Use of Carbon-Based Additives in Bio-Electrochemically Assisted Anaerobic Digestion for Cheese Whey Valorisation

Abstract

This study explores the possibility of utilising electrochemically assisted anaerobic digestion supplemented with carbon-based materials to stimulate methanogenesis. Two different carbonaceous materials—commercial activated carbon (AC), and pyrolysed argan (PA, derived from argan shells)—were employed as supplements, with cheese whey (CW) being used as the substrate. Methane production slightly increased in the electrochemically assisted digesters, potentially translating into a 2–4% increase in the output of industrial digesters. In addition, reactors supplemented with PA also exhibited better production rates (496–508 L·kgVS−1), although there was no observed improvement in the quantity of biogas at the end of the biodegradability experiment. In contrast, when commercial AC was used as the supplement, the start-up phase was accelerated (5 days), although methane productivity decreased (273–352 L·kgVS−1). These observations were supported by microbiological analyses, demonstrating that the reactors with the poorest performance (those supplemented with AC) experienced the most significant decrease in both archaeal and bacterial populations.