Towards improving biomethane production in anaerobic co-digestion processes under electrochemical pretreatment

Abstract

The need to strengthen the principles of the circular economy promotes the development of efficient technologies for the valorization of agro-industrial residues. Residues such as rapeseed straw and cheese whey pose limitations to their biological conversion into biomethane through anaerobic digestion. Different strategies, such as co-digestion and substrate pretreatment, have emerged as suitable tools to ensure process feasibility. Co-electrohydrolysis has emerged as a novel strategy for the pretreatment strategy of organic residues to promote solubilization and improve the biodegradability of inherently recalcitrant residues. However, the application of co-electrohydrolysis as a pretreatment for the anaerobic co-digestion of cheese whey and rapeseed straw remains barely explored. The specific energy input required to achieve the maximum improvement in methane yield during the anaerobic digestion of cheese whey was determined. The effect of electrohydrolysis on methane production depended on the co-substrate composition. The maximum increase under soil–cheese whey conditions was 9.05 %, whereas progressively higher improvements were observed as the proportion of rapeseed straw increased, reaching up to 78 % under free cheese whey conditions. Although balanced co-substrate ratios resulted in improved methane yields with energetically feasible processes, no synergistic effects were observed at any of the mixing ratios of cheese whey and rapeseed straw.