19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
FOREST BIOMASS RESOURCES FOR INDUSTRIAL ENERGY CONVERSION IN PORTUGAL
Monteiro, C.a, Tarelho, L. a, Lopes, M. a, Monteiro, A. a, Machado, L. b, Amaral, J. b, Borrego, C a.
CESAM & Department of Environment and Planning, University of Aveiro, 3810-193 Aveiro, Portugal
b
RAIZ Research Institute of Forest and Paper, 3801-501 Aveiro, Portugal
Corresponding author: C. Monteiro, e-mail: [email protected], Tel: +351 234370220, Fax: +351 234370309
a
ABSTRACT: In recent years, pressures on global environment and energy security have led to an increasing demand
on renewable energy sources, and diversification of world’s energy supply. Among these resources the biomass could
exert an important role, since it is considered a renewable and CO2 neutral energy resource, and can potentially
provide energy for heat, power and transport fuels. The option for biomass to energy has to be sustainable, that is, the
level of biomass consumption should not be higher than the level of natural production capacity of ecosystems. In this
sense, it is important that appropriate studies of biomass availability and sustainability support strategies of biomass
to energy. However, little is known about the availability of the amount of biomass in Portugal. In this scope, and
considering the need to have information about this scenario of biomass to energy, and its implications on the
Portuguese climate policy, it was initiated a study in order to characterize and quantify the biomass available from the
Portuguese forest to energy purposes. The results showed that the existing residual forest biomass estimated is
enough to feed the existing and planned thermal power plants in Portugal.
Keywords: Biomass, forest, resources, energy.
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biofuels[3].
Amongst renewable resources paramount importance
has been given to the bioenergy because it has low
negative environmental impact in terms of CO2 emissions
for the entire fuel cycle and zero CO2 emissons from
fossil fuels during operation. Since according to the EU
White Paper [4], biomass energy is versatile, because it
can be used to produce electricity, heat or as fuel for
transport as required and, unlike electricity, can be stored
in a simple and usually economically. Moreover, the
production can vary from small scale up to several MW.
The strongest incentive of EU towards development
of biomass energy was given in 2005 with the Biomass
Action Plan [5]. In this plan, the EU stated that the
increased use of renewable energy is essential for
environmental and competitiveness reasons, and
recognized that: “biomass has many advantages over
conventional energy sources, as well as over some other
renewable energies, in particular, relatively low costs,
less dependence on shorterm weather changes, promotion
of regional economic structures and provision of
alternative sources of income for farmers” [5].
The Portuguese government defined a strategy of
biomass to energy in 2006, with the launch of a program
with the objective of increase the national capacity of
electricity production from biomass. This program
included the achievement of an installed capacity of 250
MWe by 2010, and the construction of fifteen new
thermal power plants (corresponding to an installed
capacity of 100 MWe). The new power plants location
were define by the Portuguese government with the
double objective of increasing the quota of renewable
energy in the global production of electricity and to
promote the development of forest residues harvesting.
This will also serve to remove shrub competition on
forest groves and reduce wildfire hazard [6]. The Figure
1 presents the distribution of planned thermal power
plants in Portugal and their respective power production
(MVA), using GIS tools [7].
INTRODUCTION
Emissions of greenhouse gases have grown with
industrialization, and particularly from the burning of
fossil fuels, such as coal and petroleum to power
industry, to heat, cool and transport. After fossil fuels
combustion, deforestation is the second largest source of
carbon dioxide emissions into the atmosphere [1].
In the last few years some international agreements,
like Kyoto Protocol, have been written up in order to
reduce the atmospheric emissions of gases that are
thought to contribute to global warming.
In relation to carbon dioxide emissions, the forest has
a double importance: firstly, they are considered a major
sink for atmospheric carbon dioxide [2], and secondly the
energy use of residual forest biomass would reduce
additional emissions of CO2 from fossil fuels
combustions.
Since 1990, the EU has been engaged in an ambitious
and successful plan to become a world leader in
renewable energy production and use. The strategic
energy plans and policies of the EU, as well as those
individual member states, established concrete targets for
exploitation of indigenous renewable energy sources
(RES), and for bioenergy in particular.
In December 2008 an extensive package of measures,
referred Package "Energy-Climate" (or Packet 20-20-20)
as adopted, which aims to reduce GHG emissions by
20% compared to 1990, to reduce the energy
consumption by 20% through increased efficiency, and a
20% share of renewable in gross final energy
consumption of up to 2020. This policy package also sets
a target quota of energy from renewable in gross final
consumption of energy for Portugal of 31% by 2020.
Further stipulates that each Member State must
ensure a quota of at least 10% energy from renewable in
final energy consumption in transport in which the
contribution of biofuels from wastes, residues, non-food
cellulosic material and wood-cellulosic material is
considered to be twice the contribution of other
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19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
Figure 3 - Distribution of forest stands in Portugal [8].
Figure 1 - Distribution of planned thermal power plants
in Portugal [7].
The option for biomass to energy has to be
sustainable, that is, the level of biomass consumption
should not be higher than the level of natural production
capacity of ecosystems. In this sense, it is important that
appropriate studies of biomass availability and
sustainability support policies of biomass to energy [9].
At the moment little is known about the availability
of a sufficient amount of biomass in Portugal to supply
the existing industries that consume biomass intensively
(power plants, pulp and paper industries and furniture
industries) plus the new thermal power plants to be
constructed. Considering the need to have information
about this scenario of biomass to energy, and its
implications on the Portuguese climate policy, it was
initiated a study in order to characterize and quantify the
biomass available from the Portuguese forest to energy
purposes.
After this concurrence only two plants (Belmonte and
Palser) are in operation [7]. Actually there are nine
thermal power plants and nine cogeneration plants
corresponding to an installed capacity of 210MVA.
Portugal, given the location and natural resources of
its territory, is a country with potential for the exploration
of renewable energy sources. Portuguese land is wellsuited for forest growth and have a small amount of
suitable soils for agriculture. In Portugal forests cover
approximately 3.4 million hectares and represents 38% of
the national territory (Figure 2, Figure 3) [8].
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METHODOLOGY
In this scope, and considering the need to have
information about this scenario of biomass to energy, and
its implications on the Portuguese climate policy, it was
initiated a study in order to characterize and quantify the
biomass available from the Portuguese forest to energy
purposes. To proceed to such characterization, and in
result of the lack of a systematized base of information
dedicated to this issue, it was decided to initiate the work
based on the National Forest Inventory (NFI) from 20052006 [8]. The NFI contains information about the
distribution of forest species by area, densities and age
classes, among other data. Based on that information, and
using GIS tools it was determined the following
information for five tree species (Eucalyptus globulus,
Pinus pinaster, Pinus pinea, Quercus ilex, Quercus
suber), considered most suitable for energy conversion:
Figure 2 - Areas by land use in Portugal (103 ha) [8].
The main tree species which are widely planted for
commercial purposes and capable for of providing a
regular supply to meet fuel demand are Eucalyptus
globulus, Pinus pinaster, Pinus pinea, Quercus ilex,
Quercus suber.
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19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
for each class of age in Portugal with interest for
lumbering. Eucalyptus and pine stand occur mainly in the
north and center of Portugal. The other species stands
occur mainly in south and inland of Portugal.
The biomass distribution in Portugal was compared
with the actual and planned location of the main intensive
of industrial biomass consumers in Portugal (power
plants, and co-generations plants) (Figure 5).
Comparing the spatial distribution of Eucalyptus
globulus and Pinus pinaster (Figure 6 (a), (d)) it seems
that the existing and the predicted location for power
plants is suitable, because they are near regions with high
potential availability of biomass fuel. However, in
relation to the other species considered as Quercus ilex,
Quercus suber and Pinus pinea (Figure 6 (b), (c), (e)),
their main areas of production are located in regions
where no power plants implementation was planned.
i) – the spatial distribution of forest in Portugal by
species of trees and respective age classes;
ii) – the characteristics of stands of different species;
iii) – the existing forest resources on the mainland.
For tree species it was estimated the number of trees
for the class of age with interest for lumbering, their
spatial distribution in Portugal (using GIS tools) and the
existed biomass forest residues (BFR) produced in result
of sylviculture practices. The BFR amount was compared
with the estimated amount of biomass to be consumed in
existing and planned thermal power plants.
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RESULTS AND DISCUSSION
To calculate BFR it was necessary to identify and
classify forest cover, as well as to characterize forest
stand structure in Portugal.
3.1 Number of tree species of Portuguese forest
Based on typical sylviculture practices for each kind
of species considered, namely the rotation periods for
Eucalyptus and Pinus, and the maintenance cuttings of
Quercus, was estimated the number of trees for the class
of age with interest for lumbering.
The number of Eucalyptus globulus aged between 8
and 12 years old was estimated in 66 million of trees.
Pinus pinaster and Pinus pinea are both estimated in 17
million of tree, aged between 40 and 45 years old. For
Quercus ilex and Quercus suber with around 9 years old
were estimated around 680 thousand of trees (Figure 4).
Figure 4 – Number of trees based on IFN for the class of
age with interest for lumbering.
3.2 Spatial distribution of forest biomass in Portugal
After the number of trees for each class of age in
Portugal was calculated, their spatial distribution was
mapped using GIS tool (Figure 6).
The spatial distribution of forested land cover was made
at regional level, using so-called NUT II (Nomenclature
of Territorial Units for Statistics) boundaries.
The data provided by forest inventories [8] didn’t
include the sample plot coordinates, and because no
accurate map existed of forest land cover distribution
using real data. In this way, the resultant map assuming
that the forest biomass is uniformly distributed all over
the region
Figure 6 presents the distribution of the number of trees
Figure 5 - Distribution of existing and planned thermal
power plants in Portugal [7].
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19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
Eucalyptus globulus
Quercus ilex
(a)
(b)
Pinus pinaster
Quercus suber
(c)
Pinus pinea
(d)
(e)
Figure 6 – Distribution of the number of trees for each class of age in Portugal. (a) Eucalyptus globulus (b) Quercus ilex (c)
Quercus suber (d) Pinus pinaster (e) Pinus pinea.
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19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
3.3 Biomass Consumption in Portugal
Actually there are nine thermal power plants and nine
cogeneration plants in operation in Portugal
corresponding to an installed capacity of 210MVA.
There are thirteen thermal power plants planned
corresponding to an installed capacity of 95 MVA.
Figure 7 presents the biomass consumption for
existing and planned thermal power plants in Portugal.
The existing thermal power plants need an estimated
amount of 1,38x106 ton(dry)biomass/year, and the new
thermal power plants will need an estimated amount of
6,89x105 ton(dry)biomass/year, that is, a total amount of
2,07x106 ton(dry)biomass/year.
Figure 7 - Biomass consumption for existing and planned thermal power plants in Portugal.
Based on information about sylviculture practices and
lumbering numeric models, it was estimated the
following amounts of BFR for the five tree species
considered (Tabel 1): i) 4.48×106 ton (dry)/year for
Eucalyptus globulus, ii) 4.45×104 ton (dry)/year for both
Pinus pinaster (4.38×104 ton (dry)/year) and Pinus pinea
(6.82×102 ton (dry)/year), and iii) 1.21×104 ton (dry)/year
for Quercus ilex and 1.35×104 ton (dry)/year for Quercus
suber. The Figure 8 compares the biomass consumption
for existing and planned thermal power plants in Portugal
and the existing biomass from Portuguese forest.
3.4 The amounts of BFR in Portugal
In order to obtain BFR estimations, the usual
methods proposed in literature use different independent
variables such as tree diameter at breast height (DBH),
basal area, height, circumference or combinations of all
of them. The most common procedure for estimating
BFR in forest is to use allometric regression equations
based on DBH and individual tree BFR [10]. The DBH is
the most commonly used parameter because of the
precision with it can be calculated and because it is
related to the volume of the wood and the age of the tree
[11].
Table I – Number of trees and the amount of biomass (kg (dry)) obtained for different species.
Specie
Equation(c)
mfinal
DBH (cm)
T (years)
m (kg/tree)
Ntree
(ton/year)
Eucalyptus
2.194
2.645DBH
2
12,5
(a)
10
(a)
674,6
66363629
4,48E+06
Pinus pinaster
0.4684DBH 6.3722DBH+36.698
21,1(a)
43(a)
110,8
16995737
4,38E+04
Pinus pinea
0.1129DBH2.4241
21,1(a)
43(a)
Quercus ilex
2.4727
(b)
Quercus suber
0.1006DBH
2.6079
0.0343DBH
46,2
28
(b)
183,2
160180
6,82E+02
9
(a)
1314,5
83178
1,21E+04
9
(a)
203,9
594839
1,35E+04
(a) Average value for sylviculture practices [12].
(b) Values obtained by statistical analysis of data from an experimental campaign [13].
(c) Equation for determinate the biomass for each species [14].
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19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
Figure 8 - Biomass consumption for existing and planned thermal power plants in Portugal and the existing biomass from
Portuguese forest.
[2]
The analyses of Figure 8 it is verified that the total
consumption of both thermal power plants is 2,07x106
ton (dry)biomass/year and from Portuguese forest it’s
possible obtain 4,55x106 ton(dry)biomass/year.
[3]
[4]
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CONCLUSIONS
[5]
Considering that existing thermal power plants need
an estimated amount of 1,38x106 ton(dry)biomass/year,
and the new thermal power plants will need an estimated
amount of 6,89x105 ton(dry)biomass/year, that is, a total
amount of 2,07x106 ton(dry)biomass/year, it can be
concluded that the existing residual forest biomass
estimated from this five tree species (4,55x106
ton(dry)biomass/year) is enough to feed the existing and
future thermal power plants. For the tree species
considered it can be concluded that the major amount of
existing biomass with potential for exploration is
associated to Pinus pinaster and Eucalyptus globulus.
However, only a part of this estimated amount could be
made available forest biomass is accessible for
lumbering, either in result of distances for forest
production location to the industrial energy conversion
installations and several logistic issues.
Portugal has a high biomass potential which can be
used in energy production, although it is already used by
pulp and paper industries and furniture industries. Thus
the use and probable competition for the same biomass
resource requires special concern, to avoid the excess of
exploitation, and consequent disequilibrium of
ecosystems.
The potential use of biomass for energy in Portugal
has a tendency to increase, however we can’t forget that
is necessary to invest in the management and
sustainability of Portuguese forest.
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
5
[1]
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19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany
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ACKNOWLEDGEMENTS
The authors acknowledge to the Portuguese
‘Ministério da Ciência, da Tecnologia e do Ensino
Superior’ for the financing of BIOGAIR project “Impacts
of Biomass energetic recovery chain on air quality and
Portuguese
climatic
policy”
(PTDC/AACAMB/103866/2008)
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