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INTERNATIONAL JOURNAL OF ENERGY RESEARCH Int. J. Energy Res. 2006; 30:763–775 Published online 23 January 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/er.1182

An economic and environmental assessment of biomass utilization in lignite-fired power plants of Greece P. Grammelis1,2,n,y, G. Skodras1,3,4 and E. Kakaras1,2 1

Institute for Solid Fuels Technology and Applications/Centre for Research and Technology, Hellas, Ptolemais, Greece 2 Laboratory of Steam Boilers and Thermal Plants, School of Mechanical Engineering, National Technical University of Athens, Athens, Greece 3 Laboratory of Solid Fuels and Environment, Chemical Process Engineering Research Institute, Thessaloniki, Greece 4 Chemical Process Engineering Lab, Aristotle University of Thessaloniki, Thessaloniki, Greece

SUMMARY The environmental and socio-economic impacts of biomass utilization by co-firing with brown coal in an existing thermoelectric unit in Greece or through its pure combustion in a new plant were studied and evaluated in this work. The 125 MWe lignite-fired power plant in Ptolemais Power Station (Western Macedonia) was used as reference system. The environmental benefits of the alternative biomass exploitation options were quantified based on the life cycle assessment methodology, as established by SETAC, while the BIOSEM technique was used to carry out socio-economic calculations. The obtained results showed clear environmental benefits of both biomass utilization alternatives in comparison with the reference system. In addition, co-firing biomass with lignite in an existing unit outperforms the combustion of biomass exclusively in a new plant, since it exhibits a better environmental performance and it is a low risk investment with immediate benefits. A biomass combustion unit requires a considerably higher capital investment and its benefits are more evident in the long run. Copyright # 2005 John Wiley & Sons, Ltd. KEY WORDS:

life cycle assessment; energy; biomass; power plant

1. INTRODUCTION Renewables in Greece account for about 5% of total primary energy supply (1.36 Mtoe), or 2.8% excluding large hydro. According to the Kyoto protocol, the share of renewables in the energy sector of Greece is expected to increase up to 20%, by 2010. The distribution of the Greek units in relation to the biomass species used for the production of thermal energy is shown in Table I (Alexopoulos et al., 1999; NTUA-LSB, 2002). Although the participation of biomass in the Greek energy market is still very low, i.e. about 25 MWel, the construction of new biomass power stations is anticipated, rising the total installed capacity up to 500 MWel till 2010. The potential of biomass in the entire country is up to 9 278 000 dry tons, out of which n

Correspondence to: P. Grammelis, Laboratory of Steam Boilers and Thermal Plants, School of Mechanical Engineering, National Technical University of Athens, Heroon Polytechniou St. 9, 15780 Athens, Greece. y E-mail: [email protected]

Copyright # 2005 John Wiley & Sons, Ltd.

Received 11 March 2005 Revised 21 September 2005 Accepted 7 October 2005

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Table I. Thermal units using biomass in Greece. Type

Number of units

Consumption (tons)

Thermal energy (MW h y1)

Biogas combustion Food industry residues Sewage treatment plants

6 3 3

} } }

21 495 8667 12 828

Residue combustion Wood residues Cotton ginning residues Dry olive kernels Husks/kernels Rice residues Straw

2720 58 18 2633 3 7 1

632 274 99 138 28 138 500 000 612 4330 56

2 811 500 380 278 83 889 2 325 556 3194 18 333 250

5.5 million dry tons are herbaceous crop residues, 3.1 million dry tons are ligneous crops, 0.4 million dry tons are olive husks and 0.13 million dry tons of cotton ginning residues. Most important crops in the regions around the lignite-fired power plants are durum wheat, soft wheat, barley and olive trees. About 191 thousand tons of dry biomass that account for 3.25 T Jth (or 77.7 Mtoe) are available for energy production in the Ptolemais-Kozani area of Western Macedonia in Greece, where six brown coal power stations of 4.4 GWe are located. The substitution of lignite in existing power plants or the combustion of biomass in new thermal plants are considered as the most promising and low risk ways for the energy exploitation of biomass (Hartman and Kaltschmitt, 1999; Krotscheck et al., 2000; Rafaschieri et al., 1999). In this paper, both biomass co-combustion in an existing power plant and in a new biomass-fuelled unit were analysed and compared regarding social, economical and environmental impacts. A lignite fired unit of 125 MWe existing in Ptolemais power station (total installed capacity 620 MWe) was used as a reference system. The BIOmass Socio-Economic Multiplier (BIOSEM) technique was applied for the economic and socio-economic calculations, while the environmental impact was evaluated through a life cycle analysis (LCA). Advantages and disadvantages of each test case were summarized and the benefits were quantified in order to assess the most efficient method, as concerns the biomass utilization for power production. The investigated scenarios are the following: (i) Construction modifications in one operating lignite-fired thermoelectric unit, which will be converted to a co-firing unit using blends of lignite and biomass in the proportion of energy contribution 90–10%, respectively. (ii) Construction of a new biomass combustion plant of the same nominal capacity that will come from biomass introduction in the co-firing plant.

2. METHODOLOGY 2.1. Goal and scope definition and description of scenarios The scope of the present study is to assess the differences in economics and environmental impact on the Ptolemais region, when introducing biomass as fuel for electricity generation. Copyright # 2005 John Wiley & Sons, Ltd.

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Two alternatives for biomass utilization are examined, which are depicted in the following test cases: (a) Reference system: existing lignite-fired power plant in the Ptolemais Power Station, of maximum power output of 125 MWe, availability 8000 h per year and nominal load of 100 MWe. (b) Construction and operation of a new plant for electricity generation in the area of the Ptolemais Power Station, of maximum power output of 12.5 MWe, availability 8000 h per year and nominal load of 10 MWe, which will operate only on biomass from agricultural residues. Obviously, the new plant will be operating in parallel to the existing lignite-fired one, resulting in total maximum power output of 137.5 MWe. (c) Modifications of the reference plant in order to burn blends of lignite and agricultural residues in the proportion of 90/10 (% thermal input). 2.2. Financial analysis BIOSEM is a technique that quantifies the social and economic impact on the region from the operation of a power plant in the area, using exclusively biomass (ETSU, 1998). Collecting relatively recent information on the economic state of the region is the most difficult task and often requires the use of data covering a wider geographical region, since the situation of the specific area of immediate interest is rarely well known. Among the three available versions, the BIV8-PER, which is suitable for wood and agricultural residues, was used in this study. Cash flow analysis and investment techniques are used to determine the profitability of both fuel production and utilization activities. In the agricultural sector, full displacement effects are calculated for the displaced activity and any downstream processing activity. On the contrary, displacement effects are not calculated in the energy sector as the effects of individual bio-energy projects are assumed to be small compared to the overall size of the energy sector. More details about BIOSEM are given in ETSU (1998). 2.3. Life cycle analysis (LCA) LCA given by SETAC (Society for Environmental Toxicology and Chemistry) was applied towards the environmental impact assessment of the biomass utilization systems (Fava, 1991; Meier, 1997; Vigon, 1993). Based on its definition, LCA is a continuous process of environmental impact evaluation that could be implemented not only at the sum of corporation activities, but also at a single activity or the production chain of only one product, and aims at reducing the environmental impact caused. Normally, LCA consists of four stages (Fava, 1991; Kaltschmitt et al., 2000): (1) (2) (3) (4)

Goal and scope definition, as already described above. Inventory analysis. Impact assessment. Improvement analysis.

The four LCA stages are interrelated and, thus, there is the eligibility to return to previous stages of the process during the analysis and make improvements on the system, modify the initial assumptions or examine whether additional changes are needed. 2.3.1. Inventory analysis. More detailed data records of the examined system are compiled in this stage. An overall depiction of the system is presented in Figure 1. Copyright # 2005 John Wiley & Sons, Ltd.

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Input

System Boundaries

Output Energy

Collection of Raw Materials

Energy

Production of Materials

Emissions

Materials Use, Re-use, Maintenance

Products

Wastes treatment

Figure 1. Model system in LCA.

System Boundaries Emissions

Electricity Diesel

Production and Collection of Fuels

Emissions

Emissions

Biomass Lignite

Biomass

Transportation of Fuels

Electricity

Diesel

Combustion at the Plant

Electricity

Lignite

Electricity

Figure 2. Representation of the system model used in LCA.

Each system is divided into three subsystems to further simplify the analysis (Hartmann and Kaltschmitt, 1999; Gemtos, 1999). These three subsystems are: (1) Production and collection of fuels. (2) Transportation to the plant. (3) Combustion of the fuels at the plant. Figure 2 offers a general and simplified representation of the overall system and its subsystems. It also gives an overview of system boundaries as well as the different input and output flows. The two examined systems are compared with the reference system in order to extract qualitative and quantitative conclusions. All calculated results and especially emissions are reduced to a common reference, i.e. 1 MW h of electrical power. Moreover, the plant construction and demolition stages are not taken into account since their impact on the system could be considered negligible without significant alterations on the final Copyright # 2005 John Wiley & Sons, Ltd.

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results. The pre-existing processes that are not altered by the plant construction, as well as those being common to all systems are not considered within the LCA. As a result the examined systems are simplified, since the goal of LCA is not to conduct an isolated analysis of environmental impact, but to allow the comparison among the systems examined and the reference system. The individual consumption required for the system operation is provided by the electrical power produced in the plant and consequently, the power delivered to the grid and the system efficiency are reduced. Finally, the ‘neutral’ behaviour of biomass as to CO2 emissions and the greenhouse effect should be emphasized. The fuels that were used during this analysis are: Lignite: is extracted from the mines in Ptolemais region and its net heating value is 6000 kJ kg1. It is burnt in the steam boilers of the lignite-fired and the co-firing plants. Biomass: comes from agricultural activity residues in the Ptolemais region and its net heating value is 15 000 kJ kg1. It is the fuel of the steam boilers in the biomass-fired and the co-firing plants. Diesel: is used to fuel the trucks carrying biomass, the tankers supplying the mine with diesel and the machinery used for lignite mining. 2.3.2. Impact assessment. The third stage of LCA comprises the environmental impact assessment and the consequences on the inhabitants’ health safety of the system, based on the data already collected in the two previous stages. Impact assessment within LCA is made up of four stages according to the SETAC methodology: (1) (2) (3) (4)

Classification. Characterization. Normalization. Assessment.

The categories within the impact assessment are the following: (1) Global warming potential (GWP): It expresses the impact caused by the system operation on the greenhouse effect and the weighted amount of greenhouse gases is stated in kg CO2-equivalents (Kaltschmitt et al., 2000). (2) Acidification potential (AP): It expresses the environmental impact caused by acid gas emissions in the atmosphere. Namely, the pollutants taken into account are SO2, NOx, NH3, HCl and HF and their weighted sum is stated in kg SO2-equivalents (Kaltschmitt et al., 2000). (3) Eutrophication potential (EP): It refers to water enrichment with nutrients, mainly with nitrogen and phosphor, causing faster growth to high-class flora and consequent disorder, and degrading water. It is measured in kg N-equivalents. (4) Photochemical ozone creation potential (POCP): It expresses the system impact on the photochemical creation of ozone due to gas emissions and is measured in kg C2H4equivalents. (5) Human toxicity in the air compartment (HTA): In general, the toxicity potential is determined as the product of the emitted substance’s quantity and the latter’s equivalency factor for exposure through air, soil and water. The potential is expressed in (m3) of air, soil or water and corresponds to the volume of the compartment (air, soil or water) into Copyright # 2005 John Wiley & Sons, Ltd.

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which the emission should be diluted for its concentration to be so low that no toxicological effects could be expressed from the emission. Consequently, HTA refers to toxic substances deposition in the air and is measured in m3 of air. (6) Human toxicity in the water compartment (HTW): It refers to toxic substances deposition in the water and is measured in m3 of water. (7) Human toxicity in the soil compartment (HTS): It refers to toxic substances deposition in the soil and is measured in m3 of soil. The last stage of impact assessment includes the attempt to evaluate the gravity of the effects of system operation. Three indicators are calculated for each of the examined systems, which provide an overview of fuel utilization both in the power production plant and the whole system. These are the following: (1) Total system efficiency: Total system efficiency is the ratio of the power produced by the system to the energy consumed. It also considers all the fuels used in the system as follows: Ztotal ¼

Ea Ec El þ Eb þ Ed

ð1Þ

(2) Life cycle efficiency: The energy equilibrium in the system to the energy consumed is defined through life cycle efficiency. Since the energy contained in the fuel is greater than the electric power produced, the energy equilibrium for the system and subsequently the specific indicator is always negative. However, fuels not directly used for power production, such as diesel, are not taken into account, i.e.: ZLifeCycle ¼

Ea Ec El Eb El þ Eb

ð2Þ

(3) Net energy ratio: Since biomass constitutes a renewable energy resource, as opposed to lignite and diesel, this indicator expresses the energy produced to the energy contained in non-renewable fuels, i.e.: NER ¼

Ea El þ Ed

ð3Þ

3. RESULTS AND DISCUSSION 3.1. Financial analysis Several interesting conclusions are drawn when comparing the two alternative scenarios. The initial investment to modify the lignite-fired plant is appreciably lower}as low as about 10%}than that required for building a brand new biomass plant. The investment cost can be further increased if the enhanced requirements for storage facilities and the land required to build the new plant are to be considered. According to the BIOSEM forecast, the biomass combustion plant yields profits reaching 11.7 million h in the first 20 years of operation. Following the profitability rate, the profit of the project is expected to exceed 20 million h by the end of the plant technical lifetime, estimated at 30–35 years. On the contrary, the co-firing plant will ‘squeeze’ the corporation profits from the specific plant for the next 10 years, i.e. by the Copyright # 2005 John Wiley & Sons, Ltd.

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end of the technical life time of the lignite-fired plant. Extending the plant technical life span by 10–15 years will bring about an additional profit of 4.5–7 million h: The willingness of the rural population to help in the collection of the required biomass quantities towards the smooth operation of the power plants is another crucial factor for both scenarios. Several projects have nearly failed due to the refusal of the local population to assist or by their attempt to overprice biomass (EC-DGXVII, 2000; Forsberg, 2000; Jenkins and Sumner, 1986). As a result, the new biomass combustion plant appears to be a precarious investment, since any shortcoming in biomass collection will result in faulty operation. On the other hand, it is possible to substitute biomass with lignite at the co-firing plant and, thus, sustaining smooth operation. Government support is essential to the successful completion of both projects in combination with subsidies and tax exemptions to motivate the rural population and secure their support. The economic benefits for the inhabitants of the region and mainly the rural population are significant in both scenarios and especially when the construction of a new plant is considered. The latter arises from the demand of 10 000 tons of biomass on annual basis and the jobs offered to the inhabitants from the construction of a new plant. The social impact of the implementation of the two scenarios is also noteworthy. The operation of the new plant will bring about 200 new jobs that will be allocated mostly by inhabitants of the Ptolemais area. If the lignite-fired power plant is modified to co-fire, the new jobs offered will be significantly fewer and estimated around 80. However, the jobs in the existing plant will be secured for another 10–15 years and in this way both scenarios will have similar effects for the region in the long run. It can be concluded that the modification of an already existing lignite-fired plant to make use of lignite blends with agricultural residues involves less investment risk and constitutes a safer alternative for the plant owner. On the other hand, the construction of a new biomass combustion plant appears to have more financial advantages both to the corporation and the inhabitants of the region. Moreover, both scenarios will have similar effects on the employment rate in the area in the long run. Obviously the biomass combustion plant has more long-term advantages as opposed to the co-firing plant, which appears to have significant short-term benefits. 3.2. Environmental impact assessment The final results of LCA are presented in Table II. Figures 3–6 comprise a qualitative and quantitative comparison of the co-firing system and the mono-combustion (biomass- and lignite-fired) systems so as to quantify the environmental impact of producing 1 MW hel for each system and assess the total impact of both systems on the region. The results for the energy indicators of each system are presented in Table III. The most significant conclusions to be drawn based on the energy indicators for the three systems examined are as follows: (1) The co-firing system has higher total efficiency ratio as compared to both the reference system and the biomass-fired system, indicating that the energy input is more efficiently used in this case. (2) The estimated life cycle efficiency of the co-firing system is much higher. The energy loss is lower compared to the other two systems and the energy input for power production is more efficiently used. Copyright # 2005 John Wiley & Sons, Ltd.

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Table II. Assessment results. Reference system

Biomass-fired and lignite-fired systems

Co-firing system

0.177 0.0559 0.0137 0.662 83.9 8.73 9.34 1004

0.161 0.0536 0.0144 0.602 80.1 8.33 8.86 1004

0.160 0.0530 0.0142 0.596 79.1 8.24 8.75 1004

Impact category GWP (kg CO2-equivalents MW h1 el ) AP (kg SO2-equivalents MW h1 el ) EP (kg N-equivalents MW h1 el ) POCP (kg C2H4-equivalents MW h1 el ) HTW (m3 of water MW h1 el ) HTS (m3 of soil MW h1 el ) HTA (m3 of air MW h1 el )

Combustion

Transport

Production

GWP [kgCO2 -equiv/MWhel]

1200 1000 800 600 400 200 0 Reference System

Mono-combustion Mixed Combustion Systems System

Figure 3. Schematic representation of each subsystem contribution to GWP at the characterization stage.

AP [kgSO2- equiv/MWhel]

Combustion

Transport

Production

4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Reference System

Mono-combustion Systems

Mixed Combustion System

Figure 4. Schematic representation of each subsystem contribution to AP at the characterization stage.

(3) The higher net energy ratio of the co-firing system corresponds to reduced input by nonrenewable energy resources for power production. Moreover, it is proved that this system contributes less than the other two systems to the depletion of natural resources such as lignite. Copyright # 2005 John Wiley & Sons, Ltd.

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Combustion

Transport

771

Production

EP [kgN-equiv/MWhel

3.5 3 2.5 2 1.5 1 0.5 0 Reference System



Figure 5. Schematic representation of each subsystem contribution to EP at the characterization stage.

POCP [kgC2 H4 - equiv/MWhel]

Combustion

Transport

Production

12 10 8 6 4 2 0 Reference System



Figure 6. Schematic representation of each subsystem contribution to POCP at the characterization stage. Table III. Energy indicators for all systems. Indicator Total system efficiency Life cycle efficiency Net energy ratio

Reference system

Biomass-fired and lignite-fired systems

Co-firing system

0.1947 0.7475 0.2913

0.2420 0.7516 0.2912

0.2467 0.7466 0.3236

3.3. Improvement analysis The modification of the lignite-fired plant to a co-firing unit brings about a 10% substitution of lignite from biomass. The environmental impact on the region coming from the plant operation is the sum total of the impact caused from biomass use, which is positive, and the gain due to the reduced amount of lignite used for the 10 MWe production (Hartmann and Kaltschmitt, 1999; Maurice et al., 2000), i.e.: S ðimpactÞ ¼ ðimpact of Biomass UseÞ þ ðimpact of Lignite SubstitutionÞ Copyright # 2005 John Wiley & Sons, Ltd.

ð4Þ

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GWP [kgCO2-equiv./MWhel]

-0.16 -0.14 -0.12 -0.10 -0.08 -0.06 -0.04 -0.02 0.00

Biomass combustion plant

Mixed combustion plant

0.02

Biomass combustion plant (heavy oil substitution)

Figure 7. Total impact on GWP for the examined systems.

AP [kgSO2 - equiv. / MWhel] -0.03 -0.02 -0.01 Biomass combustion plant 0.00

Mixed combustion plant Biomass combustion plant (heavy oil substitution)

0.01 0.02 0.03

Figure 8. Total impact of AP for the examined systems.

When a new biomass combustion plant is constructed, the additional impact on regional basis is calculated based on the biomass use: S ðimpactÞ ¼ ðimpact of Biomass UseÞ

ð5Þ

In order to keep the Greek energy matrix constant, the contribution of the various fuel sources for power production will change. Namely, the operation of the new biomass combustion plant will lead to the reduction of the power production by another plant on national level. Taking into account the high cost of power production from heavy oil, it is assumed that the 10 MWel Copyright # 2005 John Wiley & Sons, Ltd.

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x 10-3 20

773

EP [kgN - equiv. /MWhel]

18 16 14 12 10 8 6 4 2 0 Biomass combustion plant



Figure 9. Total impact on EP for the examined systems.

POCP [kgC2H4 -equiv./MWhel] -0.60 -0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10

Biomass combustion plant



Figure 10. Total impact on POCP for the examined systems.

resulting from biomass combustion will substitute the load from a heavy oil power plant. As a consequence, the environmental impact from the operation of the new biomass combustion plant on national level arises not only from biomass use, but also from the non-use of heavy oil and is expressed as follows: S ðimpactÞ ¼ ðimpact of BiomassUseÞ þ ðimpact of Heavy Oil SubstitutionÞ

ð6Þ

The final results are presented in Figures 7–10. Copyright # 2005 John Wiley & Sons, Ltd.

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4. CONCLUSIONS Co-firing of biomass and lignite for electricity generation were compared in terms of economics and environmental impact. Within this analysis, there is comparative assessment of the advantages and disadvantages of each case and quantification of benefits, aiming to assess which method is more efficient as to biomass utilization for power production. In order to achieve a more realistic approach, the study was conducted for the region of Ptolemais, Greece, where the Ptolemais Power Plant with total installed capacity of 620 MWe is situated. From an economical point of view, co-firing biomass in a lignite-fired power plant is an investment of low risk, as it requires a small capital, offering at the same time immediate benefits to the company and the inhabitants of the region. A significant capital investment is needed for the construction of a new biomass combustion plant, which constitutes an important business venture. Nevertheless, considerable financial benefits can be accrued for the corporation and the inhabitants in the long run. The social impact is estimated to be similar in both scenarios of biomass exploitation. The operation of the new plant will create increased number of new jobs for the local residents. The modification of the lignite-fired plant will bring about fewer jobs but will secure the existing jobs for another 10–15 years, due to the extension of the plant technical lifetime. As far as the environmental impact is concerned, the co-firing plant outperforms the biomass combustion plant. The comparison between the two options proves that the co-firing plant offers cleaner electrical power with lower pollutant emissions. On a power production basis, the co-firing plant appears to be more beneficiary. Special reference should also be made to the conservation of natural resources achieved with the reduction of the lignite consumed. As a result, the co-firing plant enables more efficient use of biomass as fuel for power production compared to the biomass combustion system. Although, there are slight differentiations in the examined systems in terms of the socio-economic impact, the environmental impact induced is the decisive factor in favour of the co-firing plant. These findings are valid for all lignite fired power plants of Northern Greece. However, co-firing nowadays is not practised extensively in the specific geographical area and the wider Mediterranean region, as biomass combustion is preferred instead. Furthermore, technical and non-technical barriers and legislative restrictions may limit the applicability of this technology. Technical barriers to co-firing projects based on coal and biomass/wastes derived fuels primarily arise from the individual fuel characteristics and quantities, the combustion technology and anticipated operating conditions. Non technical barriers include financial, fuel supply and regulatory}environmental issues. Apart from technical and non-technical barriers, existing legislation is also considered. Directive 2001/77/EC includes in its scope the production of electricity from biomass, being defined as the biodegradable fraction of products, wastes and residues from agriculture, forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste. The use of dangerous and non-dangerous residues is regulated by EU legislation (Directives 94/67/EC, 89/369/EEC and 9/429/EEC), but requires specifications for commercial and regulatory purposes. In addition to the above, the necessity to collect good quality information on the existing biomass installations and its potential in Greece is imperative. Also there is a strong prerequisite for the development of fuel supply networks and the classification and standardization of biomass/waste derived fuels produced in the country. The trading of CO2 certificates will enhance the utilization of such fuels in efficient coal fired power plants. Depending on the origin of the input materials, the electricity costs by Copyright # 2005 John Wiley & Sons, Ltd.

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utilizing biomass/waste derived fuels can be significantly below the EU target of 0:05 h kW h1 at a competitive level. NOMENCLATURE AP Ea Ec El Eb Ed EP GWP HTA HTS HTW NER POCP Zi

=acidification potential (kg SO2-equivalents MW h1 el ) =energy produced by the power plant =energy consumed within the system of power production =energy contained in lignite and exploited for power production =energy contained in biomass and exploited for power production =energy contained in diesel and exploited for power production =eutrophication potential (kg N-equivalents MW h1 el ) =global warming potential (kg CO2-equivalents MW h1 el ) =human toxicity in the air compartment (m3 of air MW h1 el ) =human toxicity in the soil compartment (m3 of soil MW h1 el ) =human toxicity in the water compartment (m3 of water MW h1 el ) =net energy ratio =photochemical ozone creation potential (kg C2H4-equivalents MW h1 el ) =efficiency, where i ¼ total system, life cycle

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