Applied Mechanics and Materials Vol. 309 (2013) pp 206-212
Online available since 2013/Feb/13 at www.scientific.net
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.309.206
Aspects of Logistics in Biomass Supply for Energy Production
Sebastian Kot 1, a, Beata Ślusarczyk 1, b
1
Czestochowa University of Technology, Management Faculty, ul. Dabrowskiego 69, 42-201
Czestochowa, Poland
a
[email protected], b [email protected]
Keywords: biomass energy production, logistics supply.
Abstract. Energy production from biomass is now a very popular trend in energy generation. These
initiatives are supported by the European Union legislation and state governments. Undoubtedly,
the idea of renewable energy production can be justified and promising. However, it should be
considered from a wider perspective of supply chain than merely focusing on the share of
renewable sources in total energy production. The economic and ecological importance of biomass
use to energy generation largely depends on the logistics of biomass supply to power plants. The
location of biomass sources and the organization of supply are very important stages that impact on
final economic results of energy production. Furthermore, the improper choice of means of
transport and process organization for managing renewable sources of energy might have a negative
ecological effect. Therefore, the authors attempted to analyze the cost-related aspects of biomass
supply (including the seasonal biomass price fluctuation) to the analyzed power plant and the effect
of this factor on financial results of energy production.
Introduction
There has been a growing concern over energy safety in contemporary world. The emphasis has
been also on the aspects of environmental protection. Conventional sources of energy contribute to
substantial environmental pollution. Therefore, recent years has seen a number of commitments
made by the states in order to reduce the adverse effect of manufacturing processes on the
environment. This is expected to be achieved by the increased use of renewable sources of energy.
One of these sources with particular prospects for development is biomass. The use of biomass,
however, involves a series of specific requirements that must be met by the entities that search
energy and can be the reason for many problems that arise, especially in logistics.
Renewable sources of energy are the sources based on solar radiation, geothermal, wind, water and
biomass energies or the energies generated from waste processing. These sources are virtually
inexhaustible and exist everywhere in the world, yet unevenly distributed. One indisputable
advantage of renewable resources is their insignificant impact on the environment and substantial
dissipation, which to some extent solves the problem of energy transport [8].
Biomass used for energy purposes appears in free forms: waste wood from forestry and wood
industry, straw from agriculture and plants from special energy plant [5]
Energy contained in biomass can be used by means of a variety of methods which include in
particular: direct firing or co-firing by means of conventional energy sources, gasification and
fermentation of biomass to obtain biogas which is then fired, production of biofuels from oilseed
crops or alcohol. Biomass co-firing with traditional energy sources can occur either directly
(without biomass conversion) or indirectly (biomass is converted into gaseous form) and parallel
(biomass and conventional energy carrier are fired separately, but their energy is then converted
into electricity) [7].
It is estimated that the potential of solid biomass in Poland amounts to over 30 million Mg per year,
of which over 20 million is waste straw, 4 million is wood waste and 6 million is sewage sludge
from cellulose industry. These reports did not take into consideration the potential of energy crops,
which are increasing every year. As results from a study prepared by the Institute for Renewable
Energy, technological energy potential of the discussed types of biomass will have reached ca. 690
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TJ by 2020. The economic potential is expected to rise to the level of ca. 520 TJ, whereas the
market potential that represents actual opportunities for the use of these resources will be reach ca.
360 TJ [6]
The use of biomass for electricity production in Poland indicates that this source is among the most
remarkable sources of renewable energy sources (Table 1).
Table 1. Electricity produced using individual renewable sources of energy in 2005-2010 [GWh]
Source
Water
Power
Plants
Biomass
Biogas
Wind
Power
Plants
Total
2005
2006
2007
2008
2009
2010
2,176
2,030
2,253
2,153
2,376
2,922
1,345
105
1,818
117
2,343
162
3,313
221
4,888
295
5,788
363
135
257
472
806
1,045
1,822
3,761
4,222
5,230
6,493
8,604
10,895
Although the highest contribution in the period studied was observed for water energy sector
(57.2%), the leading position since 2008 has been taken by biomass energy. The most noticeable
increase in the amount of energy generated occurred for biomass and wind energy.
It should be emphasized that the biomass, which is a renewable energy source, has great prospects
for development. One group of biomass is solid biomass, which can be further subdivided. This
source is economical and can be obtained from both energy crops and waste from forestry and
agriculture, which does not generate additional costs. The major inconvenience of using biomass is
low calorific value per volume unit and can be compensated by the processes of pelletizing,
briquetting or baling. However, another substantial problem is development of the effective logistic
system of logistic supply of biomass for power plants in consideration of the problems of
warehousing and transport.
Apart from the negative aspects of warehousing and maintaining inventory (capital lock-up,
material handling or insurance) known for other goods, the biomass, during the warehousing
process can be biodegraded, which results in the deterioration of energy properties (thus they are
loss-related properties) and might lead to the growth of the mould or spore which are dangerous for
human health. Solid biofuels are also characterized by a relatively high risk of spontaneous
combustion or ignition from a small spark, which forces warehouse owners to use more advanced
fire-fighting systems. The method of storage depends on the type of biomass. Grain, forest chips or
granules are stored in silos. Straw bales are stored under the shelters, in piles and the wood logs
need to be protected from rain and require sufficient air flow. Regardless of the biomass type, if it is
stored in big warehouses, biomass needs to be frequently handled in the warehouse [2].
Analysis of the problems of transport of the biomass obtained from power plants for energy
purposes in Poland reveals that the most popular means of transport is by rail and road transport.
The transport by rail uses eight-wheel coal wagons with capacity of 69 cubic metres. Depending on
the type of biomass, the wagons are capable of transporting from 30 to 40 Mg of this fuel. In road
transport, the specific means of transport is determined by the distance to be covered by the biomass
being transported. In long-distance transport, the heavy good vehicles are usually employed (with
load capacity from 24 to 28 Mg) and capacity of 30-90m3), whereas light goods vehicles (with load
capacity of 7 to 16 Mg) are used for the distances of up to 100 km. Large vehicles used to transport
biomass are usually equipped in tipper devices, which considerably facilitate unloading.
Furthermore, the vehicles should ensure that the transported cargo is protected from humidity, both
during transport and at the stage of loading and unloading [1].
Analysis of Logistics Problems of Biomass Supply in Selected Energy Power Plant
The enterprise analysed in the study belongs to a medium-sized heat and electricity supplier with
four steam boilers and two turbo assemblies for production of electricity. Similar to other entities of
similar type in Poland, a number of investments projects were implemented in the enterprise in
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2010-2011, which allowed for generation of green energy through biomass firing. This allowed for
reduction in emissions of carbon and sulphur dioxides, nitrogen oxide and dust. The choice of the
research subject for the analysis will allow for determination of logistics problems of biomass
supply, typical of similar entities that are starting to introduce renewable sources of energy for
generation of heat power and electricity.
In the period of the study (from July to December 2011), the enterprise used biomass from
agriculture and forestry for electricity generation. Consumption of both types of biomass for
production of electricity is presented in Table 2.
Table 2 Consumption of biomass for production of energy in each month
Consumption of Biomass [Mg]
Agricultural
Forestry Biomass Biomass in Total
Biomass
July
1,164.26
2,169.36
3,333.62
August
1,152.67
1,063.65
2,216.32
September
1,084.31
1,568.90
2,653.21
October
1,408.49
1,475.81
2,884.30
November
1,346.77
1,706.23
3,053.00
December
1,712.86
2,159.23
3,871.91
Total
7,869.36
10,143.18
18,012.54
It should be noted that the changes in the level of biomass consumption were closely related to the
demand for heat power and electricity. Therefore, a substantial decline can be observed in August,
when production downtime due to reduced demands was 13 days in total. Furthermore, the
proportions of the use of individual types of biomass are largely determined by legal regulations
that define the share of biomass of agricultural origin in the overall structure of biomass used for
energy purposes cannot be lower than 40%. Therefore, excessively low share of agricultural
biomass in July had to be compensated for by a considerable increase in August.
In the period studied, the enterprise purchased biomass from 20 suppliers throughout Poland,
whereas five of them were contractual suppliers who cooperated based on long-term contracts (2
years), whereas others were spot suppliers found in the free market. The suppliers of both categories
cooperate with the analysed enterprise on different basis. Contract suppliers deliver a biomass
according to a pre-defined schedule, at a particular price. On the other hand, spot contractors do not
have a particular schedule. Each delivery necessitates separate orders. High price fluctuations might
be observed in this case.
The suppliers that deliver goods for the enterprise studied are from different regions of Poland.
There are several local enterprises among them. However, some suppliers have headquarters at the
distance of over 400 km (Table 3). This causes a substantial difference in transport costs from
different suppliers.
Supplier
Supplier 1
Supplier 2
Supplier 3
Supplier 4
Supplier 5
Spot suppliers
Table 3 Biomass suppliers
Type
of
Distance [km]
Cooperation
contractual
153
contractual
180
contractual
2
contractual
162
contractual
40
spot
46 - 472
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When purchasing the biomass, the enterprise negotiates the price including delivery costs.
However, it should be noted that this remote supply sources have substantial effect on the material
price. The deliveries from such remote locations suggest problems with satisfying the demand by
deliveries from closer suppliers.
Table 4. Volume of deliveries from contractual suppliers vs. spot suppliers
Volume of deliveries [Mg]
Spot
Sup. 1
Sup. 2
Sup. 3
Sup. 4
Sup. 5
Sup.
July
498.16
142.02
150.08
869.32
58.50
1,936.14
August
284.58
423.42
23.56
305.14
112.34
338.78
September
338.40
166.28
95.30
866.70
328.02
1,650.28
October
398.78
242.96
42.04
1,111.06
377.20
674.44
November
703.68
269.90
25.32
726.02
304.72
818.14
December
728.80
294.66
47.86
1,600.75
300.58
783.86
Total
2,952.40
1,539.24
384.16
5,478.99
1,418.36
6,201.64
The contractual suppliers have 47% to 77% share in the total of biomass deliveries in individual
months. The highest share of these suppliers was observed in August, when the demand for energy
caused the need for purchasing energy in the free market.
The data contained in Table 4 show that spot suppliers covered the highest part of deliveries in July
and September: their share in the volume of deliveries in total was around 50%. Among the
contractual suppliers, the major supplier is the Supplier 4, with the highest share in the total
structure of deliveries. The volume of biomass purchased from the Supplier 2 ranges from less than
4% of share in the total structure of deliveries in July to over 28% in August. High instability of the
volume of deliveries can be also observed among other suppliers, which might suggest the troubles
with finding raw materials with suitable amount or its palletizing. These are among the most
frequent problems of biomass supply logistics experienced by power plants in Poland.
The problem of quality of biomass supply should also be emphasized as it has direct impact on the
effectiveness of energy generation. Quality requirements concern the form of the biomass delivered
(briquette, pellet), its net calorific value, humidity or ash and sulphur content. They are similar for
biomass of both agricultural origin and the biomass from forestry. These requirements are
individual requirements defined by the analysed enterprise and connected with the equipment for
biomass co-firing installed in their facilities and the demands of environmental protection imposed
by state government regulations.
Table 5 The number of deliveries that have not met individual quality requirements
Calorific Value
Humidity
Ash Content
Sulphur Content
July
3
14
18
2
August
2
13
22
1
September 3
15
38
0
October
3
18
37
1
November 4
32
44
0
December
10
58
72
5
Total
25
150
230
8
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As can be noted, the highest number of non-conforming deliveries is connected with the criterion of
ash content (Table 5). Furthermore, a great number of deliveries do not meet the humidity
requirements. As results from the source documents, the value of this parameter exceeded the upper
limit (12%) in all the non-conforming deliveries. The volume of non-conforming deliveries with
respect to sulphur content was insignificant, which is particularly important due to the
environmental protection requirements the enterprise must meet. Other parameters relate mainly to
the requirements of the enterprise connected with the co-firing equipment installed in the
enterprise's facilities. If these requirements are not met, it might lead to the problems with
electricity generation, but it does not significantly affect the enterprise's environment e.g. the
problems of air pollution with harmful substances.
Analysis of the problem of non-conforming deliveries in individual months reveals that the number
of the deliveries which do not conform to the quality requirements is on the increase. This is likely
to be caused by weather conditions the biomass is obtained, which has considerable impact on
biomass quality. The increasing number of non-consistent deliveries might also result from lower
motivation of suppliers and neglecting the problems of preparation of high-quality biomass.
Undoubtedly, the fact that the enterprise accepts such low-quality deliveries has significant effect
on these practices. Therefore, the enterprise should be more consistent in exacting the quality
requirements for the biomass delivered and, if the installation for biomass firing is capable of being
operated with lower-quality fuels, the enterprise managers should re-consider lowering the
requirements. Constant acceptance of non-consistent deliveries reduces the enterprise's credibility
and encourages suppliers not to respect the requirements.
Analysis of the number of the deliveries that have not met quality requirements should also include
the division into the deliveries of agricultural and forestry biomass. Both types of biomass have
slightly different content, which causes that they might have different quality properties. Share of
non-conforming deliveries with respect to this division is presented in Table 5.
Table 5. Share of non-conforming deliveries with respect to the division into agricultural and
forestry biomass.
Month
Share of non-conforming
July
Agricultural Biomass
68.18
Forestry Biomass
11.69
0.00
August
95.65
September
88.37
3.08
October
November
91.67
95.12
9.80
16.36
December
96.82
25.37
July-December
92.03
12.24
The data presented in the table show that the biomass of agricultural origin is characterized by a
considerable higher coefficient of improper deliveries. This level is lower than 70% in July,
whereas it fluctuates around 90-95% in other months. Only insignificant percentage of deliveries of
agricultural biomass meets the quality requirements imposed by the analysed enterprise. The
deliveries of the biomass of forestry origin meet these requirements to higher extent. Therefore, it
should be reconsidered whether the requirements defined by the enterprise with respect to the
biomass of agricultural origin are not exaggerated and whether they should not be changed
compared to the forestry biomass. It should not be assumed that the non-conformance of
agricultural biomass deliveries was caused exclusively by the supplier's negligence and disrespect
for the requirement. It is more likely that these requirements are maladjusted to the characteristics
of biomass of agricultural origin and only some deliveries are able to meet them.
Choosing the suppliers, their assessment and delivery organization are not the only problems in the
area of supply logistics. Another aspect of supply logistics that might have a direct impact on the
efficiency of electricity production form solid biomass is organization of the process of
warehousing. The process of warehousing directly affects quality properties of biomass, such as
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humidity, ash content and, consequently, net calorific value. As results from comparative analysis
for the quality parameters measured before and after the process of warehousing, this process might
have both positive and negative effect. This concerns the quality parameters of both agricultural
biomass and the biomass of forestry origin. Storage of biomass in suitable conditions might
contribute to the decrease in biomass humidity, and, consequently, to the increase in its calorific
value. However, insufficient conditions might have an opposite effect. Warehousing processes do
not significantly affect ash and sulphur content, but biomass contamination during warehousing
might cause the increase in ash content, which might be higher than the potential benefits of the
reduced humidity. Despite several positive aspects of biomass warehousing, its longer storage
generates the risk of deteriorated quality properties. Therefore, it seems that the satisfactory results
of the effect of biomass warehousing in the present manner do not provide sufficient ground for the
enterprise to increase storage area or elongate the storage time for the biomass used for energy
purposes.
As mentioned above, the enterprise purchases the biomass as a package with the deliveries.
Therefore, there is no need to consider the problems of transport management. The focus should be
on re-considering replacing the road transport used in the enterprise into the theoretically cheaper
rail transport. However, it is essential that both the power plant and the suppliers should have a
siding, which would allow for avoiding the costs of loading and unloading and using road transport
at initial and final sections of the route.
Conclusions
The biomass utilization in power energy plant supply is more and more important in the situation of
sustain development strategy introduction. However is it extremely important to noticed real effects
of the strategy introduction with effects of logistics activities those are not simply positive on the
financial effects of power plant and environment. The power plant location process will not
generally include consideration of biomass sources availability and in effects it brings problems
with rising logistics costs and negative environmental effects. Therefore it is suggested in the power
plant localization process to include scientific methods [3,4, 9, 10] to improve economy, logistics
and environmental efficiency.
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