Effect of inoculums type and optimization of inoculum to substrate ratio on the kinetics of biogas production of fruit and vegetable waste

Abstract

Annually 5.6 million tonnes of FVW are produced in India. Anaerobic digestion (AD) holds the potential of generating renewable energy from this organic waste. Therefore, an attempt has been made to optimize inoculum to substrate (I/S) ratio via biochemical methane potential (BMP) of FVW using two different types of inoculums viz. anaerobic sludge and a mixture of anaerobic sludge and cow dung in (1:1) ratio. Different (I/S) ratios selected for the study were 0.2, 0.3, 0.4, 0.5, and 0.6. Results indicated that anaerobic sludge (AS) along with cow dung (CD) at a (1:1) ratio performed better than AS alone. The highest cumulative biogas yield was obtained at (I/S) ratio 0.3 for AS+CD (1:1) ratio, which is equivalent to 468.82 ml/g VS. On the other hand, the biogas yield using only AS was found to be 459.49ml /g VS. The highest methane content was obtained as 64% and 61.2%, for inoculums AS+CD and AS, respectively. Performance analysis portrayed volatile solids (VS) reductions of 74% and 68% for (AS+CD) and AS, respectively. The kinetic parameters of AD were studied by the modified Gompertz model (MGM) and the first-order kinetic model. The experimental data fitted well with the MGM model.