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Biobutanol: The Next Big Biofuel?

It’s touted as a superior renewable fuel but challenges have stymied the industrial-scale production of biobutanol. Now, however, Dupont and BP have teamed to develop and commercialize the fuel. This comes as scientists announce advancements in the design of process technologies and the engineering of microbes aimed at improving the economics of mass-producing biobutanol.

By Jessica Ebert

It’s certainly not new to the renewable fuel scene. In fact, some experts would say that, historically, the fermentation of sugar-based feedstocks into butanol takes a back seat in importance to ethanol. Biobutanol plants operated in numerous countries, including the United States, UK, China, Russia, South Africa and India, during the first two World Wars.

These plants were designed to harness the fermenting talents of microbes to produce acetone from feedstocks such as molasses and corn starch. The acetone was used to make a smokeless gun powder and a propellant for rockets. Interestingly, acetone was not the only product of this fermentation. Ethanol was produced in small amounts but the major product of the fermentation was butanol.

Starting in the 1960s, the growth of the petroleum industry and the cheaper cost of producing butanol from petroleum products rather than renewable feedstocks made the biobased butanol plant obsolete. The last significant vestige of the industry—a facility in South Africa—ceased its operations in the early 1980s. But rising oil prices and concerns surrounding climate change and national security have rejuvenated interest, research and development into biobutanol. Although the primary use for the alcohol is as an industrial solvent, it offers several advantages over ethanol as a transportation fuel. Since the molecule contains four carbons compared with the two of ethanol, those extra chemical bonds release more energy when burned. In addition, butanol is less volatile than ethanol, it can be used at a 100 percent blend in internal combustion engines without any modifications, it doesn’t attract water like ethanol so it can be transported in existing pipelines and it is less sensitive to colder temperatures. “Butanol is an excellent fuel,” says Nasib Qureshi, a chemical engineer with the USDA Agricultural Research Service in Peoria, Ill. “As a result of gas prices going up it is looking more effective than ethanol and more effective than gasoline.”

Some big names in the energy business seem to agree. In 2006, BP and DuPont announced a joint venture to deliver advanced biofuels, initially targetting biobutanol. This past spring, the companies announced results from fuel testing including: that a 16 percent biobutanol blend performs similarly to a 10 percent ethanol blend and higher biobutanol blends also produce favorable results; that the energy density of biobutanol is closer to unleaded gasoline; and that biobutanol does not phase separate in the presence of water. “Biobutanol addresses market demand for fuels that can be produced from domestic renewable resources in high volume and at a reasonable cost; fuels that can be used in existing vehicles and existing infrastructure; fuels that offer good value to consumers; and fuels that meet the evolving demands of vehicles,” says Frank Gerry, BP Biofuels program manager.

Earlier this year, the companies announced that the partnership was developing biocatalysts for the production of 1-butanol as well as 2-butanol. (The latter is called an isomer of butanol because although it contains four carbons, the atoms of the alcohol are arranged differently). The goal of the partnership is to deliver a biobutanol production process with economics equal to ethanol production by 2010. Currently, the two companies have applied for more than 60 patents in the

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