Renewable energy from the solid-state anaerobic digestion of grape marc and cheese whey at high treatment capacity

Abstract

Globally, wine production annually generates some 11 million metric tonnes of grape marc (GM) while the cheese-making industry releases over 200 million m3 y−1 of effluent. Where value-creation mechanisms are absent, such wastes may be channelled to landfills. The study aimed to evaluate the bioenergy potential of the combined treatment of such wastes. Digestion of feedstock at a ratio 3/1 GM/CW (w/w) was conducted in unstirred conditions at 45 °C, following optimisation through the Taguchi Method. Cumulative biogas and methane yields were 0.601 m3 gas kg−1 VS and 0.363 m3 CH4 kg−1 VS, respectively. Firmicutes and Bacteroides mediated hydrolysis and acidogenesis, thus providing metabolites to Methanosarcina. Co-digestion can potentially generate 1330 GW h and 482,000 Mt CO2-equivalents avoidance. Wine and dairy industries jointly present a case for value-creation through a circular economy, thereby reducing the dependency on non-renewables, renewing commitment to the Paris Agreement.