The production of bioethanol from wheat grains gives rise to coproducts both at the agri­cultural stage (i. e., wheat straw) and at the industrial stage (i. e., wheat DDGS). Both coproducts may be used as animal feed or as fuel (Kaparaju et al., 2009). According to the most common practice in the European context, the reference use of the coproducts is consid­ered to be animal feed. It is here considered that the land where the animal feed (baseline) was initially produced (now displaced by straw and DDGS) is turned into set-aside land. Simi­larly, it is considered in this reference framework that wheat is grown on land that was initially set aside (incl. green cover with no farming inputs). The corresponding systems are shown in Figure 1. When allocation is applied, the "from" (reference) and "to" (studied) systems are illustrated as in Figure 2 (showing the effect of allocation). When substitution is applied, the "from" and "to" systems are illustrated as in Figure 3, where the substituted products and the associated land use are included in the system studied with a negative impact in order to keep the reference system identical in all cases (i. e., limited to the produc­tion and use of gasoline). The effect of different allocation/substitution choices is investigated in the case study section.

The WtT GHG net GHG emissions of unleaded gasoline in the Swiss context are taken from ecoinvent and are equal to 0.018 kg CO2 eq,/MJth (i. e., 0.782 kg CO2 eq./kg or 0.586 kg CO2 eq./l) at the service station.