Genomic Science Program

Potential Biofeedstock: Switchgrass

Switchgrass. Photo Courtesy NREL.

Switchgrass is a perennial prairie grass that is native to all of the United States, except California and the Pacific Northwest. Typically, it grows 3 to 5 feet tall, but it can grow as high as 10 feet or more in southern parts of the United States. Its deep root system extends nearly as far below ground as the plant does above ground.

This grass species has one of the highest potentials for use as a biofuel feedstock crop mainly because it can tolerate almost any soil type and it grows well under a wide range of climatic conditions from floods to droughts. Upland switchgrass ecotypes are shorter, fine stemmed, and more adapted to drier habitats, whereas the more coarse-stemmed lowland ecotypes grow taller and in bunches on wetter, marshy sites.

As an indigenous species, switchgrass is resistant to many pests and plant diseases, and its C₄ photosynthetic pathway enables it to produce high lignocellulosic biomass yields with very low amounts of chemical inputs. Yields range from 7 to 16 tons/acre in the Southeast, to 5 to 6 tons in the western Corn Belt, to 1 to 4 tons in North Dakota. As much as 96 gallons of ethanol can be produced from each ton of dry switchgrass. Once established in the field, switchgrass can be harvested with conventional haying equipment, either annually or semiannually, for 10 or more years before replanting is needed.

Switchgrass offers a number of other environmental benefits in addition to its potential use as a biofuel. Like other plants, switchgrass removes CO₂ from the atmosphere by incorporating it into plant tissue, both above and below ground. Requiring no annual tillage, switchgrass also can slow runoff and anchor soils, helping to prevent erosion. It also provides habitat for pheasants, ducks, and other wildlife.

Cautionary note: Switchgrass can spread aggressively and without proper management may become weedy or invasive in some regions or habitats.

References
“Biofuels from Switchgrass: Greener Energy Pastures,” Oak Ridge National Laboratory.

Bransby, David. Switchgrass Profile. Oak Ridge National Laboratory.

Comis, Don. “Switching to Switchgrass Makes Sense,” Agricultural Research, July 2006, U.S. Department of Agriculture, Agricultural Research Service.

Lewandowski, Iris, et al. “The Development and Current Status of Perennial Rhizomatous Grasses as Energy Crops in the US and Europe,” Biomass and Bioenergy, 25 (2003), 335–361.

Plant Fact Sheet, U.S. Department of Agriculture, Agricultural Research Service.

Rinehart, Lee. “Switchgrass as a Bioenergy Crop,” ATTRA-National Sustainable Agriculture Information Service.