Half our electricity comes from incinerating coal that we strip from the ground. The rest comes from burning oil and methane, or from damming rivers or splitting uranium (and leaving behind waste that stays dangerous for 10,000 years). Of the common renewables, solar is costly, and wind is geographically limited. Hydrogen, the pundits say, is the fuel of the future; it converts cleanly to electricity with water as the sole byproduct. But how should we produce this valuable gas? Today, industrial producers strip it from natural gas, a finite resource, in a process that generates greenhouse gases. Berkeley professor Tasios Melis thinks he has a better idea. In 1998, the biochemist found that starving green algae of the nutrient sulfur causes the tiny plants to alter their photosynthetic pathways to pump out pure hydrogen. He patented the process in 2000, and last year launched a startup called Melis Energy in hopes of licensing it to energy producers. It'll take further research to make the algae commercially viable, but if Melis succeeds in securing adequate R&D funds -- $10 million to start -- he and his CEO, Steve Kurtzer, expect their little green biomachines to hit the market within two to five years. Perhaps one day soon, we'll be pulling into filling stations and telling the attendant: "Fill 'er up with swamp gas."