Biofuels from Switchgrass: Greener Energy Pastures |
| Test plots of switchgrass at Auburn University have produced up to 15 tons of dry biomass per acre, and five- year yields average 11.5 tons—enough to make 1,150 gallons of ethanol per acre each year. |
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The U.S. Department of Energy (DOE) believes that biofuels—made from crops of native grasses, such as fast- growing switchgrass—could reduce the nation's dependence on foreign oil, curb emissions of the "greenhouse gas" carbon dioxide, and strengthen America's farm economy. The Biofuels Feedstock Development Program (BFDP) at DOE's Oak Ridge National Laboratory (ORNL), has assembled a team of scientists ranging from economists and energy analysts to plant physiologists and geneticists to lay the groundwork for this new source of renewable energy. Included are researchers at universities, other national laboratories, and agricultural research stations around the nation. Their goal, according to ORNL physiologist Sandy McLaughlin, who leads the switchgrass research effort, is nothing short of building the foundation for a biofuels industry that will make and market ethanol and other biofuels from switchgrass and at prices competitive with fossil fuels such as gasoline and diesel. |
Switchgrass can be cut and baled with standard farming equipment. |
Many farmers already grow switchgrass, either as forage for livestock or as a ground cover, to control erosion. Cultivating switchgrass as an energy crop instead would require only minor changes in how it's managed and when it's harvested. Switchgrass can be cut and baled with conventional mowers and balers. And it's a hardy, adaptable perennial, so once it's established in a field, it can be harvested as a cash crop, either annually or semiannually, for 10 years or more before replanting is needed. And because it has multiple uses—as an ethanol feedstock, as forage, as ground cover—a farmer who plants switchgrass can be confident knowing that a switchgrass crop will be put to good use. |
And with recent advances in the technology of gasification, switchgrass could yield a variety of useful fuels—synthetic gasoline and diesel fuel, methanol, methane gas, even hydrogen—as well as chemical by-products useful for making fertilizers, solvents, and plastics. |
Besides helping slow runoff and anchor soil, switchgrass can also filter runoff from fields planted with traditional row crops. Buffer strips of switchgrass, planted along streambanks and around wetlands, could remove soil particles, pesticides, and fertilizer residues from surface water before it reaches groundwater or streams—and could also provide energy. |
And because switchgrass removes carbon dioxide (CO2 ) from the air as it grows, it has the potential to slow the buildup of this greenhouse gas in Earth's atmosphere. Unlike fossil fuels, which simply release more and more of the CO2 that's been in geologic storage for millions of years, energy crops of switchgrass "recycle" CO2 over and over again, with each year's cycle of growth and use. |
Looking down the road, McLaughlin believes switchgrass offers important advantages as an energy crop. "Producing ethanol from corn requires almost as much energy to produce as it yields," he explains, "while ethanol from switchgrass can produce about five times more energy than you put in. When you factor in the energy required to make tractors, transport farm equipment, plant and harvest, and so on, the net energy output of switchgrass is about 20 times better than corn's." Switchgrass also does a far better job of protecting soil, virtually eliminating erosion. And it removes considerably more CO2 from the air, packing it away in soils and roots. |
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