Effect of Solid Loadings and Urea addition on Biogas production from the Co-Digestion of Rice Straw with Cow Dung

This paper investigated the anaerobic co-digestion of RS and CD at lower solid loadings of 5, 10% and 15% TS. It also studied the effect of urea addition on biogas yields after 20 days retention time. These experiments were also carried out at different substrate mixing ratios of RS-CD 1:1 and RS-CD 1:2. The anaerobic digestion was carried out in a digester designed and fabricated locally with retention time of between 40-60 days with results showing a maximum biogas yield of 116 L/kg TS and 104 L/kg TS for 10% TS at RS-CD 1:2 and RS-CD 1:1 respectively. Experiments carried out at 15% TS showed the lowest biogas yield of 72.1 L/kg and 81.2 L/kg for RS-CD 1:1 and RS-CD 1:2 respectively. Results also showed that studies carried out at RS-CD 1:1 showed higher biogas yields for substrate concentrations of 5%, 10 % and 15% TS when compared to corresponding experiments carried out at a mixing ratio of RS-CD 1:2. This study also showed that supplementing the anaerobic digestion with 0.5% urea increased biogas yield by 15-19%.