Researchers from the University of Texas at Austin (United States) recently reported the use of a “Water Intensity” index, to compare/assess water consumption and withdrawal during the production and use of conventional and alternative fuels. They defined the water intensity index as “water usage per mile driven” (in the units, gallons water/mile). Their results showed that the lowest levels of water intensity (less than 0.15 gal/mile for water consumption and 1 gal/mile water withdrawal) were for light duty vehicles (LDV’s) using: (1) conventional petroleum-based gasoline/diesel, (2) non-irrigated biofuels, (3) hydrogen derived from methane or electrolysis via non-thermal renewable electricity, (4) electricity from non-thermal renewable energy resources. Biofuels from irrigated feedstocks in the United States were found to have relatively high values for LDV water intensities. For corn ethanol, water consumption and water withdrawal intensities were 28 gal/mile and 36 gal/mile, respectively. For soybean biodiesel, the water consumption and withdrawal intensities were 8 gal/mile and 10 gal/mile, respectively. Countries with limited water resources may need to carefully map out their own national biofuel policies considering the potential impacts of alternative fuels on water use. The full results are published in the September 2008 issue of the Environmental Science and Technology journal (URL above)..