The potential is huge, but the transition to the much-ballyhooed hydrogen economy won't be easy. Pure hydrogen isn't a naturally occurring fuel, and today the cheapest way to make it is from oil or natural gas, which does nothing to offset CO2 emissions.

In presidential campaign of 2004, Bush and Kerry managed to find one piece of common ground: Both spoke glowingly of a future powered by fuel cells. Hydrogen would free us from our dependence on fossil fuels and would dramatically curb emissions of air pollutants, including carbon dioxide, the gas chiefly blamed for global warming. The entire worldwide energy market would evolve into a â€hydrogen economy†based on clean, abundant power. Auto manufacturers and environmentalists alike happily rode the bandwagon, pointing to hydrogen as the next big thing in U.S. energy policy.