Anaerobic co-digestion of excess brewery yeast in a granular biomass reactor to enhance the production of biomethane

► Brewery yeast was used to produce biogas in an upflow granular anaerobic reactor. ► Mixtures up to 1.1 v/v% yeast are anaerobically degradable without adverse effects. ► In full-scale operation biogas production increased by 38.5%. ► Up to 16% natural gas were replaced in brewery operation. ► Up to 7% in archeal and a 32% dissimilarity in bacterial community were shown.