Synergistic effect of combined pretreatment in solubilizing fruits and vegetable residue for biogas production: Hydrolysis, energy assessment

The present study focusses on liquefying potential of fruits and vegetable residue through Dimethyl sulphoxide (DSMO) combined ultrasonic pretreatment (DCUP). Ultrasonic power input variation, solid concentration, soluble organic release (SOR) and specific energy (SE) input were used as parameters to assess the pretreatment efficiency. At optimised condition (ultrasonic power 90 W; solid concentration 30 g/L and surfactant dosage 0.008 g/g SS), greater percentage of SOR rate of 22% was achieved in DCUP than ultrasonic pretreatment (UP) (17%) with specific energy consumption of 5400 kJ/kg TS. Biofermentation assay in terms of volatile fatty acids (VFA) indicates higher VFA production in DCUP (1800 mg/L) than UP (1200 mg/L). Biochemical methane potential assay showed significant methane yield of about 190 mL/g COD through non-linear regression model, and the achieved energy ratio was found to be 0.8 for DCUP. Thus, Dimethyl sulphoxide combined ultrasonic pretreatment considered as the energetically efficient process.