The results indicate a strong influence of the choice of allocation method, with net GHG emissions ranging from -0.016 kg CO2 eq./km (S-4, i. e., substitution with both straw and DDGS as fuel) to 0.151 kg CO2 eq./km (S-1, i. e., substitution with both straw and DDGS as animal feed), that is, from -107% to -36% with respect to gasoline, respectively. In all cases, however, the net GHG emissions of bioethanol are lower than those of gasoline (0.237 kg CO2 eq./km), with a percentage reduction of 36% in the "worst" case. The negative value in S-4 is explained by the fact that both the straw and the DDGS are replacing fossil energy agents for combined heat and power (CHP) applications. The electricity mix considered is that of Switzerland as reported in ecoinvent, while fuels for heat applications include 53% fuel oil and 47% natural gas (corresponding to the fuel mix in Switzerland). In S-1 and S-3 (i. e., substitution with straw as fuel and DDGS as animal feed), however, DDGS replace soybean meal (imported from Brazil and the US in equal shares, with a ratio of 0.82 kg of soybean meal per kg of DDGS based on dry weight protein content), where soybean oil is considered to be used as a feedstock for biodiesel production and to replace diesel fuel (substitution is applied over the global system). The con­sequence of using DDGS as animal feed in place of soybean meal is therefore unfavorable, showing on the net GHG emissions of bioethanol in S-1 and S-3.

As far as allocation methods are concerned, A-1 (energy), A-3 (carbon) and A-4 (dry mass) produce similar results, with net GHG emissions a lot more favorable than A-2 (economy). This is explained by the fact that wheat grains, straw, and DDGS have similar LHV and car­bon contents. In this particular case of wheat to ethanol, the net GHG emissions in A-2 are not particularly sensitive to ethanol and grain prices. Increasing both prices by 50% results in an increase of the net GHG emissions by only 3% (allocation to grains with respect to straw and ethanol with respect to DDGS being already close to 100%).