Marginal farmland a potential boon for ethanol crops, CO2 reduction — study

Source: Amanda Peterka, E&E reporter • Posted: Friday, January 18, 2013

Marginal Midwestern farmland — tracts not used for food crops — can produce enough biofuels to reduce the amount of carbon dioxide spewed annually by about 10 million mid-sized cars, according to new research.

While the notion of using marginal lands for biofuel production is several years old, the study published in the current issue of Nature is the first to quantify the biofuel potential and possible emission benefits of marginal lands. The study used 20 years of data from 10 states.

“This research shows that these lands could make a major contribution to transportation energy needs, while providing a substantial climate and — if managed properly — conservation benefits,” said Phil Robertson, a Michigan State University professor of ecosystem science and a co-author of the study, in a statement.

Researchers compared six types of traditional and advanced biofuel systems: conventional and no-till corn-soybean-wheat rotation, alfalfa, poplar, marginal lands that have been abandoned and left to revegetate, and abandoned fields that have been helped along with fertilizer.

They measured several factors — including greenhouse gas emissions, soil-carbon stocks and yields — using data from the National Science Foundation’s Kellogg Biological Station Long-Term Ecological Research site at Michigan State.

The results showed all systems were net sinks of greenhouse gases when the emissions avoided from producing fossil fuel were taken into account.

Grasses and other vegetation in both the unfertilized and fertilized abandoned fields — marginal lands where no food crops were grown — absorbed substantially more CO2 than the other systems.

Using marginal lands for biofuel production, the study says, would not interfere with food-cropping systems or have any indirect land-use effects.

Measuring productivity of different systems and using models to map the Midwest, researchers found, under a conservative estimate, that marginal lands could provide enough biomass to produce 215 gallons of cellulosic ethanol per acre or 5.5 billion gallons of cellulosic ethanol a year. The numbers are based on a scenario in which biomass is collected from an 80-kilometer radius around potential biorefineries.

Those levels equal about 25 percent of the 2022 target for cellulosic biofuel production under the federal renewable fuel standard and, compared to using fossil fuels, reduce carbon dioxide emissions by the equivalent of taking 10 million medium-sized cars off the road, according to an accompanying critique of the study by German researcher Klaus Butterbach-Bahl and Kenyan researcher Ralf Kiese.

“Because it is based on long-term data, this is the first convincing analysis of the impact of biofuel-production systems on global warming,” Butterbach-Bahl and Kiese wrote.

Researchers from the Pacific Northwest National Laboratory and the University of Maryland also participated in the study. The research was funded by NSF, the Great Lakes Bioenergy Research Center and MSU AgBioResearch.