Effects of Sequential Sodium Hydroxide Ultrasonication and Hot Water Treatment of Rice Straw and Coconut Shell on Biogas Production

Objectives: This study aims to determine the effects of various pretreatment methods on the biomass properties and biogas yield in the anaerobic co-digestion of agricultural biomass waste co-digested with different biomass feedstocks for power generation applications. Methods: This study was carried out in order to determine the effects of the methane production on the two pre-treatments (3% and 4% w/v NaOH) subjected to sequential NaOH-ultrasonication and Liquid Hot Water treatment for the rice straw and coconut shell feedstocks, which can be used as substrates for the anaerobic co-digestion experiments; using cow manure, digested manures and sewage sludge as inoculant. Findings: Results showed that the methane production increased by 140% and 290% from the pre-treatment of rice straw and coconut shells, respectively. With these, the pre-treated coconut shell subjected to ultrasonication with 3% NaOH and Liquid Hot Water has the best effect among the pre-treatment of biomass feedstocks of rice straw and coconut shell at various NaOH concentrations. Applications: The results of this experiment would give a viable estimate on the possible methane production from co-digestion of these resources. The enhancement of the biogas yield was attributed to the improvement of biodegradability of rice straw and coconut shell through the pre-treatments. The changes of chemical compositions, chemical structures, and physical characteristics made rice straw and coconut shell feedstocks become more available and biodegradable and thus were responsible for the enhancement of the biogas yield. These results are contributing to develop a feasible biogas production from rice straw and coconut shell.