Research by University of Minnesota ecologists and economists David Tilman, Jason Hill, and Clarence Lehman should put the spurs to production of cellulosic biofuels. They published “Carbon-Negative Biofuels from Low-Input, High-Diversity Grassland Biomass” in the journal Science last December.
Studying test plots of perennial grasses, they found that the highest-diversity plots (containing 16 grass species) yielded upwards of 250 percent more bioenergy than a monoculture planting of, for example, switchgrass. That higher energy yield and little need to use fertilizers, pesticides, or run equipment for field work means that diverse grasses provide a net—using existing biofuels production technologies—of 51 percent more usable energy per hectare of marginal crop land than corn and soybeans do per hectare of fertile land.
Added benefits: Food and fuel don’t compete for the same crops or the same land; groundwater filtration, wildlife habitat, and soil fertility are increased; while crop-production costs and the attendant pollution and greenhouse gas emissions are reduced.
The researchers calculate a potential 15 percent reduction in global carbon dioxide emissions. And that’s before they factor in this kicker: Plantings of diverse perennial grasses soak up and sequester CO2 in their roots and soil, making their use in biofuels a net carbon negative across the entire cycle of fuel production and combustion.
