Evaluating biogas potential of organic fraction of wholesale market wastes in New Delhi, India: anaerobic co-digestion with sewage sludge and cattle manure

This study investigated the influence of seasonal variation of fruits, vegetables and agrowastes (FVA) generated in wholesale markets in New Delhi, India, for biogas production. The mechanically pretreated FVA wastes were individually co-digested with waste activated sludge (WAS) under mesophilic conditions for 30 d. The combination of radish leaves with WAS exhibited the highest biogas yield of 407.22 mL/g VS fed . Later, four different mixed combinations were formulated based on four different seasons (pre-monsoon, monsoon, post-monsoon and winter) to digest using three different inocula: waste activated sludge (WAS), cow dung and anaerobic sludge. The mixed combination of substrates for the winter season co-digested with WAS provided the highest biogas yield of 699.49 mL/g VS fed . The modified Gompertz model predicted the biogas potential from all the experimental results and simulated that the lignocellulosic substrates exhibited high lag time (> 1). The biodegradability index (BD) was lower (< 50%) for all the individual substrates, other than the case of reactor with radish leaves and WAS. Most of the mixed substrate’s combination exhibited BD above 50% and also showed positive synergistic effects of 1.25 to 1.94, most probably due to the positive attributes of co-digestion strategy. With the future prospects available to improve the digestibility of certain substrates, a thermogravimetric analysis was conducted on them. It suggests that the thermal degradation of each substrate varies according to its individual characteristics. Hence, possibilities of strategizing thermal pretreatment for selected substrates could be further evaluated, delivering improved sustainable energy utilization and enhanced biogas production.