BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

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30 3 Life cycle assessment of biofuels: methods and tools tural reference system is considered as associate reference system (see also the representations of life cycle comparisons in Chapter 2). As already discussed in Gaillard (1996) or Biewenga and van der Bijl (1996) and practised in several studies on biofuels, this way is equivalent to a procedure of avoiding allocation with help of a system expansion (see Chapter 3.2.4), where what it is called here a secondary function would be in reality a co-product. There is no objective reason to theoretically prefer one or the other way of presentation – also because the exact nature of the biofuel under investigation plays a role – and that the end result is the same for the two theoretical options. The economic aspects of the secondary functions are not considered within this part of the discussion. They are dealt with in Chapter 5.2. The detailed list of the functions considered for each investigated biofuel chain and the corresponding reference systems used for the comparisons are given in the Chapters 2.3 to 2.6. 3.2.2 Functional and reference units The functional unit expresses the performance of a system and serves as a reference unit for environmental impacts. The chosen functional unit of 1 MJ useful energy is based on the main function “provision of useful energy”. Since however the various biofuels fulfil different specific purposes – such as heat production, electricity production or transportation – the results can also be expressed in terms of units that express such functions. Table 3-1 below lists such reference units as they are used for the European results and a number of individual countries within this project. For further explanations of these units see also Chapter 3.4.4. Table 3-1 Functional units for each biofuel chain under concern Biofuel Functional unit Triticale for co-firing for electricity 1 kWh electricity Willow for district heating 1 MJ heat Miscanthus for district heating 1 MJ heat RME for transportation 1 km distance driven SME for transportation 1 km distance driven ETBE for transportation 1 km distance driven Traditional firewood for residential heating 1 MJ heat Wheat straw for district heating 1 MJ heat Biogas from swine excrements 1 MJ useful energy (heat and electricity)* Hemp gasification for electricity 1 kWh electricity *during biogas combustion in a CHP (combined heat and power) plant, electricity is produced alongside with heat. In this study the total energy production has been balanced. For the comparison of different biofuels among each other, two further reference units were used, namely “ha of land” for the comparison with regard to efficiency of land utilisation and “MJ of energy saved” with regard to the saving of energy resources respectively (see Chapter 4.2). Units of the secondary functions “treatment of agricultural and forestry residues” and “preservation of land under agricultural practice for social and food security reasons” are kg respectively ha. For the inventory analysis, when collecting, validating and presenting the data for the unit processes dealing with biomass production, the unit ha is much more practical than the functional unit MJ. The energy yield of the investigated biofuel chain is used in order to convert the results into the chosen functional unit. 3.2.3 System boundaries and unit processes For the determination of the system boundaries a standard procedure was defined and applied to all investigated chains (biofuel production systems as well as reference systems used for the comparison) regarding the initial definition and inclusion of the unit processes, the standardisation of the input processes and the level of detail.
3.2 Scope definition of the investigated biofuels 31 Fundamentally, all processes of the life cycle of the investigated products (biofuel and fossil fuel) are involved in the scope of the study. The following exceptions were made: • Human labour • Inputs whose mass is negligibly low compared to the total input mass, provided that they have no well-known environmental impact (for example pesticides were always analysed). In short, the boundaries of the product system contain all unit processes needed for the provision of useful energy in form of biofuel or fossil fuel, including waste management. These unit processes are analysed in detail in accordance with the ISO Norm 14041. In this way, a chain contains various unit processes whose quantification is specific for each country. Standardised process units for all countries and product systems under study were considered for items which are not specific to the biofuel chains (for example provision of energy, provision of raw materials, production of inputs and transport to the product system). Construction of machinery and other infrastructure directly used for the product systems are included in the corresponding unit processes. A list of relevant resources and emissions was drawn up (see Tables 3-2 and 3-3 in Chapter 3.4.3) depending on the environmental relevance, the presence of corresponding impact assessment coefficients and the data availability. Background depositions of heavy metals and nitrogen on agricultural fields are included to calculate the corresponding field emissions. Concerning global warming, CO2 from the atmosphere and the CO2 storage effect are not taken into account. Regarding the non-inclusion of certain impact assessment categories, see Chapter 3.4.1. Figure 3-2 shows the level of differentiation at which the various elements of the systems were considered. Infrastructure and maintenance Buildings barns, sheds Machines tractors Fuel for tractors Agricultural reference system Field preparation Sowing Cutting Organic and chemical inputs Seeds Fossil fuel production system Infrastructure and maintenance Buildings Machines for extraction and mining Fuel for transport Crude oil extraction Transport Storage Processing Combustion Comparison Infrastructure and maintenance Buildings barns, sheds Machines tractors, combines, processing plants Fuel for tractors Biofuel production system Field preparation Sowing / planting Fertilising Crop protection Harvesting Baling / chipping Transport Storage Processing Combustion Organic and chemical inputs Seeds or Cuttings Mineral fertiliser N, P2O5, K2O, lime Biocides Pesticides, Herbicides Fungicides Figure 3-2 Schematic representation of a life cycle comparison showing the level of detail considered. The example chosen here is that of oil from fossil resources and a cultivated biofuel.
Page 1 and 2: BIOENERGY FOR EUROPE: WHICH ONES FI
Page 3 and 4: Contents Executive summary.........
Page 5: Contents III 5.3.2 Variation in col
Page 8 and 9: 2 Executive summary Table 1 Investi
Page 10 and 11: 4 Executive summary Result of the c
Page 12 and 13: 6 Executive summary Economic aspect
Page 15 and 16: 1 Goals, target groups and general
Page 17: 1 Goals, target groups and general
Page 20 and 21: 14 2 Biofuels under study The resul
Page 22 and 23: 16 2 Biofuels under study 2.3 Life
Page 24 and 25: 18 2 Biofuels under study 2.3.3 Mis
Page 26 and 27: 20 2 Biofuels under study 2.4.2 Sun
Page 28 and 29: 22 2 Biofuels under study 2.5 Life
Page 30 and 31: 24 2 Biofuels under study 2.5.3 Bio
Page 33 and 34: 3 Life cycle assessment of biofuels
Page 35: 3.2 Scope definition of the investi
Page 39 and 40: 3.2 Scope definition of the investi
Page 41 and 42: 3.3 Inventory analysis 35 then. Eve
Page 43 and 44: 3.3 Inventory analysis 37 using the
Page 45 and 46: 3.4 Impact assessment 39 energy cro
Page 47 and 48: 3.4 Impact assessment 41 The IPCC p
Page 49 and 50: 3.5 Interpretation 43 of the indivi
Page 51 and 52: 3.5 Interpretation 45 Fossil fuel p
Page 53 and 54: 4 Environmental results: presentati
Page 55 and 56: 4.1 Introduction 49 case excluding
Page 57 and 58: 4.2 European results: biofuels comp
Page 69 and 70: 4.3 European results: biofuels for
Page 75 and 76: 4.4 Summary of country specific res
Page 83: 4.5 Summary of comparisons between
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80 5 Socio-economic and political a
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90 6 Conclusions and recommendation
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7 Annex 7.1 Country specific life c
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7.1 Country specific life cycle com
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7.2 Comparisons between the countri
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7.4 List of authors and addresses 1
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7.5 Data availability 175 7.5 Data
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7.6 Literature 177 Hauschild and We
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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

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