Exploring Dark Fermentation Effluent in Two-Stage Anaerobic Digestion

Dark fermentation and anaerobic digestion are anaerobic fermentation processes that use organic matter as feedstocks under anaerobic microbial conditions. Buswell’s equation can represent anaerobic fermentation in accordance with the elemental composition of any organic matter. Compared to 1-stage anaerobic digestion, 2-stage anaerobic digestion can better enhance biohydrogen and biomethane production. In a 2-stage anaerobic digestion, dark fermentation effluent is considered an intermediate between the first dark fermentation stage and the second anaerobic digestion stage. However, currently, there is no established study on the general elemental composition of a dark fermentation effluent. The purpose of this research is to use Buswell’s equation to explore this process. This research developed an empirical Buswell’s equation for biohydrogen as a model through the integration of theoretical Buswell’s concept and experimental biohydrogen potential. This model identifies the elemental composition and characteristics of a dark fermentation effluent and improves the understanding of the correlation between an organic matter and its dark fermentation effluent. When the theoretical biomethane potential of dark fermentation effluent is found, the valid biodegradability index of 2-stage anaerobic digestion can be elucidated.