Bio-hydrogen and bio-methane potentials of brewery wastewater with brewer's spent grain in batch sequential thermophilic-mesophilic two-stage anaerobic co-digestion

In recent years, proper waste management has become necessary to minimise environmental degradation and facilitate the transition to a more sustainable, circular economy. Among these, organic waste from the agro-food industry is growing continuously. In Europe, the brewing industry plays a major role in production and consumption, contributing significantly to the increasing amount of waste, in particular wastewater and spent grains. Anaerobic digestion is a technique that meets the objectives of the circular economy and involves the reduction and valorisation of organic waste and the production of bioenergy. The aim of the research was to assess the potential for generating hydrogen (BHP - Biochemical Hydrogen Potential) and methane (BMP - Biochemical Methane Potential) in the sequential process of acidogenic-methanogenic anaerobic digestion of beer wastewater and anaerobic co-digestion of beer wastewater and spent grains, evaluating the influence of the addition of spent beer grains at different process steps. The results showed that the addition of spent grains to the wastewater in the acidogenic step led to the best results in terms of hydrogen (25 mL H2/g VS and 127 mL H2) and methane (42 mL CH4/g VS and 206 mL CH4). Spent grains added to the wastewater at the beginning of the methanogenic phase achieved lower results. This work gives useful information to perform anaerobic co-digestion achieving the highest biogas yield and degradation of organic matter with brewing industry waste.