Methane Production Dynamics of Co-Digestion of Cow Manure and Food Waste Under Mesophilic Condition

A batch experiment of 30 days was carried out under mesophilic (37 +/- 1 degrees C) condition using cattle manure (CM), food waste (FW) and the mixture of cattle manure and food waste with ratios of 3:1(T1), 2:1(T2), 1:1(T3), 1:2 (T4) and 1:3(T5) based on volatile solids to test the biogas production dynamics and potential when the seed sludge was obtained from the effluent of cattle manure and food waste anaerobic co-digestion reactor. An obvious two-stage characteristic with CM, FW and the mixture methane production was simulated by Gompertz model and first order kinetics model was analyzed. The values of the first methane production stage kinetics K-1 of CM, FW, T1, T2, T3, T4 and T5 were 0.0564, 0.1132, 0.0629, 0.0668, 0.0726, 0.087 and 0.0853 d(-1). Then the values of the second methane production stage appeared at day 12, 12, 12, 10, 8 and 8, respectively, along with much higher constants K-2 of 0.1346, 0.1478, 0.1948, 0.2153, 0.2299 and 0.2068. Thus, comparing the values of the two methane production stages, the second stage had a higher methane production rate. According to the kinetics of methane production using Gompertz model, the anaerobic digestion of CM, FW, T1, T2, T3, T4 and T5 got the maximum methane production rate (R-max) of 5.7, 48.1, 10.4, 13.2, 16.2, 22.9 and 28.2 mL CH4 center dot gVS(-1).d(-1) at day 9.6, 4.6, 8.4, 8.4, 7.9, 7.9 and 5.8, then at day 23.8, 11.5, 22.1, 21.2, 20.3, 17.6 and 16.2, 90% of total methane was produced. The batch tests illustrated that adding FW in CM can increase the methane production in comparison with the mono-fermentation of CM, while the best methane production was found in FW mono-fermentation.