AMMONIA RECYCLED PERCOLATION PROCESS FOR PRETREATMENT OF HERBACEOUS BIOMASS

An ammonia-based pretreatment method termed ammonia recycled percolati on (ARP) was developed for pretreating herbaceous biomass like corn co bs/stover mixture (CCSM) and switchgrass. The process involves treatme nt of biomass with aqueous ammonia through a percolation reactor (pack ed-bed, flow-through type). The effects temperature, reaction time, an d ammonia concentration were studied. The extent of delignification in the ARP process was in the range of 60-80% for CSM and 65-85% for swi tchgrass. The ARP process solubilized significant amounts of the hemic ellulose fraction into the pretreatment effluent, yet left most of the glucan fraction intact. The experimental data on CCSM and switchgrass indicate that the ARP is a highly effective pretreatment method. Near -complete conversion of cellulose to glucose was obtained by enzymatic hydrolysis of ARP-treated solid samples of CCSM, whereas conversion w as slightly lower for switchgrass. The rate of enzymatic hydrolysis of ARP-treated samples was substantially higher than that of alpha-cellu lose. The ARP effluents were evaluated for fermentability/toxicity by the xylose-fermenting yeast Pichia stipitis (NRRL Y-11545). The adapta bility of ARP-treated solid samples to simultaneous saccharification a nd fermentation (SSF) was tested for ethanol production using cellulas e enzyme and the yeast, Saccharomyces cerevisiae (NREL, D5A).