Hence the move among American carmakers to concentrate instead on more familiar stopgap technologies. The current favourite is the "flex- fuel" vehicle that can run on either E85 (85 per cent ethanol and 15 per cent gasoline) or straight gasoline. You can see why. The Energy Policy Act of 2005 requires 7.5 billion U.S. gallons of biofuel be blended into gas by 2012.

For many drivers, that something better is cellulosic ethanol -- an alcohol made from straw, leaves, stalks, cane or, best of all, switchgrass, a hardy perennial that grows prolifically almost anywhere. Unlike most other forms of biomass, switchgrass uses the more efficient C4 fixation process to bind carbon dioxide from the air to form its ethanol-producing sugars.

Being a perennial, farmers don't have to reseed switchgrass after harvesting it. In "well-to-wheels" studies, ethanol made from switchgrass delivers 540 per cent more energy than it consumes during growth, harvesting and manufacture. As a bonus, switchgrass ethanol emits significantly fewer greenhouse gases than corn-based ethanol.