Is slime the next energy frontier? With the price of oil edging above $140 a barrel this summer, and corn ethanol under attack for its influence on food prices and its negligible impact on global warming, algae is being touted as a next-generation renewable fuel source.

Algae's advantages begin with its three ingredients: sun, water, and CO2. Unlike ethanol, whose production relies on conventional fuel, algae is fueled by a combination of photosynthesis and water -- pure, nonpotable, or brackish -- meaning it can thrive in areas unsuited to agriculture. Moreover, while corn has an annual yield per acre of between 60 gallons and 300 gallons of biofuel, algae can yield upward of 5,000 gallons, in part because biofuel can account for as much  as 30 percent of its biomass.

The production process is still in its early stages, and much of the technology remains either experimental or first generation. But a few commercial-scale operations are set to go online in 2008, and a new trade association, the Algal Biomass Organization, was formed in May. One company, Sapphire Energy, has even had its "green crude" certified at a 91-octane rating. While not yet fully carbon-neutral, it isn't bad for a bucket of slime.