As he leads a tour of the labs at Coskata, a startup based in Warrenville, IL, Richard Tobey, the company's vice president of research and development, pauses in front of a pair of clear plastic tubes packed with bundles of white fibers. The tubes are the core of a bioreactor, which is itself the heart of a new tech­nology that Coskata claims can make etha­nol out of wood chips, household garbage, grass, and old tires--indeed, just about any organic material. The bioreactor, Tobey explains, allows the company to combine thermochemical and biological approaches to synthesizing ethanol. Taking advantage of both, he says, makes Coskata's process cheaper and more versatile than either the technologies widely used today to make ethanol from corn or the experimental processes designed to work with sources other than corn.

Tobey's tour begins at the far end of the laboratory in two small rooms full of pipes, throbbing pumps, and pressurized tanks--all used to process synthesis gas (also known as syngas), a mixture of carbon dioxide, carbon monoxide, and hydrogen. This is the thermo­chemical part of Coskata's process: in a well-known technique called gasi­­fication, a series of chemical reactions carried out at high temperatures can produce syngas from almost any organic material. Ordi­narily, chemical catalysts are then used to convert the syngas into a mixture of alcohols that includes ethanol. But making such a mixture is intrinsically inefficient: the carbon, hydrogen, and oxygen that go into the other alcohols could, in principle, have gone into ethanol instead. So this is where Coskata turns from chemistry to biology, using microbes to convert the syngas to ethanol more efficiently.