(639d) Size Reduction Fundamentals for Biomass Conversion

Authors: 
Zhu, J. Y., USDA Forest Service, Forest Products Laboratory


Sieving method has been almost exclusively used for biomass size reduction characterization in the published biomass refining literature. This study demonstrates a methodology for properly characterize specific surface of biomass substrates through two dimensional measurement of each fibers of the substrate using a wet imaging technique. The methodology provides more information than the sieving method for properly characterize biomass substrate for biorefining. The image measured dimensions of individual fibers were used to estimate the substrate external surface based on a cylinder model. The substrate specific surface and mechanical refining energy consumption were then correlated to enzymatic hydrolysis glucose yield. Results indicated that the developed methodology is effective to differentiate various size-reduction and chemical pretreatment processes in terms of cellulose conversion efficiencies and size-reduction energy consumption. Disk milling-I that exposes cellulose is more effective than disk milling-II that exposes lignin in enzymatic hydrolysis. However, DM-I is more energy intensive than DM-II even taking the thermal energy into consideration. Both disking millings that produce fibers are more efficient in enzymatic hydrolysis than hammer milling that produce fiber bundles. Chemical pretreatment is not only increased cellulose conversion, but also reduced mechanical refining energy consumption. The present methodology correctly identified a proprietary pretreatment C as the most efficient pretreatment in terms glucose yield and refining energy consumption.