Champaign, Illinois – In the largest field trial of its kind in the U.S., researchers at the University of Illinois have determined that the giant perennial grass Miscanthus x giganteus outperforms current biofuel sources, including corn and switchgrass, by a large margin. The researchers reported that using Miscanthus as a feedstock for ethanol production in the U.S. could significantly reduce the acreage dedicated to biofuels while still meeting government production goals.
The report found that using corn or switchgrass to meet a current White House goal of offsetting 20 per cent of gasoline use would take 25 per cent of the current U.S. cropland out of food production. The same amount of ethanol derived from Miscanthus would only require 9.3 per cent of current agricultural acreage.
“What we’ve found with Miscanthus is that the amount of biomass generated each year would allow us to produce about two and a half times the amount of ethanol we can produce per acre of corn,” said crop sciences professor Stephen P. Long, who led the study. He said that in trials across Illinois, switchgrass produced only about as much ethanol feedstock per acre as corn. Like switchgrass, Miscanthus is a perennial that requires fewer chemical and mechanical inputs than corn, and is tolerant of poor soil quality.
“One reason why Miscanthus yields more biomass than corn is that it produces green leaves about six weeks earlier in the growing season,” Long said. The grass also stays green until late October in Illinois, while corn leaves wither at the end of August, he said. The growing season for switchgrass is comparable to that of Miscanthus, but it is not nearly as efficient at converting sunlight to biomass. “One of the criticisms of using any biomass as a biofuel source is (that) it has been claimed that plants are not very efficient, about 0.1 per cent efficiency of conversion of sunlight into biomass,” Long said. “What we show here is, on average, Miscanthus is in fact about one per cent efficient, so about one per cent of sunlight ends up as biomass. Keep in mind that when we consider our energy use, a few hours of solar energy falling on the earth are equal to all the energy that people use over a whole year, so you don’t really need that high an efficiency to be able to capture that in plant material and make use of it as a biofuel source.”
Because it is a sterile hybrid, Miscanthus must be propagated by planting underground stems, called rhizomes; mechanization allows the University’s team to plant about 15 acres a day. Once established, it returns annually without need for replanting. Its sterile form has not been found to be invasive in Europe or the U.S., Long said.