The methodology and results of three relevant and extensive studies of the global warming potential of various biomass-based fuels are discussed and plotted together, along with the conventional fossil fuels (both gasoline and diesel). These “well-to-tank” GHG emission assessments are based on the assumption of unchanged land use. In this respect, relatively good homogeneity of results is observed for the plant-based ethanols. Global warming potential of biomass-based esters is subject to more contrasted estimations, due to many possible assumptions regarding the substituted products, including fossil transport fuels, as well as animal feed and electricity. On the tank-to-wheel side, CO2 emission variations obtained with different biofuel blends tested at INRETS on current passenger cars are compared with the emission models proposed by the ADEME working group and the JEC one dealing with LCA analyses. Small but significant CO2 reductions are observed over realistic driving cycles with blends containing as little as 5 to 10% biofuel by volume. These reductions are underestimated by emission models used in JEC and EMPA tank-to-wheel analyses.
GHG balance for light vehicles fuelled with different biofuel blends