Rebecca Garlock1, Venkatesh Balan2, Bruce E. Dale2, Venkata Ramesh Pallapolu3, Y.Y. Lee3, Youngmi Kim4, Nathan S. Mosier4, Michael R. Ladisch4, Mark T. Holtzapple5, Matthew Falls5, Rocio Sierra5, Jian Shi6, Mirvat A. Ebrik6, Tim Redmond6, Bin Yang6, Charles E. Wyman6, Bryon S. Donohoe7, Todd B. Vinzant8, Richard T. Elander9, Bonnie Hames10, Steve Thomas10, and Ryan E. Warner11. (1) Chemical Engineering and Materials Science, Michigan State University, 3900 Collins Rd, Lansing, MI 48910, (2) Deparment of Chemical Engineering and Materials Science, DOE Great Lakes Bioenergy Research Center, Michigan State University, 3900 Collins Road, Lansing, MI 48910, (3) Chemical Engineering, Auburn University, 212 Ross Hall, Auburn, AL 36849, (4) LORRE/Ag. and Bio. Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (5) Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX 77843-3122, (6) Center for Environmental Research and Technology Department of Chemical and Environmental Engineering Bourns College of Engineer, University of California at Riverside, 1084 Columbia Avenue, Riverside, CA 92507, (7) Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, (8) Chemical and Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, (9) National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, (10) Ceres, Inc., 1535 Rancho Conejo Blvd, Thousand Oaks, CA 91320, (11) Genencor, A Danisco Division, 925 Page Mill Road, Palo Alto, CA 94304
During the ethanol production process, a pretreatment step is necessary prior to enzymatic hydrolysis for effective conversion of lignocellulosic biomass to soluble sugars. For the biorefinery, the choice of pretreatment method is not trivial, as there are a number of different thermochemical pretreatments and each has unique characteristics. Because of this, it is extremely important to have a common basis and set of analytical methods when evaluating the differences between pretreatment methods.
For this project, six different chemical pretreatments were compared as part of the Consortium for Applied Fundamentals and Innovation (CAFI): ammonia fiber expansion [AFEX] (Michigan State University), dilute sulfuric acid (University of California-Riverside), lime (Texas A & M University), liquid hot water (Purdue), soaking in aqueous ammonia [SAA] (Auburn), and sulfur dioxide impregnated steam explosion [SO2] (University of California-Riverside).
For each of these pretreatments, material balances were analyzed around the optimal pretreatment and subsequent enzymatic hydrolysis of a common feedstock, Dacotah switchgrass. All material balances were based on 100kg of dry biomass entering pretreatment. Washing following pretreatment was considered optional and if performed, was also included in the material balance. Composition analysis was to be performed on all solid/slurry streams and monomeric and oligomeric sugar content was to be determined for all liquid streams. Water use during the entire process was also to be reported, with particular attention given to the pretreatment and washing steps. Enzymatic hydrolysis experiments were performed under the same experimental conditions and enzyme loadings. For each pretreatment, the mass closure for the key species and the glucose, xylose and lignin solubilization for each stage were reported and these results were compared between pretreatments.
