BusinessWeek: It’s a bold vision: Replace billions of gallons of gasoline not with ethanol from corn or other food crops but with biofuels made from plants, such as prairie grass in Tennessee pastures or algae percolating in Florida. Such a move would slash dependence on oil, create thousands of jobs, and reduce emissions that contribute to global warming. In the U.S., the idea has powerful political support. Congress has decreed that the country must be using 21 billion gallons of “advanced” biofuels a …