Lab- and pilot-scale anaerobic digestion of municipal bio-waste and potential of digestate for biogas upgrading sustained by microbial analysis

The challenge of handling the enormous amount of bio-waste that is globally produced on an annual basis can become an opportunity by exploiting such residues for bioenergy production in the form of biogas or biomethane. The application of anaerobic digestion to bio-waste is still limited due to their specific characteristics (e.g., recalcitrant matter, high solids content, etc.) that might lead to process imbalances and microbial toxicity issues. The present study aimed to elucidate microbial ecology in the lab- and pilot-scale biogas reactors fed with bio-waste. The results showed that the indigenous microbial community in the bio-waste was almost extinct during the digestion process. The AD microbiome was mainly composed of members belonging to the orders Clostridiales and Bacteroidales, whose relative abundance dynamically changed to adapt to operational conditions. The increase in organic loading rate led to the proliferation of members associated with the phylum Synergistetes and the transition to versatile acetoclastic/hydrogenotrophic methanogenic pathways. Furthermore, digestate is a suitable biological inoculum and a nutrient supplement to support further biogas upgrading process. The results identified functional microbes that could benefit bio-waste digestion, unveiled insights into microbiome reorganization, and proposed a potential application of the digestate.