Are Switchgrass' Days Numbered?
Move over, switchgrass: there are some new grasses in town gunning for your biofuel crown. Researchers at the University of Northern Iowa's Tallgrass Prairie Center (TPC) are looking at ways to use the state's mixed prairie plantings as a source of renewable energy — as biomass to produce ethanol or to burn for electricity. "When you hear about biomass, you usually hear only about switchgrass, but we're looking at using prairie plants including wildflowers," said Dave Williams, manager of TPC's Prairie Institute.
A study conducted this past year by David Tilman, an ecology professor at the University of Minnesota, had demonstrated the potential for polycultures of multiple grass, prairie and wildflower species to serve as an alternative to switchgrass in producing ethanol. Tilman and his colleagues found that, in addition to producing more than twice the biomass than single-species planting (not less than 238% more than switchgrass), multiple-species plantations restored biodiversity, grew on degraded land and — perhaps most importantly — could be carbon negative. Biofuels derived from this source could also store up to 51% more energy per acre than corn.Because Tilman's study was only conducted on small, hand-weeded parcels of land, researchers at the TPC plan on expanding its scope to make the results applicable to local farmers, who commonly use hundreds of acres. Daryl Smith, the director of the TPC, believes that using the multiple species plantings on sandy, marginal agricultural land could yield several benefits, not least of which would be reducing soil erosion and creating better habitats for wildlife.
The researchers are particularly interested in seeing how the prairie grass stands sustain harvest — in other words, if they will need to be burned down less or if certain parts of the stand will only need to be harvested every year in rotation. They will also convert the plantings into pellets and cubes to examine their potency as a new source of fuel. The TPC will collaborate with Cedar Falls Utilities (CFU) to test how much electricity could be generated by burning large amounts of the biomass.
Smith estimates that 100 acres of the mixed prairie plantings could provide enough fuel for an 8-hour test burn at one of CFU's facilities. Bill Dotzler, a state senator who helped the TPC gain the necessary initial funding, is hopeful about their potential: "You almost get a trifecta with this --- you clean the streams, you provide habitat for pheasants and other wildlife and you produce an alternative fuel ... It's not going to be the whole answer, but I think burning the native plants could be an important part of the whole puzzle."