Diverse mixtures of prairie plant species are the best biomass source for producing bio-based fuel to replace petroleum, a new study has revealed.
Led by David Tilman, a University of Minnesota ecologist, the study shows that mixtures of native perennial grasses and other flowering plants provide more usable energy per acre than corn grain ethanol or soybean biodiesel and are far better for the envi-ronment.
“Biofuels made from high-diversity mixtures of prairie plants can reduce global warming by removing carbon dioxide from the atmosphere,” says Tilman. “Even when grown on infertile soils, they can provide a substantial portion of global energy needs, and leave fertile land for food production.”
Based on 10 years of research at the university’s Cedar Creek Natural History Area, the study shows that mixtures of native prairie species produce 238% more bioenergy, on average, than the same marginal land planted to single prairie plant species, including switchgrass.
“Switchgrass is very productive when it’s grown like corn in fertile soil with lots of fertilizer, pesticide and energy inputs,” says Jason Hill, a postdoctoral researcher involved in the study. “But this approach doesn’t yield as much energy gain as mixed species in poor soil, nor does it have the same environmental benefits.”
Tilman says fuels made from prairie biomass are carbon negative, which means that producing and using them reduces the amount of carbon dioxide in the atmosphere. In contrast, corn ethanol and soybean biodiesel add carbon dioxide to the atmos-phere, although less than fossil fuels.
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