The effect of various methodological choices on the GHG and energy balance of bioethanol is evaluated, with an emphasis on allocation methods, land-use change, fuel blends, and vehicle/fuel performance. Each of these aspects is now explained in more detail.

1.2.1 Allocation Methods

Various allocation methods were investigated, including allocation by energy content, eco­nomic value, carbon content, dry mass, and substitution. The properties and prices of the coproducts are given in Table 4. Four various substitution scenarios are considered, namely: S-1) both straw and DDGS as animal feed, S-2) straw as animal feed and DDGS as fuel, S-3) straw as fuel and DDGS as animal feed, and S-4) both straw and DDGS as fuel. Each of these scenarios gives rise to a specific system definition (incl. the reference system). The "from" (reference) and "to" (studied) systems in the case of allocation (regardless of the method) and substitution (S-1) are illustrated in Figures 2 and 3, respectively.