Impact of Conditioning Prior to Dilute Acid Deconstruction of Biomass for the Production of Fermentable Sugars

Cost of cellulases is a major impediment in commercialization of cellulosic ethanol. To reduce the enzyme doses for the production of fermentable sugars from rice straw (RS), a series of alkali conditioning experiments were conducted prior to dilute acid (DA) pretreatment. This approach resulted in removal of a majority of extractives, ash, acetic acid, and part lignin, and thus resulted in lowering pseudolignin formation thereby increasing enzymatic hydrolysis yields. Glucan hydrolysis of 69.8%, 74.0%, and 83.5% was obtained at 10 wt % water insoluble solid (WIS) using 8 FPU enzyme/g WIS of biomass conditioned using 0.2, 0.4, and 0.5 wt % alkali prior to pretreatment, which is 14–37% higher than the control (61.0%). The overall sugar recovery in these experiments were 69.2%, 70.2%, and 68.5% at 15 wt % WIS resulting in a sugar concentration greater than 120 g/L, which in turn can produce approximately 5–6% w/v ethanol concentration in fermentation broth. It was found that this approach resulted in a decrease of the enzyme consumption vis-a-vis the conventional process by 46.4% to recover the same amount of sugars. This lowering of enzyme consumption has resulted in net savings, after taking into account the cost of alkali used in the conditioning steps

Physical and Chemical Characterization of Various Indian Agriculture Residues for Biofuels Production

Lignocellulosic material (LCM) has been considered as a potent feedstock for biofuel production either as gaseous, liquid, and/or solid fuel to meet the energy demands. Conversion of lignocellulosic materials to biofuels is possible mainly by two processes, i.e., thermochemical and biochemical. For overall efficiency of processes designed to convert the lignocellulosic materials into the desired biofuel, it is important to understand the characteristics of these lignocellulosic components. The present study aims for physicochemical characterization of common lignocellulosic agricultural residues available in India, i.e., rice straw, rice husk, cotton stalk, wheat straw, bagasse, corn stover, sorghum stalk, mustard stalk, corn cob, and jatropha pruning. Physical and chemical characterization of lignocellulosic samples is carried out by higher heating value, crystallinity index, thermal properties, CHNS/O analysis, FTIR, metal analysis, and compositional analysis. Among all of the biomass samples analyzed, corn cob has the highest content of cellulose and hemicellulose, i.e., 61.2% (w/w), making it the most potent feedstock for production of biofuels using biochemical process, whereas cotton stalk has relatively higher thermochemical potential due to its higher heating value (19.2 MJ/kg). Rice husk and rice straw have the highest ash content, i.e., 17.4 and 13.7% (w/w), respectively, indicating a significant amount of undesirable material