The fuels blends considered in the present article include E5, E10, and E85. The LHV, density, and biogenic carbon content of ethanol are taken as 26.8 MJ/kg, 0.790 kg/l, and

0. 520 kg C/kg. The LHV, density, and fossil carbon content of ethanol are taken as

42.5 MJ/kg, 0.750 kg/l, and 0.865 kg C/kg. The characteristics of the fuels blends are calcu­lated according to the respective volume shares of ethanol and gasoline. The effect of consid­ering different fuel blends and/or other hypotheses regarding fuel performance is investigated in the case study section.

As discussed previously, the performance of bioethanol as a vehicle fuel strongly depends on its rate of incorporation into gasoline. Indeed, although bioethanol shows a significantly lower LHV compared with gasoline (which leads to expect an increase in vehicle fuel con­sumption when ethanol is added to gasoline), many vehicle tests in the European context (AEAT, 2002; EMPA, 2002,2007b; IDIADA, 2003) have demonstrated the improved efficiency (expressed in MJth/km) of gasoline-ethanol blends with respect to standard gasoline (Table 2). In 100% of the tests reported in these studies, gasoline-ethanol blends indeed show an improved efficiency (in MJth/km) compared with standard gasoline. On average, energy consumption per km is reduced by 2.7%, 7.5%, and 2.5% with E5, E10, and E85, respectively.

All these data, however, refer to fuel blends rather than ethanol specifically. In order to evaluate the WtW net GHG emissions of ethanol, it is necessary to define the fuel efficiency of the ethanol component in fuel blends. This is done in this chapter by assuming that the fuel efficiency (in km/MJth) of the gasoline component in fuel blends is equal to that of standard gasoline on its own, and that the difference is entirely explained by the presence of bioethanol in the fuel blend. If we assume an average fuel consumption of 2.564 MJth/km for gasoline (as reported in ecoinvent), the specific fuel consumption of ethanol (in MJth/km) is calculated according to the data in Table 2. The results are reported in Table 3.