Rodolfo Daniel Silva-Martínez

Adequate treatment of the organic fraction of municipal solid waste (OFMSW) in co-digestion with sewage sludge (SS) through dark fermentation (DF) technologies has been widely studied and recognized. However, there is little experience with a high-solids approach, where practical and scalable conditions are established to lay the groundwork for further development of feasible industrial-scale projects. In this study, the biochemical hydrogen potential of OFMSW using a 7 L batch reactor at mesophilic conditions was evaluated. 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 show a biohydrogen yield of 38.4 NmLH₂/gVS OFMSW, which forms ~60% of the produced biogas. Aeration was proven to be 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-solids conditions. The microbial community analysis reveals that biohydrogen production was carried out by specific anaerobic and aerobic bacteria, predominantly dominated by the phylum Firmicutes, including the genus Bacillus (44.63% of the total microbial community), Clostridium, Romboutsia, and the phylum Proteobacteria, with the genus Proteus.

This work focuses on analyzing the physical composition of municipal solid waste (MSW) and the physicochemical characterization of the organic fraction of municipal solid waste (OFMSW) in a city in Northeast Mexico to propose an adequate treatment and valorization system. Diverse samples were analyzed over 5 months at the city of Saltillo landfill, where the daily discarded MSW was classified into household (HW), central market waste (CMW), and public areas and parks waste (PPW). For the HW and CMW, the fraction with the highest proportion was the organic residues from food products, with 22.15 and 25.78%, followed by other organic wastes (manure, yard waste, leaves, etc.) at 12.58 and 10.24%, respectively. Furthermore, the organic fraction was segregated from the rest of the MSW and classified into four subtypes, and their physical composition and physicochemical characteristics were determined. The results contribute to laying the foundations for the proper treatment of the OFMSW not just in the studied region but also in cities with similar conditions. Moreover, the OFMSW’s feasibility in treating via bioenergy technologies is revealed, and this research proposes a biorefinery treatment pathway through dark fermentation followed by high solids anaerobic digestion generating bioenergy and diverse bioproducts.

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.