As a biofuel, ethanol is relatively easy to make, but it has a lower energy density than gasoline and can’t be transported through existing pipelines designed for petroleum fuels. Isobutanol, however, can be sent through these pipelines, and its energy density is close to that of gasoline. It can also be turned into jet fuel, and it can be used as a raw material for the manufacture of plastics and many other chemicals normally derived from petroleum.
Both ethanol and isobutanol are made from sugars produced by breaking down biomass. But it’s not easy to produce isobutanol with the help of microbes like the ones that ferment those sugars into ethanol. So Peter Meinhold rewired the yeast genome, replacing genes that controlled ethanol fermentation with genes for a enzymatic pathway that would produce isobutanol. He cofounded Gevo in 2005 to commercialize the technology and produce isobutanol that would be cost-competitive with petroleum-based fuels.
Gevo has also enhanced the isobutanol-producing capacity of its yeast by developing a system that continously removes isobutanol as it is produced. (Otherwise, high concentrations of isobutanol would inhibit the growth of the yeast.) The company is also developing new versions of the yeast that can feed on sugars produced from grasses and wood chips. In 2009, Gevo announced the startup of a million-gallon-per-year demonstration facility retrofitted into an ethanol plant. The company has set a goal of going to market by 2012. –Nidhi Subbaraman