A new study at the University of Minnesota shows that a diverse mixture of native perennial grasses and other flowering plants provide far more usable energy per acre than corn grain ethanol or soybean biodiesel and offer additional environmental benefits.
The research was supported by the National Science Foundation and the University of Minnesota Initiative for Renewable Energy and the Environment.
The study concludes 10 years of research at Minnesota's Cedar Creek Natural History Area, one of 26 NSF long-term ecological research sites. It shows that degraded agricultural land planted with diverse mixtures of prairie grasses and other flowering plants produces 238 percent more bioenergy on average than the same land planted with various single prairie plant species, including switchgrass.
The study was led by David Tilman, a University of Minnesota ecologist. Tilman estimates that fuel made from this prairie biomass would yield 52 percent more energy than ethanol from corn grown on fertile land. Tilman said prairie plants require little energy to grow and all parts of the plant above ground are usable. Plants included grasses, forbs and legumes.
I can see great wildlife benefits from this approach, as well as higher water quality in lakes and streams.
Fuels made from prairie biomass are carbon negative, which means that producing and using them actually reduces the amount of carbon dioxide (greenhouse gases) released. By contrast, corn ethanol and soybean add carbon dioxide to the atmosphere - though less than fossil fuels.
Switchgrass was one of 16 species in the study, however researchers noted that when grown by itself in poor soil, it performed no better than other plants, and gave less than a third of the energy of the high diversity plots.
Jason Hill, a co-author of the study, said switchgrass is very productive when grown like corn in fertile soil, but requires lots of fertilizer, pesticides and energy inputs. It also doesn't provide as much energy gain as the diverse plants in poor soil, nor provide the same environmental benefits.
The researchers estimate growing mixed prairie grasses on all of the world's degraded land could produce enough bioenergy to replace 13 percent of global petroleum consumption and 19 percent of global energy consumption.
They concluded that the practice of using degraded land to grow mixed prairie grasses for biofuels could provide stable energy production as well as added benefits including renewed soil fertility, cleaner ground and surface waters - which could lead to preservation of wildlife habitats and increased recreational opportunities.
It is obvious more grass on the landscape is a better choice, though some segments of the agri-business industry will likely dispute the study's results. But ask yourself, who benefits most in the current rush to ethanol production? And who has the most to lose if there is a substitute crop that requires less energy input and can be grown on poor soil?
