Ferris references a study released by the U.S. Department of Energy in June of this year that concluded that corn ethanol yields 2.3 BTUs of energy for every BTU used to grow it. It turns out that the calculation in this study added in a factor for the reuse of the waste materials from ethanol production. The distillers' dried grain that is left over from the milling and fermentation process is now commonly being incorporated into livestock feed in place of raw corn grain and high protein meal. Since feedstocks that have already been grown are replacing the need to grow more, there is a net positive change in the energy balance.
Unfortunately, the DOE's calculation still doesn't account for water use in growing and processing the corn and this may actually be a bigger problem than the energy use. Until cellulosic ethanol production is widely commercialized, the overall cost-benefit ratio of biofuels is likely to remain vague.
[Source: Lansing State Journal]