Thermal, ultrasonic and electrochemical pretreatment methods to enhance the solubilization of organic substance and methane generation in food waste

Food waste accounts for the largest fraction of municipal solid waste, and one-third of the food produced goes to waste. According to experts, the total food waste generation is expected to increase by 44%, by 2025. In this research, thermal, ultrasonic, and electrochemical pretreatments were used to enhance the solubilization and methane generation using food waste as the substrate. Different pretreatment conditions were examined to determine the optimum conditions for each pretreatment. The highest solubilization was observed at 20 V for 40 min with electrochemical pretreatment. Compared to the control, this was a 40–47% increase. For thermal pretreatment, 80 °C for 90 min, was selected as best conditions. The 2 W/mL for 30 min and 20 V for 40 min pretreatments were selected as the optimum conditions for ultrasonication and electrochemical pretreatments, respectively. The optimum buffer concentration was selected as 300 mg per g VS (volatile solids). The thermal pretreatment had the highest cumulative methane yield of 113.19 mL per g VS, which was an 11% increase compared to the control. This study shows the potential use of pretreatments on food waste to increase the solubilization and enhance methane production.