Energy How Coskata Makes Biofuels A versatile new process for making biofuels could slash their cost. by Kevin Bullis February 19, 2008 Sponsored by In the version of the reactor that’s currently in operation, water flows around thin fibers coated with colonies of bacteria. Since the fibers shown here are hollow, they can deliver gases that feed the bacteria. The bacteria convert these gases into ethanol, which flows out of the bioreactor mixed with water. The water is removed to yield fuel-grade ethanol that’s 99.7 percent pure. Coskata’s ethanol-producing bacteria can’t breathe oxygen, so researchers working to improve them use sealed, atmosphere-controlled hoods shown here. Getting the most from the bacteria means optimizing the nutrition they receive. So the researchers grow the bacteria in a suspended culture (large flasks) and feed them different mixes of nutrients (small bottles with red caps) to determine which combinations result in the highest levels of ethanol production.