Enhancement of Biogas Production from Anaerobic Co-Digestion of Rice Straw and Thickened Waste Activated Sludge with Hydrodynamic Cavitation Pretreatment

Nowadays, the transition to a sustainable future is a critical step to reduce dependence on fossil fuel energy sources, which are non-renewable and increases greenhouse gas emissions. Anaerobic digestion is a viable bioenergy technology that can help with this transition by producing biogas from many types of biomass wastes. The aim of this study was the improvement of biogas yield from co-digestion of rice straw (RS) and thickened waste activated sludge (TWAS) by the application of hydrodynamic cavitation (HC) pretreatment. The results revealed that the highest biomethane production was obtained from RS and TWAS co-digestion with both pretreated with HC pretreatment (300 L/kg-vs) compared with 190 L/Kg-vs for co-digestion without pretreatment. Furthermore, the amount of energy production from the co-digestion of TWAS and RS with pretreatment was evaluated to be 9156 MJ/t, 62.4% increase in comparison with the co-digestion without pretreatment. According to the results of the economic analysis, co-digestion of RS and TWAS with pretreatment could achieve a net profit of 61.85 U$/t. The modified Gompertz model was also used to investigate the effect of pretreatment on biomethane production kinetics. The findings of this work suggest that the co-digestion of RS and TWAS with HC pretreatment can increase biogas production, energy transformation efficiency, and economic benefit.