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Poster Presentation 1-11
Dilute Sulfuric Acid Pretreatment of Corn Stover in a Pilot-Scale Reactor: Investigation of Yields, Kinetics, and Solids Enzymatic Digestibilities
Daniel J. Schell, Jody Farmer, Millie Newman, and James D. McMillan
National Bioenergy Center National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, CO 80401-3393
Corn stover is a domestic feedstock that has potential to produce significant quantities of fuel ethanol. Comprehensive yield and carbon balance information and validated kinetic models for dilute sulfuric acid pretreatment of corn stover, have not been available, however, and this has hindered the estimation of process economics and also limited the ability to perform technoeconomic modeling to guide research. To better characterize pretreatment and assess its kinetics, we pretreated corn stover in a continuous 1-ton/d reactor. Corn stover was pretreated over a range of conditions, using residence times of 3-12 minutes, temperatures of 165°-195°C, and sulfuric acid concentrations of 0.5%-1.4% (w/w). Rigorous xylan conversion yield and carbon balance data were collected at each run condition. Performance results were also used to estimate kinetic model parameters assuming biphasic hemicellulose hydrolysis and a hydrolysis mechanism incorporating formation of intermediate xylo-oligomers. In addition, some of the pretreated solids were tested in a simultaneous saccharification and fermentation (SSF) process to measure the reactivity of their cellulose component to enzymatic digestion by cellulase enzymes. Monomeric xylose yields of 70%-74% and total xylose yields (monomers and oligomers) of 70%-79% were achieved, depending upon the severity of the pretreatment. Cellulose conversion yields in SSF of 80-87% were obtained for some of the most digestible pretreated solids.
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