Current and Potential Future Performance of Ethanol Fuels

Ethanol is one of several alternative transportation fuels considered for replacement of conventional gasoline and diesel fuel. In the past, the net energy yield for ethanol production from corn or sugar crops has been less than favorable. Recent research on ethanol production from energy crops such as grasses and trees (biomass) has indicated a potential for very favorable net energy yields. Use of renewable biomass or lignocellulosic materials as feedstocks for ethanol production can decrease carbon dioxide emissions and significantly increase total production capacity potential by broadening the feedstock resource. New biomass processing technology for ethanol production has generated increased interest in ethanol as an alternative transportation fuel.

In this paper, the physical and chemical fuel properties of ethanol that affect spark ignition and compression ignition engine performance are evaluated through a search of the technical literature to determine the potential performance of this alternative fuel. Properties including energy density, heat of vaporization, flame temperature, ratio of product gases to reactants, specific energy, octane number, flammability limits, and flame speed are evaluated. Trends in automotive technology are also considered. Both empirical data of current performance and theoretical analyses of potential performance are presented with comparisons against conventional fuels. Projections of engine efficiencies are made for the years 2000 and 2010. Emission performance is also discussed.