Effect of Switchgrass Maturity on Ethanol Production via Simultaneous Saccharification and Fermentation
Abstract
Switchgrass has been selected as a substrate to produce ethanol. One method of producing ethanol from switchgrass is through pretreatment followed by saccharification and fermentation. The harvest date of switchgrass could impact the production of ethanol due to changes in plant chemical composition. Kanlow switchgrass was harvested in July, August, September, October, and November in Stillwater, OK in 2008. The switchgrass was comminuted, analyzed for chemical composition, pretreated by hydrothermolysis, and converted to ethanol via simultaneous saccharification and fermentation (SSF). The objectives were to determine changes in structural carbohydrate and lignin contents in switchgrass over a typical harvest season and to determine the effect of switchgrass maturity on the production of ethanol via SSF. Structural carbohydrate and lignin contents increased throughout the harvest period. Extractives content decreased throughout the harvest period. The amount of switchgrass dissolved during hydrothermolysis decreased after September. Ethanol concentration via SSF was highest for the August harvest, followed by July, October, September, and November harvest dates. Initial fermentation rates decreased throughout the harvest period. Ethanol yield in terms of liters per ton of switchgrass was highest for the October harvest, followed by the November, August, July, and September harvests. Much of the increase in structural carbohydrate content over the harvest period was due to a decrease in extractives content, rather than addition of new structural carbohydrates. Increasing lignin content through the harvest period had a negative effect on fermentation rates and yields. The lignin content after pretreatment did not appear to correlate to fermentation rates and yields as did the lignin content of untreated switchgrass. The decreased amount of switchgrass dissolved during hydrothermolysis at the end of the harvest period had a positive effect on ethanol yields. Ethanol yield in terms of liters per ton of switchgrass for July, August, October, and November harvest dates were not significantly different; a significantly lower yield was obtained for the September harvest date.
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- OSU Theses [15752]