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Effect of Field Harvest Method, Timing, and Storage on Enzymatic Hydrolysis of Liquid AFEX Pretreated Switchgrass

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1008845.(doi:10.13031/2013.29738)
Authors:   Venkata Sambasiva Prasad Bitra, Alvin R Womac, William E Hart, Galina V Melnichenko, Timothy Kraus, John Hickman, Dean Acheson
Keywords:   Switchgrass; LAFEX; harvest method; storage; enzymatic hydrolysis

A much greater impact for ethanol in terms of fuel use could be realized if the sugars from more recalcitrant cellulosic biomass could be converted to ethanol. Pretreatment is an important operation to reduce recalcitrance of biomass for bioconversion process. Herbaceous switchgrass could be a potential energy crop for future bioethanol demand. Switchgrass was field scale harvested in 1st cut of two cut, single cut (early), 2nd cut of two cut (early), single cut (late), and 2nd cut of two cut (late) harvest stages. Bales of 1st cut of two cut switchgrass were stored without protection in the field, whereas single cut (late) switchgrass was stored as bales under tarpaulin and as chop without protection in field plus under tarpaulin. Single cut (early) samples were also ensiled as a preservation technique. Samples were pretreated using liquid ammonia fiber explosion process (LAFEX) at 100C in which the ammonia was maintained in liquid form throughout. LAFEX samples were enzymatic hydrolyzed for 72 h using Accellerase 1000 enzyme. Single cut (late) crop resulted in increased total sugars (68.5%) upon wet chemical analysis. But, ensiling process reduced the sugars by 2%. Enzymatic digestibility of single cut (late) switchgrass was highest (55.7% based on fresh matter) and ensiled single cut (early) switchgrass was 50.3%. Inner portion of 1st cut of two cut bale stored for 13 months gave 63.7% digestibility. The most dramatic reduction in cellulosic ethanol potential was from portions of the bale that were wet continuously due to contact with the ground.

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