By this spring, drivers in the U.K. will encounter an unfamiliar, and unprecedented, option at the pump: gasoline blended with a corn-based alcohol called butanol. It's part of a pilot project run by energy company BP, which aims to gauge public reaction to the new fuel. Butanol is easier to store and transport than existing biofuels and has an energy content more comparable to that of gasoline. Now, with more efficient ways to make it on the horizon, an increasing number of experts think butanol is poised to overtake ethanol as the best-selling alternative fuel on the market.