Biobutanol

Biobutanol is an emerging biofuel; it is a 4-carbon alcohol (butyl alcohol) produced from the same feedstocks as ethanol including corn, sugar beets, and other biomass feedstocks. Butanol is generally used as an industrial solvent in products such as lacquers and enamels, but it also can be blended with gasoline for use in conventional vehicles. While there are four isomers of butanol, the most active biobutanol organizations are producing isobutanol for blending with gasoline. Biobutanol qualifies under the RFS, and which category it falls under depends on the feedstock used to produce it.

There are two Clean Air Act provisions that allow blending of biobutanol with gasoline—the substantially similar rule allows biobutanol blending up to 12.5%; and under the Octamix waiver, with human health affects testing, a 16% biobutanol blend is a legal fuel equivalent to E10. Biobutanol has an ASTM D7862 fuel quality standard for blends up to 12.5% with gasoline. It is important to ensure that biobutanol blended with ethanol gasoline combinations does not result in an oxygen content exceeding the U.S. Environmental Protection Agency (EPA) limit of 3.7%.

Oak Ridge National Laboratory has researched the compatibility of refueling equipment materials with biobutanol and found that equipment compatible with ethanol blends would also be compatible with biobutanol. Underwriters Laboratories (UL) announced in late 2013 that equipment certified under testing subject 87A (for blends above E10) could also retain certification if used with biobutanol. It is anticipated that biobutanol would be distributed by tanker truck and rail, with the potential for transportation in pipelines upon research demonstrating its safety.

Production

Producing biobutanol via fermentation has been possible since the early 1900s but is currently more expensive than producing petrochemicals. Modern butanol is produced almost entirely from petroleum. Renewed interest in biobutanol as a sustainable vehicle fuel has spurred technological advances to ferment biobutanol. The first biobutanol plants are retrofits of existing corn ethanol plants. Biobutanol companies produce a range of products, including transportation fuel with a goal of improving economic performance through diversification of product offerings. These products include solvents/coatings, plastics, and fibers. A challenge for biobutanol is that more ethanol can be produced from a bushel of corn than biobutanol.

Benefits

Biobutanol is an alternative to conventional transportation fuels. The benefits of biobutanol include:

  • Higher Energy Content—Biobutanol's energy density is 10%–20% lower than gasoline's (compared to ethanol (E100), which has an energy density 60% lower than gasoline), which makes its energy content relatively high among gasoline alternatives.

  • Lower Reid Vapor Pressure—When compared with ethanol, biobutanol has a lower vapor pressure, which means lower volatility and evaporative emissions.

  • Increased Energy Security—Biobutanol can be produced domestically from a variety of feedstocks, while creating U.S. jobs.

  • Fewer Emissions—Carbon dioxide captured by growing feedstocks reduces overall greenhouse gas emissions by balancing carbon dioxide released from burning biobutanol.

Research and Development

The U.S. Department of Agriculture's (USDA) Agricultural Research Service is studying biobutanol production. The U.S. Department of Energy (DOE) and the EPA are funding biobutanol research and development as part of their Small Business Technology Transfer and Small Business Innovation Research programs.

Companies involved in biobutanol production include Dupont and BP, and Gevo.

More Information

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