Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
A multi-scale microscopy approach including multiple light and electron imaging modes was utilized to investigate the impact of different biomass pretreatment reactor configurations on cell wall structure. Corn stover feedstock was pretreated at the same severity (160°C, 5 min, 2.0 wt% H2SO4) in three types of reactors: zipperclave, steam gun and horizontal reactor. Corn stover treated in the horizontal and steam explosion reactor achieved much higher cellulose conversions of 95% and 88%, respectively, after 96 hours; compared to 69% for the zipperclave pretreated sample. The chemical composition analyses of these samples yielded largely similar results except that the horizontal and steam explosion reactors removed slightly more xylan. Imaging at the micro- and nano-scale revealed that the superior performance of the steam gun and horizontal reactors could be explained by the reduced particle size, and increased cellular dislocation, surface texture, delamination, and micro-fibrillation generated within the biomass particles during pretreatment. This study indicates that reactor designs that augment the thermal and chemical energy applied to the pretreatment of biomass with physical energy, can aid in overcoming the recalcitrance of biomass through mechanical disruption of the plant cell wall. The horizontal reactor augments thermochemical pretreatment with explosive decompression of the biomass and the grinding action of the horizontal screw feeder, improving accessibility of the cellulose to cellulase enzymes. The analysis presented here represents significant progress toward the challenge of bringing quantitative physical analysis to what has been a largely qualitative method of biomass characterization.