to highlight the variety of options available that could be tailored to individual
situations. We have not taken a prescriptive approach and have not attempted to determine
fuel availability and technology suitability for specific areas of the UK; although we have
made recommendations that such analyses be carried out on a regional basis.
C.8 This report does not cover biofuels for transport or energy carriers such as hydrogen
produced from hydrocarbons. Fuels such as bioethanol from cereals and biodiesel from oil
seeds may have a role as fuels for surface transport but applications of woody biomass to
produce transport fuels are more speculative. Woody biomass gives a higher energy yield
per hectare than transport fuels from cereals or oil seed crops. It was therefore decided to
restrict the coverage of the report to the higher energy yield option of biomass. Biofuels are
not covered in this report as we view them as longer-term possibilities that might be
appropriate if surplus biomass or land is available once the more immediate applications for
woody biomass have been exploited.
C.9 Many fuels and technologies for energy generation can make contributions to reducing
emissions of CO2 and other greenhouse gases. We acknowledged the need for a diverse
energy portfolio in our Twenty-second Report and we urge the government to place an
emphasis on alternative energy sources and to develop policy and support mechanisms to
encourage the renewables sector. We consider biomass to be a vital, viable part of this
generation mix that offers real opportunities for UK energy, environment and agriculture.
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APPENDIX D - CONDUCT OF THE REPORT
D.1 The Commission announced the special report in August 2003 and called for evidence
from a wide range of organisations and individuals. The questions focused on: the principal
environmental benefits and disbenefits of biomass as a source of heat and power energy;
the public concerns regarding biomass energy generation, why these concerns arise and
how they can be taken account of in the future development of biomass energy generation;
the level of investment needed in order to introduce effective co-firing of biomass and fossil
fuels; the extent to which fossil fuels could be replaced by biomass, the timescale necessary
to develop a large-scale switch from fossil to bioenergy and the medium-term measures
needed to bring this about; the impacts on agriculture and the support available for
changing land use to energy crops; the proportion of biomass that could be provided by
forestry and agricultural by-products.
D.2 The initial invitation included questions on the viability of transport fuels from cereal and
oil-seed production. It was subsequently decided that this would require a report in its own
right and that it would not be covered in the course of this study.
D.3 This invitation was also placed on the Commission’s website with an invitation to respond.
Overall 30 organisations responded to the invitation. The report was drafted between
January and April 2004.
D.4 The organisations and individuals who responded to our invitation to submit evidence or
provided information on request or otherwise gave assistance are listed below. In some
cases, indicated by an asterisk* meetings were held with Commission Members or
Secretariat so that particular issues could be discussed.
Government Departments
Department for Environment, Food and Rural Affairs*
Department for Trade and Industry*
Scottish Executive Environment and Rural Affairs Department*
Other organisations
Association of Electricity Producers
Agrobransle AB, Sweden*
Bio-renewables Ltd
British Association for Biofuels and Oil
British Biogen*
British Energy
The Carbon Trust
Combined Heat and Power Association*
Confederation of UK Coal Producers
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85
Council for Nature Conservation and the Countryside
Countryside Council for Wales
Ena Kraft AB, Sweden*
Energy Advisory Associates
Energy Savings Trust
Engineering and Physical Sciences Research Council
English Nature
Environment Agency
EPRI
European Environment Agency
Federation of Swedish Farmers*
Forest Research*
Forestry Commission*
Leicester City Council*
MRETT
National Farmers’ Union*
National Society for Clean Air
Natural Environment Research Council
Nottinghamshire County Council
Ofgem*
Ofreg
Power Generation Contractors
Regen SW*
Renewable Power Association
Royal Society of Edinburgh
RWE Innogy*
Scottish Natural Heritage
Scottish Power
SEPA
Shell
Swedish Energy Agency*
Termiska Processer AB (TPS), Sweden*
Ulster Farmers’ Union
UNEP
United Utilities Plc
Individuals
Mr Syed Ahmed, CHPA*
Mrs Lena Åsheim, Lillöhus AB, Sweden*
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ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Dr Ausilio Bauen, Centre for Energy Policy and Technology, Imperial College
Mr Peter Billins, British Biogen*
Mr Stewart Boyle, Wood Energy Ltd
Professor AV Bridgwater, Bioenergy Research Group, Aston University
Dr R V Birnie, Macauley Land Use Research Institute*
Mr Rupert Burr, Roves Farm*
Sir Ben Gill, National Farmers Union*
Mr Eric Herland, Federation of Swedish Farmers*
Mr Eddie Johansson, Ena Kraft AB, Sweden*
Professor Tomas Kåberger, International Institute for Industrial Environmental Economics,
Lund University
Mr Don Lack, Leicester Energy Agency, Leicester City Council*
Dr Stig Larsson, Agrobransle AB*
Mr Anders Lewald, Swedish Energy Agency*
Mr Henrik Lundberg, Termiska Processer AB (TPS), Sweden*
Mr Peter McDonald, Fyne Homes*
Dr Helen McKay, Forestry Commission*
Mr Graham Meeks, CHPA*
Mr Gustav Melin, Agrobransle AB, Sweden*
Mr Kent Nystrom, Svebio and Aebiom, Sweden*
Erik Rensfelt, Termiska Processer AB (TPS), Sweden*
Mr Mathew Spencer, Regen SW*
Mr Ian Tubby, Forest Research*
Mr Lars Waldheim, Termiska Processer AB (TPS), Sweden*
Commissioned Studies
The following papers were commissioned in the course of the study:
An analysis of the use of biomass for energy. A. Bauen, R. Dixon, J. Howes (E4 tech (UK) Ltd),
J. Woods, Centre for Energy Policy and Technology, Imperial College London. 2004.
An analysis of the Combined Heat and Power Quality Assurance Scheme. S. Boyle, Wood Energy Ltd
March 2004.
Economics of biomass heating and power systems. S. Boyle, Wood Energy Ltd. March 2004.
Land requirements of bio-power and CHP plant. S. Boyle, Wood Energy Ltd. March 2004.
A summary of progress made on the four scenarios since the publication of the Twenty-second Report.
S. Boyle, Wood Energy Ltd. March 2004.
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87
APPENDIX E – MEMBERS OF THE COMMISSION
Sir Tom Blundell (Chair)
Sir William Dunn Professor and Head of Department of Biochemistry, University of Cambridge and
Professorial Fellow, Sidney Sussex College
Professor Roland Clift
Distinguished Professor of Environmental Technology and Director, Centre for Environmental
Strategy, University of Surrey
Professor Paul Ekins
Head, Environment Group, Policy Studies Institute
Sir Brian Follett
Chair, Teacher Training Agency
Chair, Arts and Humanities Research Board
Dr Ian Graham-Bryce
President, Scottish Association for Marine Science
Professor Stephen Holgate
Medical Research Council Clinical Professor of Immunopharmacology, University of Southampton
Professor Brian Hoskins
Royal Society Research Professor and Professor of Meteorology, University of Reading
Professor Jeffrey Jowell QC
Professor of Public Law, University College London
Dr Susan Owens
Reader in Environment and Policy, University of Cambridge, Department of Geography, and Fellow
of Newnham College
Professor Jane Plant
Chief Scientist, British Geological Survey (Natural Environment Research Council)
Professor Steve Rayner
James Martin Professor of Science and Civilization, Saïd Business School, Oxford University
Mr John Speirs
Chairman, Chemistry Leadership Council’s Futures Group
Professor Janet Sprent
Emeritus Professor of Plant Biology, University of Dundee
Board Member, Scottish Natural Heritage
Secretariat
Secretary
Tom Eddy
(Mr Eddy took over from Dr Peter Hinchcliffe
who retired end of March 2004)
Assistant Secretaries
Georgina Burney
Diana Wilkins
Policy Analysts
Rhian Enright
Andy Deacon
Jonny Wentworth
88
Information Manager
Guy Mawhinney
Office Manager
Rosemary Ferguson
Administrative Officers
Baaba Davis
Geoff Ofodile
Personal Secretary to the Chairman and
Mr Eddy
Dot Watson
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
APPENDIX F – REPORTS BY THE ROYAL COMMISSION
ON ENVIRONMENTAL POLLUTION
24th report
Chemicals in Products – Safeguarding the Environment
and Human Health
Cm 5827, June 2003
Special report
The Environmental Effects of Civil Aircraft in Flight
23rd report
Environmental Planning
Cm 5459, March 2002
22nd report
Energy – the Changing Climate
Cm 4749, June 2000
21st report
Setting Environmental Standards
Cm 4053, October 1998
20th report
Transport and the Environment
–Developments since 1994
Cm 3752, September 1997
19th report
Sustainable Use of Soil
Cm 3165, February 1996
18th report
Transport and the Environment
Cm 2674, October 1994
17th report
Incineration of Waste
Cm 2181, May 1993
16th report
Freshwater Quality
Cm 1966, June 1992
15th report
Emissions from Heavy Duty Diesel Vehicles
Cm 1631, September 1991
14th report
GENHAZ
A system for the critical appraisal of proposals
to release genetically modified organisms into
the environment
Cm 1557, June 1991
13th report
The Release of Genetically Engineered
Organisms to the Environment
Cm 720, July 1989
12th report
Best Practicable Environmental Option
Cm 310, February 1988
11th report
Managing Waste: The Duty of Care
Cmnd 9675, December 1985
10th report
Tackling Pollution – Experience and Prospects
Cmnd 9149, February 1984
9th report
Lead in the Environment
Cmnd 8852, April 1983
8th report
Oil Pollution of the Sea
Cmnd 8358, October 1981
7th report
Agriculture and Pollution
Cmnd 7644, September 1979
6th report
Nuclear Power and the Environment
Cmnd 6618, September 1976
5th report
Air Pollution Control: An Integrated Approach
Cmnd 6371, January 1976
4th report
Pollution Control: Progress and Problems
Cmnd 5780, December 1974
3rd report
Pollution in Some British Estuaries and Coastal
Waters
Cmnd 5054, September 1972
2nd report
Three Issues in Industrial Pollution
Cmnd 4894, March 1972
First Report
Cmnd 4585, February 1971
ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
89
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Forestry Commission (2003). Forestry Facts and Figures
Personal communication, H. Mackay, Forestry Commission, November 2003.
Twenty-third Report.
SEERAD (2003). Scottish Forestry Grants Scheme.
Personal Communication, T. Kåberger, April 2004.
ENDS (2003). Issue 342. Co-firing plans in the spotlight over biomass imports.
Forestry Commission (2003). Forests, Carbon and Climate Change: the UK Contribution.
Building Research Establishment CHP report.
D. Kidney, Balcas (2004), presentation at Forestry Commission website launch. CHP and wood
pellets production.
CHPA (2003). Submission to RCEP.
H. McKay (2003). Woodfuel Resource in Britain.
Personal communication, R. Cotton, Wood Energy Ltd, March 2004.
Council Directive 1999/31/EC on the landfill of waste.
Personal communication, N. Monether, Nottinghamshire County Council, March 2004.
EU Directive 75/442/EEC(as amended) on waste framework.
Statutory Instrument (2002) No. 2980. The Waste Incineration (England and Wales) Regulations 2002.
Sinclair and Löfstedt, Biomass and Bioenergy 21 (2001) 177-184. The influence of trust in a biomass
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ROYAL COMMISSION ON ENVIRONMENTAL P OLLUTION – BIOMASS AS A RENEWABLE ENERGY SOURCE
Image titles and credits
Front cover
Poplar & willow fuelwood plantation in Avon, copyright 1997 – 2002
Science Photo Library.
Bales of straw, copyright 1997 – 2002 Science Photo Library.
View of coppiced woodland in Norfolk, England, copyright 1997 – 2002
Science Photo Library.
Forest worker uses chainsaw to clear storm damage, copyright 1997 – 2002
Science Photo Library.
Tractor harvesting coppiced willow, Forest Research (2004).
Chipper and storage shed, West Dean P. R. Hinchcliffe (2003).
Page 11
Coppiced poplar wood chips in farmer’s hands, copyright 1997 – 2002
Science Photo Library.
Page 26
Forestry workers feed cut branches into shredder, copyright 1997 – 2002
Science Photo Library.
Page 32
Chipper and storage shed, P. R. Hinchcliffe (2003).
Page 65
Wood chipper and storage shed surrounded by walls and trees, West Dean
P. R. Hinchcliffe (2003).
The Royal Commission on Environmental Pollution is an independent body,
appointed by the Queen and funded by the government, which publishes
in-depth reports on what it identifies as the crucial environmental issues
facing the UK and the world.
Information on the Commission’s work can be found at www.rcep.org.uk.
Copies of this report are available to download from the website,
alternatively, the Commission can be contacted at:
Royal Commission on Environmental Pollution
5 - 8 The Sanctuary
Westminster
London SW1P 3JS
Email: [email protected]
ISBN 0-9544186-1-1
Published by the Royal Commission on Environmental Pollution
© Crown Copyright 2004
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