Friday, November 5, 2010

Drop-in Fuels from Butanol



By Robin J. Johnson, Ph.D.

Despite a 55% drop in U.S. venture capital investment in the cleantech sector, new technologies in biofuels continue to appear on the horizon. One of these, drop-in fuels from biobutanol, has gained air time as players such as the U.S. Navy, and French oil giant TOTAL throw their support behind biobutanol development.

On November 3, 2010, Cobalt Technologies of California announced that it signed a Cooperative Research and Development Agreement (CRADA) with the U.S. Navy to develop jet and diesel fuels from biobutanol. Cobalt has developed a process for converting biomass to n-butanol (a butanol isoform) using a Clostridium bacterium that can metabolize both C5 and C6 sugars found in lignocellulosic materials. The technology for converting n-butanol (which has 4 carbons) to jet fuel (a mixture of hydrocarbons containing 6-16 carbons) and diesel fuel (a mixture of hydrocarbons containing 8-21 carbons) was developed by the U.S. Naval Air Warfare Center Weapons Division. Cobalt's biobutanol process employs a chemical process to extract sugars from biomass followed by continuous fermentation. Converting n-butanol to larger hydrocarbons involves a dehydration reaction that converts n-butanol to butene (a.k.a. butylene). Butene reacts with itself to form oligomers. Cobalt opened its pilot facility in Mountain View California in January of this year.

A similar story (though without the U.S. Navy support and with support from TOTAL) exists for a Colorado company, Gevo. Gevo produces isobutanol (another isoform of butanol) from sugar and grain crops using genetically modified yeast for the fermentation step. The company has demonstrated technology to convert isobutanol into aliphatic and aromatic hydrocarbons. Like Cobalt Technologies, Gevo's chemistry depends on an initial dehydration step where isobutanol is converted to isobutylene. Isobutylene can in turn be oligomerized to jet and diesel fuel blend stocks. In August of this year, Gevo filed a registration statement on form S-1 with the Securities and Exchange Commission for a proposed initial public offering of shares of its common stock. In September, the company acquired Agri-Energy's ethanol production plant in Luverne, MN in order to retrofit it for isobutanol production.

While many may decry the widespread use of biofuels in automobiles in the U.S., preferring development of electric cars, it is clear that certain modes of transport (airplanes, trucks, freight trains, freighters) will depend for quite some time upon the energy density contained in chemical bonds. It is for these applications that drop-in biofuels hold the most promise.

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