Study explores replacing corn with energy grasses

By Kris Bevill | July 15, 2011

A study funded by BP’s Energy Biosciences Institute has concluded that growing dedicated energy grasses on land currently used to produce corn could reduce greenhouse gas emissions (GHGs) and transition the U.S. Midwest from being a net source of GHG emissions to a net sink. Using a computer model to simulate miscanthus and switchgrass growth in the central U.S., researchers found that replacing 30 percent of the least productive corn acres with the energy grasses could result in increased biofuel feedstock production, improved corn yields and fewer GHG emissions.

“Both switchgrass and miscanthus are perennial grasses, which means that you don’t have to till every year, you don’t have to plant every year, so there’s much less soil disturbance happening than with corn,” said Sarah Davis, Energy Biosciences Institute feedstock analyst and one of the leaders of the study. “And because the root system remains in place year after year, there’s more carbon going into the soil.”

Of the two energy grasses, miscanthus was found to be the most productive and environmentally beneficial. It can be grown on marginal lands without the use of fertilizers, unlike switchgrass, and is higher yielding than switchgrass, said Even DeLucia, a professor of plant biology at the University of Illinois and the EBI researcher who co-led the study with Davis. He said the study did not take into consideration the difficulties surrounding harvest of miscanthus or switchgrass from marginal acres. The study also assumed that machinery for harvest would be readily available and that there would be a reasonably high efficiency of conversion to ethanol once the crops were harvested. “We know that these grasses are enormously productive; we know the agronomy works; we know the ecology works,” he said. “So the next step is to break down the economic barriers by making an efficient conversion chain from lignocellulosics to ethanol. As far as I know, we’re not actually producing ethanol from any of these grasses, so I wouldn’t be building my biorefinery today based on just these feedstocks.”

BP is currently developing a 36 MMgy plant in Highlands County, Fla., through its subsidiary, Vercipia Biofuels, which will produce cellulosic ethanol from energy grasses. The project includes a 20,000-acre energy grass seed farm, which BP began working on late last year. The company said recently it expects to break ground on the production facility next year. The facility is scheduled to come online in 2013.