A company called Environmental Power is building the country's largest facility for converting cow manure into natural gas. The company is constructing eight enormous tanks outside Stephensville, Texas, that will each be able to hold 916,000 gallons of manure. The plan: Add high-carb materials, cook to above 130 degrees Fahrenheit, and let the bacteria start converting all that refuse into methane. There's a great, detailed piece on the company's plans for turning poop into profit on Xconomy.—Gregory Mone

We've been burning "biomass" since the Paleolithic era, when wood fires warmed the cave and slow-roasted the leg of mastodon. Today most biomass energy still comes from wood, but we're perfecting new ways to produce electri-city from agricultural waste, grassy plantseven sewage.