On-farm Pretreatment Technologies for Improving Enzymatic Degradability of Cellulose and Hemicellulose Present in Perennial Grass

This research investigated the ability of on-farm pretreatments with acid, alkali, ozone or novel enzymes to improve enzymatic degradability of cellulose and hemicelluloses in biomass at the biorefinery. Two perennial grasses, switchgrass (Panicum virgatum) and reed canarygrass (Phalaris arundinacea L.), were direct-cut harvested, pretreated, and stored anaerobically for 30 d. Pretreated and untreated samples were fermented to ethanol by Saccharomyces cerevisiae in the presence of commercial cellulase for 72 hr to ethanol. Xylose yields were also measured following fermentation because it is not metabolized by S. cerevisiae. Sulfuric acid and lime pretreatment technologies look promising considering the high conversion yields and ease of application. Efficiencies of nearly 80% for cellulose conversion to ethanol and hemicellulose to xylose were realized, albeit at high chemical loadings. Ozonolysis results demonstrated similar success, but integration of this technology into current storage systems will be challenging. Enzyme addition (xylanases or feruloyl esterase) at ensiling only marginally improved conversion efficiency.