By Mike Meyers
Minneapolis Star TribuneGrass could be a better raw resource than corn to make biofuel because it can produce more net energy per acre and absorb more greenhouse gases before being harvested, according to a University of Minnesota study appearing last week in Science [subscription required].
Researchers found that a field planted with a variety of prairie grasses and flowering plants contained more than three times the energy of single-variety grasses. Furthermore, when grown on marginal farmland without the fertilizers and pesticides that corn usually requires, mixed grasses would produce 51 percent more energy per acre than corn grown on fertile land.
There are numerous benefits to using grass rather than corn, the researchers found: Mixed grasses require much less gasoline and diesel fuel to tend and they absorb more carbon dioxide, which offsets the emissions produced in harvesting and processing.
Growing a hectare of grasslands produces about three-tenths of a metric ton of CO2. But within a decade the grasses would absorb 4.4 metric tons of the greenhouse gas, about 14 times as much as is produced. Theoretically, farmers could trade in their emissions reductions for credits on a carbon market, if one is created in the United States.
Additionally, grass is a resource with much fewer demands on it than corn; some worry that widespread production corn-based ethanol will deprive people of food sources. "Unless we produce food and biofuel in an efficient manner, they will be directly competing with each other," said David Tilman, ecology professor at the University of Minnesota. "We will have high prices for both."
Ethanol industry representatives responded tepidly. "Ethanol is ethanol," said Bob Dinneen, president of the Renewable Fuels Association. "We don't have a bias as to what the feedstock is. The marketplace is going to determine what feedstock will prove to be the most economical."
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