Study: Switchgrass ethanol can be boosted

WEST LAFAYETTE, Ind., Aug. 31 (UPI) -- Choosing when to harvest switchgrass, coupled with a simple pretreatment, would allow producers to get more ethanol from the feedstock, U.S. researchers say.

"Switchgrass harvested in the spring had more cellulose, but also more lignin," Purdue research scientist Youngmi Kim said. "You do not get the advantage of the increased cellulose content because it's more difficult to extract those sugars because of the lignin."

Lignin, a rigid substance found in plant cell walls, is a significant hurdle to efficient cellulosic ethanol production, Kim said. Besides selecting fall as the harvest time, a pretreatment step -- cooking switchgrass in hot water under pressure for about 10 minutes -- can help work around the lignin, Kim said.

Fall switchgrass given a pretreatment and fermentation with special yeast shows potential to give as much as 800 to 1,000 gallons of ethanol per acre per year, compared with 150 to 250 gallons per year without pretreatment, study leader Michael Ladish said.

Corn ethanol from grain produces about 500 to 600 gallons per acre per year, he said.

"This shows that we can improve the processes and increase the amount of ethanol we get from switchgrass," Ladish said.