Biochemical methane potential and kinetic parameters of goat manure at various inoculum to substrate ratios

Abstract

Anaerobic digestion is a proven technology for managing manure while harvesting natural gas and digestate as a biofertilizer. The biochemical methane potential (BMP), biodegradability, and kinetic parameters of goat manure (GM) were investigated at different inoculum to substrate ratios (ISRs). The cumulative biomethane yields at the ISRs of 0.0, 0.3, 0.5, 0.8, 1.1, 1.3, and 2.6 were 191.7, 214.3, 214.9, 225.9, 222.1, 222.8, and 229.9 mL gvs−1, respectively. The biomethane yield at all ISRs was significantly higher than control (0 ISR). Above the ISR of 0.0, the biomethane yield was similar among all ISRs. The biodegradability of GM at the ISRs of 0.3, 0.5, 0.8, 1.1, 1.3, and 2.6 varied between 73.3% and 78.7% and was statistically similar. In total, 90% of the yield was observed in 31 and 32 days in control and all other ISRs, respectively. The modified Gompertz equation fitted very well (R2 = 0.99) to the BMP of GM but predicted the lag phase (λ) of 3.2–5.2 days against observed 8–10 days among control and other ISRs.