Enhancing biogas production in anaerobic digestion of MSW with addition of bio-solids and various moisture sources

Abstract

This study aimed to investigate the influence of moisture content on the anaerobic digestion of municipal solid waste (MSW) with the addition of leachate, tap water, wastewater, and sewage sludge. To accomplish this, ten sets of batch experiments were conducted to examine the impact of these various moisture sources on the rate of degradation, indicated by cumulative biogas yield, volatile solids (VS) and total solids (TS) removal. The addition of sludge with leachate and wastewater to MSW resulted in biogas yields that were approximately 30 % higher than the biogas yield from MSW and wastewater alone. Based on the observations of VS removal, it was observed that the addition of sludge degraded about half of the substrate. Therefore, it was observed that the addition of 10 % sludge with leachate and wastewater to MSW provides the best outcomes. The lowest biogas yield was observed with the mixing of tap water with MSW. Further, it was determined that the optimal moisture content for MSW degradation should be greater than 75 % of field capacity (FC). The cumulative biogas yield decreased by more than 50 % when the moisture contents decreased from 100 % to 50 % of FC. The reduction in biogas production at low moisture contents is attributed to limited mass transfer, and the hydrolysis rate also slightly decreases with an increase in total solids. The kinetic study was also carried out using the first order, modified Gompertz, Transference, and Logistic models, and the predicted cumulative biogas yield was compared with the experimental data. The modified Gompertz and Logistic models showed the best fit (R2 ≥ 0.994) with the experimental data for all the sets. The sludge, leachate, and wastewater are produced in large quantities in developing countries, and this study may provide a possible utilization strategy of these wastes for accelerated degradation of MSW.