Following up on a net-energy study published in the January Proceedings of the National Academy of Sciences (PNAS), a team of Agricultural Research Service (ARS) and University of Nebraska-Lincoln (UNL) scientists today reports the on-farm economic costs of producing switchgrass for cellulosic ethanol.
In their PNAS energy-analysis paper, the team reported that switchgrass, when used for cellulosic ethanol, yielded over five times more energy than required to produce the fuel.
In this month's edition of the journal BioEnergy Research, the team describes their study's second part, which examined the farm-scale production costs of switchgrass. Richard Perrin of UNL and Ken Vogel, Marty Schmer and Rob Mitchell--all in the ARS Grain, Forage and Bioenergy Research Unit at Lincoln--conducted the studies.
According to Perrin and Vogel, this study is the most comprehensive one completed to date assessing the economic costs of producing switchgrass biomass on commercial fields.
The team contracted with 10 farmers in Nebraska, North Dakota and South Dakota to commercially grow switchgrass for five years, starting in 2000 and 2001. Throughout the study, the farmers recorded all costs for producing switchgrass biomass, from seed and fertilizer expenses to equipment and labor costs. Total baled biomass yields were recorded for each farm.
On average, switchgrass production costs were $60 per ton. Two farmers with previous experience growing switchgrass were able to limit production costs to $39 a ton. They were among a group of five farmers whose production costs were $50 or less per ton.
That's something farmers elsewhere could probably achieve as they, too, gain production experience with switchgrass, the researchers suggest. Based on the $50-per-ton figure, and assuming a conversion efficiency of 80 to 90 gallons per ton, the farmgate production cost of cellulosic ethanol from switchgrass would be about $0.55 to $0.62 per gallon.
Perrin and the ARS agronomists expect production costs will also decline as new, “ethanol-friendly” cultivars are developed.