Potential of Agricultural Residues and Hay for Bioethanol Production

Abstract

Production of bioethanol from agricultural residues and hays (wheat, barley, and triticale straws, and barley, triticale, pearl millet, and sweet sorghum hays) through a series of chemical pretreatment, enzymatic hydrolysis, and fermentation processes was investigated in this study. Composition analysis suggested that the agricultural straws and hays studied contained approximately 28.62-38.58% glucan, 11.19-20.78% xylan, and 22.01-27.57% lignin, making them good candidates for bioethanol production. Chemical pretreatment with sulfuric acid or sodium hydroxide at concentrations of 0.5, 1.0, and 2.0% indicated that concentration and treatment agent play a significant role during pretreatment. After 2.0% sulfuric acid pretreatment at 121°C/15 psi for 60 min, 78.10-81.27% of the xylan in untreated feedstocks was solubilized, while 75.09-84.52% of the lignin was reduced after 2.0% sodium hydroxide pretreatment under similar conditions. Enzymatic hydrolysis of chemically pretreated (2.0% NaOH or H 2 SO 4 ) solids with Celluclast 1.5 LNovozym 188 (cellobiase) enzyme combination resulted in equal or higher glucan and xylan conversion than with Spezyme® CP-xylanase combination. The glucan and xylan conversions during hydrolysis with Celluclast 1.5 L-cellobiase at 40 FPU/g glucan were 78.09 to 100.36% and 74.03 to 84.89%, respectively. Increasing the enzyme loading from 40 to 60 FPU/g glucan did not significantly increase sugar yield. The ethanol yield after fermentation of the hydrolyzate from different feedstocks with Saccharomyces cerevisiae ranged from 0.27 to 0.34 g/g glucose or 52.00-65.82% of the theoretical maximum ethanol yield.

Ethanol Production from Sugarcane Bagasse Pretreated by Steam Explosion

“…Lignocellulosic biomass is an attractive raw material for ethanol production because it is an abundant, cheap and renewable resource on earth and includes various agricultural residues that can be converted to liquid transportation fuels [Chen et al, 2007;Dawnson and Boopathy, 2008]. Its structure is chiefly represented by the physical-chemical interaction of cellulose, a linear glucose polymer, with hemicellulose, a highly branched heteropolymer, and lignin, a very high molecular weight and cross-linked aromatic macromolecule [Himmel et al, 2007].…”

Enhanced biogas production from rice straw with various pretreatment : a review

“…The high Ca(OH)2 considerably changed the microstructure of the cell wall and increased the accessibility of contents to anaerobic microorganisms, facilitating the use of soluble compounds with low molecular weights by microorganisms and increasing biodegradability [50]. Lime pretreatment led to limited lignin reduction that ranged from 4.4% to 24.3%, a value considerably lower than those generated by other alkaline chemicals, such as NaOH and NH3⋅H2O [51,52]. Reduced lignin reduction may have resulted from the formation of calcium-lignin complex.…”

Optimization of Alkali Pretreatment from Steam Exploded Barley Husk to Enhance Glucose Fraction Using Response Surface Methodology

“…The steam explosion treatment (explosive autohydrolysis) has been extensively studied as a promising pretreatment process (Duff and Murray, 1996;Vlasenko et al, 1997) The process is generally followed by a fractionation step to separate the main components (Donaldson et al, 1988;Heitz et al, 1991;Beltrame et al, 1992). One of the problems with the steam explosion process is that it does not significantly delignify the lignocellulosic bi- The alkaline pretreatment has received more attention because it is relatively inexpensive, less energy intensive, and effective on many feedstocks such as forage and agricultural residues (Belkacemi et al, 1998;Chang et al, 2001;Chen et al, 2007;Xu et al, 2010). The application of alkaline solutions leads to removal of the lignin barrier, disruption of structural linkages, reduction of cellulose crystallinity, and a decrease in the polymerization degree of carbohydrates (Mosier et al, 2005b;Sun and Cheng, 2002).…”