(755c) Two-Stage Anaerobic Digestion in Co-Digestion of Fruit and Vegetable Wastes with Microwave and Hydrogen Peroxide Pre-Treatment

The production of organic wastes is rapidly increasing in developing nations with a rise in population density. Fruit and vegetable wastes (FVW) are among the major organic wastes that are difficult to dispose of due to its rich organic content. Anaerobic digestion of FVW is an attractive solution, however, it faces operational challenges such as acidification and nitrogen depletion. To enhance the anaerobic biodegradability of FVW, co-digestion with activated sludge (AS) was studied in two-stage anaerobic digestion (thermophilic phase-I and mesophilic phase-II) in the current research. Two mixing ratios of FVW and AS were studied for digester stability and biogas production. The mixing ratio 3:1 (AS:FVW) showed 1.6-fold higher methane yield with enhanced digester stability compared to 1:1. Furthermore, the application of hybrid (microwave and hydrogen peroxide) pre-treatment in feedstock (3:1), enhanced COD solubilization by 33% and subsequently resulted in a 2.17-fold increase in methane yield. Higher protein solubilization was observed compared to carbohydrate in the pretreated feedstock. Besides, the oxidative stress exerted by the pre-treatment was quantified through superoxide radical measurement. The pre-treatment induced prolonged oxidative stress in the initial thermophilic phase, which was downregulated by sludge bioactivity in the subsequent mesophilic phase. Overall, these results suggest that two-stage operation with pre-treatment helps in valorization of FVW by enhancing its anaerobic biodegradability.