Corn stover is the most profitable cellulosic biofuel feedstock on cropland in the Great Lakes Region at current prices. For perennial biomass crops to earn farmers more than corn, prices or yields would have to change. At biomass prices of $110–$130 per metric ton or yield gains of 50–60%, poplar, switchgrass, and mixed grasses would become attractive. If prices of expensive U.S. miscanthus rhizomes fell to European levels, miscanthus would become attractive. Otherwise, corn remains king.
Agricultural economists Laura James and Scott Swinton teamed with agronomist Kurt Thelen to conduct a comparative breakeven budgeting analysis at Michigan State University and the Great Lakes Bioenergy Research Center. Their profitability analysis of cellulosic energy crops compared with corn appears in the March–April 2010 issue of Agronomy Journal.
The authors calculated the cellulosic biomass prices and yields required for potential energy crops in southern Michigan to earn as much as a corn and corn stover production system. They built the analysis on price and cost of production data from 2006–2009 along with yield values from published literature.
The authors assume that in a world with viable biomass markets, a corn farmer could harvest 38% of stover without damaging soil quality, and they account for extra fertilizer to cover nutrients lost with corn stover removal. If miscanthus rhizome prices in the U.S. were to fall to European levels—a 95% drop—then the high-yielding Asian grass could become profitable at a biomass price of $45 per metric ton.
Otherwise, switchgrass, poplar, and mixed grasses are the next most promising crops, but would require substantially higher prices or yields to become profitable. Without special subsidies, unfertilized prairie and fallow fields did not typically yield enough to compete with corn at any biomass price.
These findings appear as the U.S. government is taking steps to encourage farmers to grow dedicated energy crops other than corn. The Farm Services Agency’s Biomass Conversion Assistance Program offers to share the cost of establishing a cellulosic crop and match biomass sale prices for the first two years. The Energy Security and Independence Act of 2007 mandates that increasing quantities of cellulosic ethanol be blended into the U.S. transportation fuel supply.
“Farmers who grow corn in this part of the country are likely to produce cellulosic biomass in the form of corn stover or cobs,” says economist and study co-author Scott Swinton. “Of course, that could change with environmental policy that rewards the water quality and climate change benefits from perennial crops, but corn looks like the cellulosic bioenergy crop of choice for now.”
Researchers at the Great Lakes Bioenergy Research Center sites in Wisconsin and Michigan are testing
a variety of energy crops to evaluate yields under field conditions. They expect that in two to three years, they’ll be able to update and validate the results of the current study.
Adapted from James, L.K., S.M. Swinton, and K.D. Thelen. 2010. Profitability analysis of cellulosic energy crops compared with corn. Agron. J. 102:675-687. View the full article online at http://agron.scijournals.org/content/vol102/issue2
Switchgrass harvest. Photo by Kurt Thelen.