5 years ago



30 3 Life cycle

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.

Bioenergy Update 10-02 - General*Bioenergy
Maximising the environmental benefits of Europe's bioenergy potential
Bioenergy Value Chain Research And Development Stakes ... - FARA
LCA of a biorefinery concept producing bioethanol, bioenergy - avniR
Desktop Management Tools — Which One Is the Best?
Choose The One That Best Fits Your Lifestyle! - Java Fundraiser
One Size Fits One: Best Practices for Building - Right Management
Hot vs. Cold Ionization Gauges: Which One is Best for Me?