Influence of chemical pretreatment, inoculum source, and temperature on the recovery of methane-rich biogas derived from anaerobic digestion of recycled potato peel waste: Experimental and kinetic studies

Anaerobic digestion (AD) is a method commonly applied for the management of organic wastes to generate sources for sustainable energy. In this study, the influence of the inoculum source on the recovery potential of methane-rich biogas from potato peel waste (PPW) at both mesophilic and thermophilic conditions was examined in 12 digesters operated in a batch mode. Effect of chemical pretreatment of the PPW was also considered. Three sources of inoculum including cattle dung (CaD), chicken dung (ChD), and sheep manure (ShM) were examined. The results revealed that the highest CH4 yields from pretreated PPW at thermophilic conditions were 142.91, 172.98, and 146.85 mL CH4/gVS from ShM, ChD, and CaD, respectively. Also, the results demonstrated that the methane-rich biogas recovery from PPW with chicken dung was higher than its production when using sheep manure and cattle dung inoculums by approximately 22% and 5%, respectively, at mesophilic conditions. The increase of methane recovery from alkaline-pretreated PPW was higher by 33% than its yield from the raw untreated PPW at mesophilic conditions. At thermophilic conditions, methane yield enhanced by 88%, 85%, and 74% using inoculums cattle dung, sheep manure, and chicken dung, respectively. Also, the influence of C/N on the anaerobic digestion process was taken into consideration in this study. Kinetics of the AD process was assessed by the modified Gompertz model. Significant conformity was obtained between experimental results and those assessed by modified Gompertz model for methane yield with coefficients of correlation (R2) > 0.98 indicating favorable conditions of the AD process.