Charles E. Wyman*, Michael Brennan, Alvin Converse, Matthew Gray, Sigrid Jacobsen, Xia Li, Chaogang Liu, Todd Lloyd, Suzanne Stuhler, Bin Yang

Thayer School of Engineering

Dartmouth College

8000 Cummings Hall

Hanover, NH 03755

Phone: (603) 646-3193

Fax: (603)646-2277

E-mail: Charles.wyman@dartmouth.edu

Dilute acid hemicellulose hydrolysis is often favored for biomass pretreatment, and our current research focuses on improving the understanding of this technology to accelerate applications and cost reductions. Hemicellulose removal changes with solids concentration and flow through the solids, and novel mass transfer models can better explain these observations than conventional first order kinetics. Oligomers appear to play a more important role in hemicellulose hydrolysis than previously considered, with high degree of polymerization (DP) soluble oligomers rapidly forming and shifting to lower DP species over time, and depolymerization models can improve our insight into these DP changes. New measurements show xylo-oligomer solubility to be great enough that long DP species could enter solution quite readily, and adding mineral acid appears to enhance yields through accelerating oligomer reactions toward monomers and reducing the importance of direct oligomer degradation. Cellulose digestibility can be related to both lignin and hemicellulose removal for flowthrough systems, and observations of lignin dissolution with water flow through the solids suggest that lignin alterations during hemicellulose hydrolysis could improve digestion for both batch and flow operations. In addition, additives have been identified that reduce enzyme loadings for a given yield or enhance yields at a given enzyme loading for pretreated biomass.