Evaluation of biomethane potential of codigested sheep manure and kitchen refuse

A study on the biomethanation potential of codigested sheep manure (SM) and kitchen refuse (KR) was carried out. Both the substrates varied in their C:N ratio, cellulose, hemicellulose and lignin contents, although they had very similar moisture and volatile solid (VS) contents. Anaerobic codigestion to balance the C:N ratio thereby making the process more efficient to help enhance biomethanation is a universally accepted strategy. Various combinations (80:20, 60:40, 40:60, 20:80) were used for biogas production alongside pure SM (100:0) and KR (0:100) to arrive at an efficient ratio using the digested slurry from an active biodigestor as the microbial inoculum. A 40-day experiment was set at 40 °C and pH 7.0 initial conditions, and the effect of the codigestion on the pH, volatile fatty acids (VFA) and the C:N ratio was evaluated. It was observed that the biogas and methane generation were maximal at SM:KR::40:60 combination with 7.0–7.5 pH, 23.3 C:N ratio, and a balanced VFA production and utilisation. The maximum cumulative biogas and methane generated were 2575 mL and 1660 mL, and the calculated biogas and methane generation based on the VS content were 209.35 and 135.13 mL/g VS. Based on the results obtained from the study, it is suggested that sheep manure and kitchen refuse codigestion could help enhance biogas production at 40:60 combination. Although reports on codigestion of other such biogasifiable substrates exist, similar studies could be tried for numerous other nonconventional organic biogasifiable substrates to validate their biomethanation potentials and enhancements.