Evaluation of co-digestion and pretreatment on lignocellulosic substrate biodegradability and methane production in non-continuous mesophilic reactors

This research aimed to investigate co-digestion and the effects of alkaline pretreatment conditions on substrate degradability and methane production from municipal solid waste (MSW) and sewage sludge (SS) in a pilot and experimental approach in non-continuous reactors with a retention time of 30 days. For this purpose, co-digestion of the organic fraction of MSW and SS with 5 mixing ratios of raw materials was evaluated to evaluate the biogas and methane production from it in with mesophilic temperature conditions (37 °C). Therefore, the results showed that the increase of SS (up to 40% by weight of raw materials) in feed led to increased methane yield, while longer retention times were obtained by increasing the percentage of MSW. So, the ratio of MSW (60%) and SS (40%) (60:40) was determined as the preferred ratio for optimal biogas production. Based on the preferred ratio, the effect of different concentrations of alkaline pretreatment (2, 6 and 10% NaOH) for different time periods (1.5, 3 and 6 hours) on the biodegradability of MSW, biogas and methane production was evaluated. The results showed that the best improvement was with the treatment at a concentration of 6%NaOH for 3 hours, which led to a 30% improvement in methane production. Other treatments were also effective, in which 6%NaOH treatment for 1.5 hours resulted in a 17% improvement in methane yield compared to the control sample. Therefore, alkaline pretreatment significantly improves the decomposition of solid organic waste and thus increases methane production.