Sustainable Bioprocess Combining Fed-Batch Pretreatment Followed by Semi-Continuous Anaerobic Digestion of Brewer's Spent Grains for Biomethane Production

The development of novel and sustainable bioprocesses for the valorization of agri-food by-products is required for the food industry to transition to a circular economy. The objective of this study to evaluate a sequential process consisting of fed-batch pretreatment followed by semi-continuous anaerobic digestion of brewer's spent grains for the production of biomethane and bioenergy. Anaerobic digestion was conducted under mesophilic and methanogenic conditions, and the digestate and corresponding biogas were characterized to determine the process efficiency. Experimental results indicate that the fed-batch pretreatment improves the biogas production obtained from the semi-continuous process. The methane yield during the fed-batch pretreatment was 11.89 L CH4/kg TVSadded, while in the semi-continuous process, the yield was 30.61 L CH4/kg TVSadded. The biogas produced in the semi-continuous process could generate electricity (66.9 kWh/t) and heat (316.75 MJ/t), avoiding greenhouse gas emissions (20.81 kg CO2eq/t). Implementing the novel anaerobic digestion system could be a promising approach for the valorization of brewery by-products, producing renewable energy from biomass.