Thermophilic and mesophilic anaerobic digestion of soybean molasses: A performance vs. stability trade-off

Author(s)

Paulinetti, Ana Paula ; Guerieri, Fernanda Furtunato ; Augusto, Isabela Mehi Gaspari ; Lazaro, Carolina Zampol ; Albanez, Roberta ; Lovato, Giovanna ; Ratusznei, Suzana Maria ; Rodriguesa, Jose Alberto Domingues

• Document type: Journal article
• Source: Journal of Environmental Management; v. 370, p. 14-pg., 2024-10-03.

Abstract

One of the factors that has a direct impact on anaerobic digestion is the applied organic loading rate (OLRA). Increasing OLRA can boost methane production but can also cause process failure. As a result, establishing the appropriate OLRA for the procedure is critical. This study evaluated the effect of increasing the OLRA using soybean molasses in a thermophilic anaerobic reactor (R-Thermo), as well as the effect of feeding strategy and co-processing with okara. Furthermore, the performance versus stability trade-off between R-Thermo and mesophilic anaerobic digestion (R-Meso) was investigated. The increase of OLRA from 10 to 15 and 20 kg-COD/m(3)/d led to a decrease in COD removal efficiency (90, 86, and 75%), methane yield (12.0, 11.6, and 9.9 mol-CH4/kg-COD) and an increase in total volatile acids concentration (251, 456, and 1393 mg-HAc/L, respectively). At 15 kg-COD/m(3)/d, R-Meso performed similarly to R-Thermo, and at 20 kg-COD/m(3)/d, R-Meso outperformed (81% COD removal efficiency, 9.3 mol-CH4/kg-CODrem and 154.5 mol-CH4/m(3)/d). Temperature greatly influenced the distribution of metabolic pathways, as shown by thermodynamic and kinetic analyses, thus impacting bacterial diversity. At 55 degrees C, amongst the bacterial genera, Tepidiphilus stood out (>28.2%), followed by Acetomicrobium, Coprothermobacter and Candidatus_Caldatribacterium. The OLRA clearly impacted the archaeal community; Methanothermobacter (77.4%) was favored over Methanosarcina (14.8%). Under thermophilic temperature, it seems that syntrophic acetate oxidation (SAO) bacteria might have competed for substrate with acetoclastic methanogens, while in R-Meso microorganisms responsible for the initial steps of organic matter breakdown, such as members of the Firmicutes and Proteobacteria phyla (at least 67%), were dominant. In summary, R-Meso, characterized by a more uniform distribution of metabolic pathways, as well as a diverse and well-adapted microbial consortium, have exhibited enhanced stability and outperformed R-Thermo at high-loads. (AU)

• FAPESP's process: 22/01425-4 - Two-stage hydrogen and methane production by the treatment of soybean processing waste (molasses and okara) in thermophilic and mesophilic condition
• Grantee: Isabela Mehi Gaspari Augusto
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 22/05522-4 - Operational viability of an AnSBBR in the treatment of sewage: diclofenac and ibuprofen removal
• Grantee: Ana Paula Paoli
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 22/10615-1 - Consolidation of the biorefinery concept applied to the biological treatment of wastewater and solid wastes
• Grantee: Marcelo Zaiat
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 21/13810-7 - Biofuels production in mesophilic and thermophilic anaerobic conditions by soybean molasses treatment
• Grantee: Giovanna Lovato
• Support Opportunities: Regular Research Grants
• FAPESP's process: 21/13797-0 - Methane production in thermophilic AnSBBR by soybean molasses treatment
• Grantee: Fernanda Furtunato Guerieri
• Support Opportunities: Scholarships in Brazil - Scientific Initiation