Feedstock Mixture Effects On Sugar Monomer Recovery From Dilute Acid Pretreatment and Enzymatic Hydrolysis of Lignocellulosic Biomass

For efficient production of biofuels such as cellulosic ethanol, biorefineries will have to be able to accept and process multiple mixed feedstocks such as forest thinnings, agricultural residues, and both woody and herbaceous energy crops. Much is known about effective pretreatment and enzymatic hydrolysis reaction conditions for pure biomass species, but mixture effects are largely unknown. This study looks at the effects of mixtures of various amounts of balsam fir (softwood species) and switchgrass (herbaceous energy crop) on total sugar recovery from aspen (woody energy crop). The pretreatment regime for this study is dilute acid hydrolysis with 0.5% w/v sulfuric acid, 10% w/v solids loading, and 175°C temperature. Time points at one-half, one, and two times the previously determined optimal pretreatment time (Jensen et al. 2010) are being evaluated to investigate the effects of reaction time on total sugar recovery. Enzymatic hydrolysis conditions for this study are; 1% w/v biomass loading, 0.25 ml Accelerase 1500 (Genencore) per gram of initial glucan, 50 mM citrate buffer pH 4.8. Sugar concentrations are determined using high performance liquid chromatography (HPLC). Sugar monomer and oligomer concentrations after pretreatment, and sugar monomer concentrations following enzymatic hydrolysis at 0, 24, 48, and 72 hour time points are determined. These experiments help quantify the importance of lignin (high in balsam) and mineral content (high in switchgrass) on overall conversion efficiency, with an emphasis on performance of enzymatic conversion.