Tuesday, April 20, 2010
8-39

Comparative study of the effect of switchgrass feedstock variability on enzymatic digestibility before and after pretreatments studied by CAFI

Nathan S. Mosier1, Youngmi Kim1, Michael R. Ladisch1, Mark T. Holtzapple2, Bruce E. Dale3, Y. Y. Lee4, and Charles E. Wyman5. (1) LORRE/Ag. and Bio. Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (2) Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX 77843-3122, (3) Deparment of Chemical Engineering and Materials Science, DOE Great Lakes Bioenergy Research Center, Michigan State University, 3900 Collins Road, Lansing, MI 48910, (4) Department of Chemical Engineering, Auburn University, 207 Ross Hall, Department of Chemical Engineering, Auburn, AL 36849, (5) Center for Environmental Research and Technology, Bourns College of Engineering, University of California, Riverside, 1084 Columbia Avenue, Riverside, CA 92521

Variability in feedstock quality as a function of cultivar, production location, and harvest time may have significant impacts on enzymatic saccharifaction and biofuels production.  The Biomass Consortium for Applied Fundamentals and Innovation (CAFI) has examined several leading pretreatment technologies applied toward processing switchgrass (Panicum virgatum L.).  Switchgrass varieties can be categorized into two different ecotypes primarily based on latitude of origin: upland and lowland. Upland varieties are more adapted to cold temperature and semi-arid climates and tend to grow shorter and less coarse than low land types. Southern-origin lowland curtivars tend to grow taller and be more bunchy and thicker-stemmed, producing more biomass than upland types.  In this study, we report comparative saccharification yields of three different varieties of switchgrass, two upland types (Dacotah and Shawnee) and one lowland type (Alamo) switchgrass harvested in the fall or in the spring after standing in the field over winter. Comparisons were also made among the types of switchgrass before and after processed by pretreatment technologies as part of the CAFI project (ammonia fiber expansion, aqueous ammonia recycle, dilute sulfuric acid, lime, and neutral pH liquid hot water). These comparisons are of data obtained through identical experimental protocols and data analysis techniques using common supplies of switchgrass.  The key features of different types of switchgrass and the effects these differences had on hydrolysis performance for the applied pretreatment methods are discussed.

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