Researchers from Hanyang University assessed organosolv fractionation for the effective utilization of rice husk
Increasing amount of rice husk is either burned or buried in the ground, owing to lax environmental standards and technological limitations. According to ‘A review on utilization of biomass from rice industry as a source of renewable energy’ published in the journal Renewable and Sustainable Energy Reviews in 2012, global rice production is 685 million tons annually and 137 million tons of rice husk is generated. Several studies are focused on developing efficient uses for rice husk. The composition of rice husk varies according to location. However, in general, rice husk contains 49.5% to 64.2% carbohydrates, including cellulose and hemicellulose, and 13.5% to 40.2% lignin, according to ‘Production and performance of activated carbon from rice husks for removal of natural organic matter from water: A review’ published in the journal ‘Chemical Engineering Research and Design’ in 2018.
Now, a team of researchers from Hanyang University extracted xylose and lignin from rice husk. The team also enhanced the enzymatic digestibility of fractionated solids. Ethanol can dissolve hemicellulose and lignin in the liquid hydrolyzate while leaving a high content of cellulose in the residual solid when it is used as an organic solvent. The team assessed the ethanol organosolv process at several independent variables. To selectively extract the desired component in one stage process, the impact of independent variables were determined and the chemical characteristics of acid-free and acid-catalyzed organosolv precipitated lignin were compared.
The team found that acid-catalyzed organosolv fractionation via a low reaction severity can offer effective results in biorefinery. The team recovered highly pure lignin fractions. Moreover, hydrolyzate can be used for xylose-uptaking fermentations. The cellulose-rich solid fraction, which is an insoluble residue can be hydrolyzed at a low enzyme loading into glucose. According to the researchers, a biorefinery procedure before a five-carbon fermentation process plays a major role as a catalytic conversion of fractionated lignin to offer full valorization of the cellulosic biomass. The research was published in the journal MDPI Energy on May 11, 2019.