Seasonal variation in biogas production in reinforced concrete dome biogas plants with buffalo dung in Pakistan

In this study, a reinforced concrete dome biogas plant processing buffalo dung was functioned to investigate the seasonal variations in biogas production, biogas composition, and loss of volatile solid and methane potential of digestate slurry. These analyses were undertaken from January to May 2019. The biogas quality was assessed using gas chromatography and biogas production was measured through the G4 VuGas diaphragm gas meter while methane potential was examined on biochemical methane potential (BMP) assays under mesophilic conditions. In January, when the average digester temperature was 26.1 °C, the minimum biogas production was 0.23 ± 0.004m3/kg VSadded with 67% CH4 and 32.9% CO2. In May, the average digester temperature rose to 36.1 °C and the maximum biogas yield obtained increased to 0.384 ± 0.006m3/kg VSadded, comprising 71% CH4 and 28.8% CO2. In the cold season during January, the percentage losses of biogas production were recorded to be 41% because of lower slurry temperature and accumulation of fatty acids. The average slurry temperatures within the digester during the cold season were 21.3 ∘C at 6 A.M. and 21.9 ∘C at 3 P.M., increasing to 36 ∘C at 6 A.M. and 36.2 ∘C at 3 P.M. for the warm season. In addition, the methane potential of 115NmL/g VSloss was observed from the digestate slurry through BMP test. The concrete dome biogas plant is favorable for its low cost and was shown to produce adequate amount of biogas to fulfill the domestic requirements during both warm and cold months in Pakistan.