Biohydrogen production potential from the organic fraction of municipal solid waste in co- digestion with sewage sludge through high-solids dark fermentation

Background Biohydrogen production from the organic fraction of municipal solid waste (OFMSW) in co-digestion with sewage sludge (SS) through dark fermentation (DF) is emerging as an alternative route for efficient waste treatment and biofuel production. Notwithstanding, there is little experience with a high-solid approach, where practical conditions are created to further develop feasible industrial-scale projects. This study conducted a biochemical hydrogen potential test using a 7L batch reactor at 35°C for 39 days. Parameters such as pH, redox potential, temperature, alkalinity, total solids, and substrate/inoculum ratio were adjusted and monitored. Biogas composition was analyzed by gas chromatography. The microbial characterization of SS and post-reaction percolate liquids was determined through metagenomics analyses. Results Results demonstrate an initial biohydrogen yield of 38.4 Nml/gVS OFMSW, which forms ~ 60% of the produced biogas. Aeration was proven as an efficient inoculum pretreatment method, mainly to decrease the levels of methanogenic archaea and metabolic competition, and at the same time maintain the required total solid (TS) contents for high-solid conditions. The microbial community analysis shows that the biohydrogen production was carried out by specific anaerobic and aerobic bacteria and dominated by the phylum Firmicutes such as the genus Bacillus, Clostridium, Romboutsia; and the phylum Proteobacteria with the genus Proteus. Conclusion These results aid in setting the base ground to further develop the technology and design a larger bioreactor for DF of OFMSW in co-digestion with SS, considering diverse parameters, the manufacturing process, and instrumentation. Thus, this research provides an alternative solution for OFMSW treatment and biohydrogen production and expects to serve as a basis for future research, which may intend to improve biochemical conditions to increase the amount of hydrogen produced, optimize biodegradation and, at the same time, develop an industrial high-solid dark fermentation system that is technically and economically viable.