Impact of sequential hybrid pretreatment in anaerobic digestion of food waste and garden waste co-digestion on waste characteristics and biogas production

One-third of food produced results as food waste, with no organized and sustainable disposal, and ends up in landfills. Garden waste is yet another significant waste experiencing improper disposal or burning. The present study aims to assess the effect of different pretreatment processes in biogas production from anaerobic digestion of food waste and its co-digestion with garden waste. Feedstock is subjected to thermal and or extrusion pretreatment. A combination of both is the proposed novel sequential hybrid pretreatment method. Feedstock is rich in cellulose I, II, and di/monosaccharides, where pretreatment altered the characteristics and morphology with a steady neutral pH indicating stability. The resultant feedstock exhibited the absence of cellulose II and reduced disaccharides. An average of 0.25 times increase in biogas production is observed with individual thermal and extrusion pretreatment than the conventional digestion. Sequential hybrid pretreated feedstock yielded maximum biogas of 730 and 430 mL/g VSfed in mono digestion and co-digestion over its conventional counterparts. In this study, the modified Gompertz model (R2 of 0.98) is suitable over the first-order kinetics model. Results conclude that sequential hybrid pretreatment leads to significant breakage of complex organic matter in substrates aiding in the efficient digestion process and biogas generation.