Picture the vibrant wildflowers and swaying grasses of prairies covering the Midwestern United States once again, teeming with wildlife and requiring very little management from people, yet providing a renewable energy sources.
Managing native grasslands for biofuel production provides more habitat for birds and other wildlife than growing corn for ethanol production. Not only do mixed species of grasslands provide superior habitat they may also be more efficient at producing energy than corn, soy, and other biofuel sources.
A recent study looked at bird populations in biofuel fields. The largest populations and greatest diversity of birds were found in a mixed-species grassland, nearly double the numbers found in corn fields, according to researchers at Michigan State University. Fields of switchgrass, a fast growing perennial often touted as a biomass energy powerhouse, had population levels in between the two extremes.
“Native perennial grasses might provide an opportunity to produce biomass in ways that are compatible with the conservation of biodiversity and important ecosystem services such as pest control,” said Bruce Robertson, one of the researchers involved.
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“This work demonstrates that next-generation biofuel crops have potential to provide a new source of habitat for a threatened group of birds,” Robertson said.
The research was published recently in Global Change Biology Bioenergy.
Currently most ethanol produced in the U.S. comes from corn. Corn requires more inputs of nitrogen fertilizer and generally higher quality soil than wild grasses. Corn also has to be re-planted year-after-year, whereas grass grows back each year.
But producing ethanol from the tough cellulose sugars of grass has been a hurdle for researchers.
As the production of ethanol from cellulose becomes more efficient, the possibility of using native wildlife preserves as renewable sources of energy also becomes more feasible.
Harvesting the biomass, or the usable plant material, may temporarily disturb the ecosystems, but grasslands are used to it. Native grasslands are adapted to seasonal burning and grazing by massive herds of bison, so they may prove resilient to the impacts of periodic harvesting for energy production.
Besides being environmentally responsible, grass could help energy producers save green. Research has shown that both native grasslands and switchgrass monocultures provide a higher return on investment, in terms of energy in compared to energy out.
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Switchgrass, fermented into ethanol, provides 540 percent more energy than was needed to produce it, according to U.S Department of Agriculture (USDA) research published in 2008 in the Proceedings of the National Academy of Sciences.
Switchgrass looks to be more efficient (hence cheaper) than corn as well. On average, switchgrass produced the equivalent of 320 gallons of ethanol per acre. That's over 60 percent more than corn, after considering the fossil fuels used for fertilizers and pesticides, according to the USDA research by Marty Schmer.
Other research has shown the potential of mixed species grasslands grown on poor-quality land. In a 2006 study, published in Science, David Tilman of the University of Minnesota and other researchers looked at the potential for producing biomass energy in crummy soil where no sensible farmer would plant crops.
After a decade of growth and harvest, high species diversity native grasslands showed 238 percent higher bioenergy yields over monocultures of switchgrass.
The energy produced by the grass being burned without fermentation into ethanol was considered. This means the research is most applicable to power plants converting from coal to biomass, for example the University of Missouri at Columbia's power plant.
Producing energy from grasses on low-quality land would also reduce greenhouse gas emissions and agricultural chemical pollution caused by growing corn for ethanol or soy for biodiesel, said the researchers.
Since the grasses Tilman's team studied were grown on land unsuitable for agriculture, they wouldn't compete for land with food crops. And as the Michigan State researchers point out, the land could provide valuable habitat.