The definition of the term ‘allocation’ and the allocation methods used in LCA are given in the Appendix. The allocation issue arises in systems where biofuels are co-produced with other outputs, such as electricity and/or heat so that the impacts have to be allocated between the co-products in an appropriate way. As shown in Table 3.2, most international approaches favour either allocation based on energy

3.4 GHG savings for bioethanol from different feedstocks and country of origin (DfT, 2009; Edwards et al., 2008; Fehrenbach et al., 2007).

content (net calorific value) or system expansion. In the latter, the system is credited for producing the additional output. However, the methodological difficulty is in identifying the ‘correct’ way to credit the system. For example, if the electricity is co-produced with the biofuel in an EU country, the question is what electricity mix should be used to credit the system: best available technology, the average national or EU energy mix? The choice of the allocation method and the ‘credit’ are of the utmost importance as often very different results are obtained using different approaches. In any case, this should be examined as part of the sensitivity analysis (see the Appendix and the textbox).

The EU RED (EC, 2009) favours allocation based on the energy content of biofuels, although other allocation procedures, such as system expansion or

Rapeseed Sunflower Soya Palm oil Waste

Biodiesel feedstock

3.5 GHG savings for biodiesel from different feedstock and country of origin (DfT, 2007; Edwards et al., 2008; Fehrenbach et al., 2007). For legend, see 3.4.

economic value might be more appropriate in particular cases. For example, energy allocation cannot be applied in systems where biofuel co-products do not have an energy value but have an economic value, e. g. ash and fertilisers. In these cases, allocation based on the economic value may be more appropriate. However, this produces volatile results in line with economic values of commodities and should be used only where other allocation methods cannot be applied (ISO, 2006b).

An example of how to allocate environmental impacts using two different bases — mass and energy — can be found in the textbox on pages 46-47.