Assessment of biomethanation potential and batch kinetics of the anaerobic digestion of vegetable market waste in serum bottles

The huge quantum of vegetable waste (VW) generated in the country has a tendency to decay rapidly owing to high organic and moisture content, and extremely perishable nature which make it an ideal feedstock for renewable energy production. Initial assessment of biochemical methane potential (BMP) of relatively more acidic cabbage, tomato, capsicum, and bitter gourd wastes resulted in lower biogas accumulation (80–120 mL) and methane yield (0.016–0.028 L/g VS added). On the other hand, higher cumulative biogas production (300–320 mL) and corresponding methane yield (0.280–0.300 L/g VS added) were noted for relatively less acidic radish and fenugreek leaves wastes. The Butyrate/Acetate and Propionate/Acetate levels were above inhibitory concentration in case of former set of VWs with poor methane yield, and were lower than inhibitory concentration in case of latter set of VWs with higher methane yield. Biogas volume and methane yield were observed to be 220 mL and 0.112 L/g VS added respectively during co-digestion of all the seven VWs (MVW) while the same were higher (320 mL and 0.255 L/g VS added) during co-digestion of VWs (HBVW) which had performed better during mono-digestion experiment. The determination coefficients for observed methane production potential of VWs (R2 values) were > 0.9 indicating goodness of fit for all the four kinetic models. However, among the four kinetic models, most accurate prediction of biogas potential was achieved by the logistic function and modified Gompertz models considering the minimum deviations between the measured and predicted biogas yields and lowest values displayed for the statistical indicators RMSE, MAPE, AIC, and BIC. The study highlighted the significance of monitoring substrate composition during the anaerobic digestion for preventing process failure due to over-acidification and also paves the path towards effectively utilizing VW as substrate for biogas production.