Exhaustive characterization on chemical and thermal treatment of sawdust for improved biogas production

This work is aimed to the effective chemical pretreatment of sawdust hydrolysis for enhanced biogas production. Various chemical reagents were used for sawdust hydrolysis. NaOH was found to be the best among all in order to produce highest yield of soluble chemical oxygen demand (sCOD) and phenolic compounds. Therefore, NaOH prospective on delignification and rupture of cell wall of sawdust was determined experimentally using different approaches (NaOH addition, NaOH-microwave, and NaOH-autoclave). The NaOH-autoclave pretreatment showed pronounced effect on cellulose, hemicellulose, and lignin content of sawdust. XRD analysis revealed that 10% increase in crystallinity was observed after NaOH-autoclave treatment. SEM micrographs also depicted that cell wall surface was highly affected by NaOH-autoclave pretreatment. Optimum condition for highest lignin solubilization of 58.6% was found at 10% NaOH concentration and 90-min autoclaving time. Biogas yield was increased by 50.8% at optimum pretreatment condition in comparison to native sawdust. Rate constant and order of bioconversion into biogas was also increased after pretreatment. The maximum methane content in biogas for treated sawdust was found to be 62%.