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with no input of fertilizer, no irrigation, no input of pesticides, almost no energy input at all," says Tilman. With low energy inputs, cellulosic ethanol might produce four times more energy than the fossil fuel it consumes.
• With little need for fertilizer or pesticides, native grass production produces little polluted runoff. Since the soil is never bare or plowed, little erosion occurs. According to University of Minnesota soil scientist Gyles Randall (B.S. '63, M.S. '72), nitrogen losses from land planted with perennial grasses are only 2 to 3 percent of the losses from corn and soybean fields. Loss of phosphorus and sediment are similarly low.
• Diverse grasslands, such as native prairie, produce 51 percent more energy per acre than corn, even though corn grain produces more ethanol per weight. After 10 years, diverse plots produced 238 percent more energy than monocultures, such as switchgrass. Multispecies plots are more resilient too. And Tilman's past research has shown that diverse grasslands outproduce monocultures during drought.
• Prairie grasses' massive root systems sequester carbon, actually reducing greenhouse gases in the atmosphere. Raising prairie grasses for biofuels would not only produce less greenhouse gas than burning fossil fuels, it would actually remove and store 1.2 to 1.8 tons of carbon dioxide per acre per year over the course of a century.
• The researchers estimate that growing mixed prairie grasses on all of the world's degraded land would produce enough bioenergy to replace 13 percent of global petroleum consumption and 19 percent of global electricity consumption.
Ultimately, says Hill, biomass could produce many fuels to power vehicles. Grasses or woody plants could be burned for electricity, such as to charge electric cars, or converted to synthetic fuels. "There are many technologies out there that can produce transportation fuels," he says. "Ethanol is just one of them."
Several cellulosic ethanol research plants already operate in the United States. Canada's Iogen runs a demonstration-scale plant in Ottawa to make cellulosic ethanol from wheat, oat, and barely straw. Ontario-based SunOpta is working with Abener Energia of Seville, Spain, to build a commercial demonstration plant in Spain that is scheduled to begin converting wheat stalks to ethanol in 2007. SunOpta has also supplied the technology for a similar sized plant in Jennings, Louisiana, to produce ethanol from the crushed fiber of sugar cane stalks. Xethanol, a U.S. company, is building a plant in Georgia to brew cellulosic ethanol from various industrial wastes, including waste wood products.
The National Energy Policy Act of 2005 provides several incentives to encourage cellulosic ethanol production, including grants, loan guarantees, research, and "credits" that give preference to production of cellulosic ethanol in meeting renewable energy targets, Tiffany explains. "Maybe that's enough for now, until the technology moves along," he says.
At the University of Minnesota, much of that research is being conducted under the Initiative for Renewable Energy and the Environment and has been instrumental in funding research, such as the biofuels study, on alternative energy sources. "We have to explore many different avenues for doing this," Hill says. "That would benefit our state, our nation, and not just the pockets of large energy companies."
Ultimately, it could benefit our environment. By generating fuel from prairies, says Hill, "you could both take off the biomass and have minimal disturbance to wildlife. . . . It could be that we could actually increase the wild habitat in our states. We would have something that would serve the aesthetic value, the sportsman, and the biofuels."
Greg Breining, St. Paul, writes about nature and the environment for several publications, including the New York Times, National Geographic Traveler, and Wildlife Conservation.
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