Potentiality of ethanol as a fuel for dedicated engine

One of the major challenges of the automotive industry is to reduce the greenhouse gases, and especially CO2 emissions. Many research programs are currently being led on this subject, aiming at reducing the fuel consumption of vehicles, but also at optimizing the fuel composition. The overall process must indeed be taken into account, from the fuel production to the vehicle emissions, and a "well to wheel" balance has to be calculated for each technology. Ethanol seems to have important assets to comply with these new constraints: it is extracted from the biomass and consequently has a good "well to tank" CO2 emission balance. Moreover, its properties, especially in terms of octane number and latent heat of vaporization allow a large improvement of the engine. The present paper aims at taking stock of the ethanol path. The main production ways are tackled, especially concerning their energy balances. The main advantages and drawbacks of the use of such a fuel are then summarized. Finally, an example of the gains that can be obtained by an optimization of the engine using pure ethanol is presented. A small supercharged engine has already been modified to benefit from the potential of ethanol, especially in terms of knock resistance. The performances of this engine have been compared with those of the initial gasoline engine, showing that important gains can be obtained with such a technology.