The results again show a significant influence of the fuel blend and vehicle/fuel per­formance, with net GHG emissions ranging from 0.055 kg CO2 eq./km (E10-1, i. e., ethanol used as E10 based on actual test data) to 0.120 kg CO2 eq./km (E-3, i. e., energy basis), that is., from —77% to —49% with respect to gasoline, respectively. When taking into account actual fuel performance (from vehicle tests), E10 indeed appears to be the most favorable way of using fuel bioethanol as far as GHG emissions are concerned. This means that when considering a given volume of bioethanol to be introduced in a country, region or com­pany, the most significant reduction of GHG emissions will be achieved by using the ethanol as E10. When comparing the net GHG emissions of fuel blends (and not only of the bioethanol component in the fuel blends), E85 leads to the most significant reduction of GHG emissions, before E10 and E5 in this order (in relation to the ethanol content in the fuel blend and the amount of gasoline displaced).

In case of lack of actual vehicle test data, option E-2 (equivalent to fossil reference on a vol­ume basis) is undoubtedly the best choice for lower rates of ethanol incorporation (i. e., E5 to E20), while option E-3 (equivalent to fossil reference on an energy basis) is more appropriate for higher rates of incorporation (i. e., E85 to E100). In both situations however, options E-2 and E-3 lead to an underestimation of bioethanol merit (including the reduction of GHG emissions but also the reduction of nonrenewable energy consumption). In a very large majority of cases, E-3 (i. e., energy basis) is the choice adopted to take into account the utiliza­tion phase in a WtW approach.

When considering E5 (resp. E10) as the fuel blend, the error induced by choosing option 2 instead of option 1 is of the order of 20% (resp. 45%) to the disadvantage of ethanol. When considering E85 as the fuel blend, the error induced by choosing option 3 instead of option 1 is in the order of 3%, still to the disadvantage of ethanol. E-3 also leads to a small error when assessing the GHG balance of biodiesel, regardless of the incorporation rate.