Give your car a drink, save the planet, and end dependence on foreign oil. That’s more or less the plan President George W. Bush unveiled during his State of the Union message earlier this week, in which he also declared his intention to “fund additional research in cutting-edge methods of producing ethanol, not just from corn, but from wood chips and stalks, or switch grass.” By throwing tax dollars at research on how to turn vegetation into alcohol to burn in our cars and trucks, Bush hopes to move the country “beyond a petroleum-based economy, and make our dependence on Middle Eastern oil a thing of the past.”

Currently, about 3.4 billion gallons of ethanol for fuel is produced from fermenting sugars and starches derived from corn. This ethanol is blended into gasoline in the United States and is equal to about 2 percent of all gasoline sold by volume and 1.3 percent of its energy content. The federal Energy Policy Act of 2005 requires that 7.5 billion gallons of renewable fuels be blended into gasoline by 2012 and the government offers a $0.51 per gallon of ethanol tax credit. A federal government study in 2005 envisioned biofuels replacing 30 percent of petroleum consumption by 2030.

The motivations behind the push for ethanol vary. For farmers and farm state politicians it’s another agriculture subsidy. For foreign policy hawks, it’s a way to free our country from dangerous dependence on unstable and hostile regimes. It’s also an answer to peak oilers who claim that the world is about to run out of fossil fuels. Environmentalists see ethanol as fuel that does not add more man-made heat-trapping gases to the atmosphere and thus helps curb global warming. But will producing alcohol to burn in internal combustion engines really save the planet and cut dependence on foreign oil? Maybe.

For years, scientists have been fighting over whether making ethanol from crops uses more energy than it produces. On negative side stand Cornell University ecologist David Pimentel and University of California-Berkeley environmental engineer Tad Patzek. They published a study last July that found that producing ethanol using crops used 29 to 57 percent more fossil fuel energy than it saved.

Last week, the Energy and Resources Group at UC-Berkeley headed by Alex Farrell published an analysis in Science of six energy balance studies on producing ethanol, including the Pimentel and Patzek study, and came to the opposite conclusion. The Berkeley team found that current methods of producing ethanol from crops, chiefly corn, generate about 20 percent more energy than they use. Farrell argues that the Pimentel and Patzek study included out-of-date information and did not count the co-products such as animal feed that result from ethanol production. Stay tuned