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Spring/Summer 2009 Vol. 9 Number 1

Table of Contents

Fuel of the Future

Switchgrass, photo by Peggy Greb/USDA Agricultural Research Service

Driving the U.S. Toward Alternative Fuels

Transportation plays a key role in the U.S. economy and, as in most industrialized societies, it runs largely on petroleum-based fuels. The effects of this reliance on petroleum are broad, ranging from energy security to climate change. To reduce this state of dependence, alternatives are being developed. A new report from the National Research Council reviewed two: liquid fuels from coal and biomass.

Although corn-based ethanol is likely the most familiar form of biomass fuel, the report focused on biofuels from grass, waste, or forest debris, which can avoid the potential conflicts between food and fuel. Cellulosic ethanol, plant material converted into ethanol via bacteria or yeast, has become a center of attention in the U.S. transition to alternative fuels. In 2007, the U.S. Department of Energy offered up to $385 million in funding for projects that would bring cellulosic ethanol to market. The renewable fuel standards recently proposed by the U.S. Environmental Protection Agency require that transportation fuel in the U.S. contain 10.5 billion gallons of cellulosic biofuel by 2020.

Cellulosic ethanol is in the early stages of commercialization. Verenium, a biofuel company in the U.S., has a 1.4 million gallons per year demonstration plant running in Jennings, La., and recently announced plans to partner with oil giant BP to develop the first U.S. commercial-scale cellulosic ethanol plant. Plants such as these are a critical step in the transition to alternative fuel, according to the report. The know-how required to produce cellulosic biofuel, or any alternative fuel for that matter, will really only come from doing it.

Biobutanol production research at the Agricultural Research Service’s National Center for Agricultural Utilization Research in Peoria, Ill., photo by Peggy GrebAlthough cellulosic ethanol is moving forward, there are drawbacks to this form of fuel. Ethanol fuels are too corrosive to be distributed through gasoline pipelines; currently most ethanol here is distributed via railway or truck. This system works fine, as long as the ethanol market remains relatively small, but substantial investments in infrastructure would be needed to ramp up ethanol fuel use in the United States. The next generation of biofuels, such as biobutanol or other longer-chain alcohols, have chemical properties that would allow distribution in existing gasoline pipelines.

The report also looked at the possibility of producing transportation fuels from coal. One of the main benefits of coal is its abundance; it is estimated that U.S. coal reserves are sufficient to last at least 100 years, assuming that we maintain current rates of consumption. At the moment, the primary use for coal in the U.S. is power. If coal also became a source of transportation fuel, consumption rates could soar.

The environmental impact of coal-based fuel would be its most serious disadvantage. Coal mining would have to increase significantly in order to meet the demand for fuel, and carbon emissions from producing and using coal fuel would be nearly double that of petroleum. Geologic carbon storage would be necessary if coal-based fuels were to become a part of the U.S. transportation fuel portfolio.

One way to get both the environmental benefits of biofuel and the abundance and low cost of coal fuels, is to literally combine the two. A handful of pilot plants in Europe have begun mixing biomass with coal to produce fuel. Computer models suggest that the carbon emissions of combined coal and biomass would be similar to petroleum fuel and could be brought close to zero with geologic carbon storage.

Clearly, there is no magic solution to our petroleum addiction, but these approaches could reduce U.S. oil use by 15 percent to 25 percent and significantly reduce our dependency on foreign oil. All alternative fuels currently being discussed have both pluses and minuses; a future with alternative fuels will likely mean coming up with a number of approaches to expand the range of options for the U.S., and moving forward from there.  — Rebecca Alvania

 Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts. Panel on Alternative Liquid Transportation Fuels, Committee on America’s Energy Future, Phase 1, National Academy of Engineering and National Research Council (2009, approx. 300 pp.; ISBN 0-309-13712-8; available from the National Academies Press, tel. 1-800-624-6242; $49.95 plus $4.50 shipping for single copies.

The study was chaired by Mike Ramage, retired executive vice president of ExxonMobil Research and Engineering Co. The study was funded by the U.S. Department of Energy, BP America, Dow Chemical Company Foundation, Fred Kavli and the Kavli Foundation, GE Energy, General Motors Corp., Intel Corp., and the W.M. Keck Foundation.

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Copyright 2009 by the National Academy of Sciences