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Using hot water pretreated corn stover liquor in dry grind ethanol process to improve ethanol yields
S. KIM (1), D. Lee (1), M. Bohn (1), Y. Jin (1), K. Rausch (1), M. Tumbleson (1), V. Singh (1) (1) University of Illinois at Urbana-Champaign, , U.S.A..

Cellulosic ethanol plants have started operating at commercial scale; however, challenges related to high cost of pretreatment still exist. As an alternative to new cellulosic ethanol plants, mildly pretreated corn stover liquor can simply be incorporated into the existing dry grind process. Mild pretreatment, such as hot water pretreatment, does not require chemicals and special pretreatment reactors used for acid or alkali pretreatment processes, lowering capital costs for modification of the existing dry grind process. Hot water pretreatment produces a minimal amount of inhibitors (furfural, acetic acid, hydroxymethylfurfural and formic acid), which would not decrease enzyme activities or yeast viability of the existing dry grind process. C5 and C6 sugars hydrolyzed and released into the liquor during pretreatment could be fermented into ethanol by engineered yeasts and increase ethanol production per unit land. Corn stover has 22 to 28% hemicellulose and 39 to 42 % cellulose. When corn stover was hot water pretreated at 180°C for 20 min with 20% solids, 50% of hemicellulose and 10% of cellulose were solubilized. To perform the dry grind process with 30% solids, 70% of harvested corn stover would need to be pretreated. Theoretically, this could result in an additional 0.4 to 0.5 gallons of ethanol from one bushel of corn.