Lester Brown, founder of the Earth Policy Institute, said the major auto manufacturers' focus on flex-fuel vehicles that use corn-based ethanol instead of electric cars is the wrong strategy.
"I think it's based on the idea that we're going to be able to produce huge amounts of crop-based motor fuel," he said. "I'm not sure we can."
World production of ethanol in 2005 was estimated at 12.2 billion gallons, according to the Renewable Fuels Association, a national trade group. The U.S. was the world leader, producing 4.26 billion gallons, followed by Brazil with 4.23 billion gallons, the group said.