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PROBLEM: Can ethanol reduce oil imports without compromising food supplies? The Department of Energy's accelerated effort to develop a new generation of cellulosic ethanol provides a textbook example of the challenge posed by the collision of competing policy priorities. At ORNL's Bioenergy Science Center (BESC), a consortium of researchers is making progress toward the twin goals of reducing oil imports without compromising the world's supply of food.
While researchers pursue a variety of promising transportation technologies on the horizon, plant-based biofuels, like ethanol, have a more near-term potential to significantly reduce U.S. dependence on imported oil. However, when dramatic price spikes of gasoline temporarily increased demand for ethanol, many viewed ethanol, and the use of valuable farm land for the production of crops to make ethanol, as the cause of sharp world-wide increases in the cost of food. The perception remained despite several studies that suggested overall energy and petroleum costs, and not simply ethanol production, were the major causes of inflationary pressures on food prices. Faced with the need to protect world food supplies, the BESC is focusing on new ways of developing ethanol from biofeedstock crops such as switchgrass and poplar trees. The primary difference of this approach is that it does not use conventional ethanol-producing food crops such as corn, which contain large volumes of starch. This starch is easily broken down into sugar and then fermented to ethanol. In poplar and switchgrass, most of the sugar is contained in the cellulose that makes up stalks, stems and leaves. "Breaking starch down into sugars is a relatively easy process that occurs in our stomachs," says BESC scientist Brian Davison, "but cellulose is put together in such a way that only a very limited number of microbes can break it apart. Understanding the complex process of breaking cellulose into its component sugars is the fundamental challenge of the BESC research. Based upon about 18 months of progress, Davison is confident of gaining access to the cellulosic sugars. He believes the more important questions yet to be resolved are whether cellulosic biofuels can be produced economically and sustainably in sufficient volume to alter current consumption levels of gasoline. A competitive cost The price of oil fluctuated wildly, moving up and then back down three-fold during 2007-2008. Cellulosic ethanol is not competitive with oil priced at $30-50 per barrel. One of the BESC's goals is to find a way to convert cellulose to ethanol at less cost than gasoline—or at least be competitive enough for a marginal price difference, justified in terms of improved energy security and a reduction of fossil fuels emissions. Davison is convinced that the cost efficiencies needed to make cellulosic fuels economically viable are realistic. "We're not there yet," Davison says. "Despite the current deployment of cost of first-generation technology, the costs need to be reduced to make ethanol a large-scale industry. The creation of this second-generation technology is one of the main missions of the BESC." Davison notes that BESC has made rapid progress in the quest to identify highly productive plants and highly efficient microbes. Working in the National Renewable Energy Laboratory in Boulder, Colorado, BESC researchers have established a high-throughput screening process that has analyzed thousands of plant samples to see how much sugar is released when the samples are broken down by various microbial enzymes. "This process has shown that the natural variation in sugar release among poplar trees was greater than we expected," he says. "Our task now is to identify which genes allow higher levels of sugar release, so we can start eliminating and altering genes to maximize the process."
ORNL's team has made progress on the microbial side of the equation as well. According to BESC director Martin Keller, "Microbial strain development is coming along nicely. The center has a couple of different candidates at Oak Ridge and at our partner sites that show potential for consolidated bioprocessing." While some microorganisms consume biomass and others produce ethanol, the goal of consolidated bioprocessing is to identify or create an organism that does both in a single step. Such a discovery would save time and significantly decrease the cost of the ethanol production process. The center is now working with two groups of microbes capable of breaking down cellulose and fermenting the resulting sugars. "If the microbe can ferment the sugars, I'm confident we can genetically tweak the process to produce increasing volumes of ethanol," Davison says. "We know some of these organisms make ethanol—not as much as we want, and not just ethanol. However, if a microbe makes three or four things and we only want one, genetic engineering can produce the one we want." Despite his confidence, Davison notes that recently discovered organisms like the ones the BESC has been working with are often much more difficult to genetically engineer than microbes that have been studied for decades. "I am confident we can get the results we want," he says, "but I would hedge on how long it will take. We still need to understand how these microbes simultaneously undertake this enzyme production, degradation and fermentation in a single package." The potential impact The most convincing evidence that cellulosic ethanol has the potential to make a significant impact on the nation's transportation energy supply comes from the landmark "Billion Ton Study," produced in 2005 by researchers from ORNL's Environmental Sciences Division and the U.S. Department of Agriculture. The study's conclusion—that in the United States "significant amounts of land could shift to the production of perennial crops if a large market for bioenergy and bio-based products emerges without impacting baseline projections for food and feed demands,"—had a transformative effect on both U.S. energy policy and the willingness of industrial partners to invest in emerging ethanol technologies. A sustainable strategy Davison expects cellulosic ethanol to be a sustainable option but cautions that researchers first need to address issues such as soil fertility, which crops work best, and preferred agricultural practices. Fortunately, both switchgrass and poplar are well-suited to a range of climate conditions and soil types. Neither requires a great deal of water, and both can be grown on "marginal" land that normally would not be used to grow food crops. Research on poplar and switchgrass at ORNL has demonstrated that these perennials are actually better for the soil than food crops. "In some cases," Davison says, "they are even better for the land than letting it lie fallow because they store more carbon in the soil." Still, there are critics who will argue that, until scientists can disprove with certainty the potential of detrimental side effects, the appropriate policy is to do nothing. In the absence of an alternative proposal, Davison contends we cannot continue on the current path indefinitely, so we must do something better. BESC is now fully operational and funds more than 300 scientists working in locations around the country to develop sustainable energy alternatives. "Research is progressing extremely well in all areas," Keller says. "We have developed a multi-disciplinary partnership among national laboratories, academia, and industrial partners." This broad-based arrangement has enabled the center to draw on the strengths of each organization to advance new concepts and new strategies dedicated to finding solutions to one of America's most important scientific challenges. With growing confidence, they believe they can unlock the code to one way of meeting America's energy needs without compromising the environment or the world's increasing precious supply of food. |
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