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Assessing solid digestate from anaerobic digestion as feedstock for ethanol production

Teater, Charles, Yue, Zhengbo, MacLellan, James, Liu, Yan, Liao, Wei
Bioresource technology 2011 v.102 no.2 pp. 1856-1862
Panicum virgatum, alkalis, anaerobic digesters, anaerobic digestion, biorefining, cellulose, corn stover, energy crops, enzymatic hydrolysis, ethanol, ethanol production, feedstocks, fermentation, glucose, hydrolysates, sodium hydroxide, tanks
Ethanol production using solid digestate (AD fiber) from a completely stirred tank reactor (CSTR) anaerobic digester was assessed comparing to an energy crop of switchgrass, and an agricultural residue of corn stover. A complete random design was fulfilled to optimize the reaction conditions of dilute alkali pretreatment. The most effective dilute alkali pretreatment conditions for raw CSTR AD fiber were 2% sodium hydroxide, 130°C, and 3h. Under these pretreatment conditions, the cellulose concentration of the AD fiber was increased from 34% to 48%. Enzymatic hydrolysis of 10% (dry basis) pretreated AD fiber produced 49.8g/L glucose, while utilizing 62.6% of the raw cellulose in the AD fiber. The ethanol fermentation on the hydrolysate had an 80.3% ethanol yield. The cellulose utilization efficiencies determined that the CSTR AD fiber was a suitable biorefining feedstock compared to switchgrass and corn stover.