October 31st, 2008 · No Comments

By John DeFore
Green Right Now

In the quest to ween cars and trucks off oil, alternative-fuel schemes may be heading for a roadblock they haven’t fully considered: water.

Public discussions of alternative fuels have rarely if ever touched on how much water might be needed to

produce such fuel on a large scale. But researchers in Texas warn that it may be much more than you’d expect.

Their study, published in the latest issue of Environmental Science & Technology analyzed two kinds of water usage: water that is withdrawn (”water that is taken from a surface water or groundwater source, used in a process, and given back from whence it came”) and that which is consumed (”taken from surface water or groundwater source and not directly returned”).

They compared fossil-fuel use to hydrogen, electricity, and two biofuels to find how much water was used per gallon traveled, and came to a discouraging conclusion: “Fuels more directly derived from fossil fuels are less water intensive than those derived either indirectly from fossil fuels (e.g., through electricity generation) or directly from biomass.” In fact, hydrogen and electric cars in their study that relied on the U.S. grid “withdraw five to 20 times and consume nearly two to five times more water” than cars running on gasoline.

Some alternative fuels did perform comparably to conventional ones, though: biofuels that were produced without irrigation, hydrogen derived from methane, and electricity produced by certain renewable means that don’t involve steam.

The study’s authors Carey W. King and Michael E. Webber are with the Jackson School of Geosciences at the University of Texas at Austin.

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