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Researchers, companies pursue biobutanol

By Jerry W. Kram
Biobutanol may be a promising alternative fuel, but it has been plagued with difficulties as organisms that produce butanol through fermentation are difficult to maintain and tend to have a low conversion efficiency. However, butanol has many properties that make it desirable as a biofuel, including a higher energy content than ethanol and good blending characteristics with conventional fuels, so it continues to attract research and corporate interest.

Green Biologics Ltd. operates a 300-liter-per-batch pilot plant in England. The company is joining with Mumbai, India-based Laxmi Organic Industries to build a commercial-scale biobutanol plant in India. The plant will produce 1,000 metric tons of butanol per year and is expected to begin production in 2010. The facility will use sugarcane as a feedstock, and will use a combination of thermophilic organisms and thermostable enzymes to break the biomass down into butanol.

Cobalt Biofuels in Mountain View, Calif., has raised $25 million in equity to continue pursuing its goal of commercializing biobutanol production. Investors included Cobalt's existing institutional investors Pinnacle Ventures, VantagePoint Venture Partners, The Malaysian Life Sciences Capital Fund and @Ventures, along with new players Life Sciences Partners and
Harris & Harris Group. Fouad Azzam, general partner of Life Sciences Partners, will be joining the Cobalt board of directors. The company's fermentation process uses continuous fermentation to maintain peak production rates for extended periods of time. It has patented a fluid separation technology, known as vapor compression distillation, that removes alcohol from the fermentation steep using approximately one-half the energy required in typical separation techniques.

As commercial activity moves forward, research continues in government labs for ways to make butanol production more competitive with existing fuels. Nasib Qureshi is working at the National Center for Agricultural Utilization Research in Peoria, Ill., on ways to convert wheat straw into biobutanol. Normally, fermenting biomass such as wheat straw involves four preparatory steps: pretreatment, hydrolysis, fermentation and recovery. These steps need to be carried out separately and sequentially, and Qureshi's lab was able to combine three of the four steps. He found a way to use the enzymes that hydrolyze the wheat straw while simultaneously letting the bacteria conduct the fermentation. The lab also devised a process called gas stripping, which removes the biobutanol continually as it's produced. Early trials of the process doubled productivity over traditional glucose-based fermentation, and also produced acetone and ethanol. If the process can be scaled to commercial production, it's estimated that 99 gallons of the three chemicals could be made from one ton of wheat straw.
 

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