Anaerobic co-digestion of sludge, sugarcane leaves, and Corchorus stalks in Egypt

This paper mainly introduces the potential of methane yield from co-digestion of primary sludge (PS) and the proposed new waste materials of sugarcane leaves (SL) and Corchorus stalks (CS) in Egypt. This paper includes three parts. In the first part, anaerobic co-digestion of PS, SL, and CS at different carbon-to-nitrogen (C/N) ratios was studied to determine the best C/N ratio. The results indicated that the maximum cumulative methane yields (CMYs) were observed at a C/N ratio of 18, which was associated with the highest volatile solid (VS) removal rate (74.41%). In the second part, the effect of using two types of inoculum (fresh cow manure (CM) and rumen content from slaughterhouses (RS)) on increasing the production of methane was investigated. Clearly, using CM as inoculum showed a superiority of the production of methane from co-digestion of PS, SL, and CS. The maximum CMYs were observed using the CM as inoculum from co-digestion of PS, SL, and CS. It was higher about 1.26 times more CMY using RS as inoculum. In the third part, the possibility of enhancing biogas yields from semi-continuous co-digestion of PS, SL, and CS using different organic loading rates (OLR) of 0.5, 1.0, and 2.0 was conducted. The highest biogas production rate was observed at an OLR of 1.0 gVS/(Lreactor.d) that coincided with the optimum VS removal rate. Statistical analysis of the results was conducted using analysis of variance (ANOVA) test, and the C/N ratio of 18 is statistically the best enhanced ratio. Overall, the feasibility of maximizing the methane productivity considering the anaerobic co-digestion of PS, SL, and CS under the optimal operating conditions and configuration was proved.