Co-digestion of lawn grass with cow dung and pig manure under anaerobic condition

The main objective of this study was to determine optimum biogas production by examining the effect of co-digestion of lawn grass with cow dung and pig manure. In order to conduct this experimental research, each of the substrates was co-digested with lawn grass at varying mixing ratios at stable, thermophilic (45 °C) temperatures, over a retention time of 16 days. Results indicated that co-digesting lawn grass with cow dung and/or pig manure may enhance biogas production and methane content. The results also imply that pig manure may be a more appropriate co-substrate to mix with lawn grass as it indicated a longer biogas potential for a relatively extended period of time, particularly when the lawn grass to pig manure mixing ratio was an even 30:30 g. Cow dung and lawn grass at a mixture 20:40 g had the highest biogas production, bio-methane potential. The C:N ratio, however, seems to be the main contributing factor in biogas yield hence the differences in yield for the different mixtures and substrates. Methane content of biogas was at its lowest levels for mono-digestion of lawn grass. However, mono-digesting lawn grass has a higher bio-methane potential and biogas accumulation over time when compared to a mixing ratio of pig manure:lawn grass of 40:20 g. The best possible bio-methane and biogas production were achieved when lawn grass was co-digested with both pig manure and cow manure at the ratio of, a 15:15:30 g which is attributed to the balanced nutrients and buffering in the digester.