In-situ biogas upgrading in an anaerobic trickling filter bed reactor treating a thermal post-treated digestate

• Published in: Journal of environmental chemical engineering 2021-12, Vol.9 (6), p.106780, Article 106780
• Main Authors: Thapa, Ajay, Park, Jun-Gyu, Yang, Hyeon-Myeong, Jun, Hang-Bae
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Biogas upgrading; Hydrogen injection; Hydrogenotrophic methanogenesis; Mass transfer; Thermal post-treatment
• ISSN: 2213-3437; 2213-3437
• DOI: 10.1016/j.jece.2021.106780

Digestate, residual organic matter produced as byproducts during the anaerobic digestion process, needs to be utilized because of its potential greenhouse gas emissions. An alternative solution is to valorize digestate for biogas production. The current study investigates feasibility of simultaneous thermal post-treatment of digestate and in-situ biogas upgrading in the trickling filter bed (TFB) reactor. Thermal post-treatment improved the solubilization of food waste-based digestate for biogas production. It was reported that the TFB reactor are efficient to facilitate gas-liquid mass transfer during production of methane (CH4) from carbon dioxide (CO2) and hydrogen (H2). The exogenous H2 injection in in-situ biogas upgrading decreased CO2 content from 51.35% to 16.72% and upgrade CH4 content from 48.65% to 81% in the output gas. The reactor CH4 production rate reached 0.89 L/LR•d and the H2 utilization efficiency of 98% was accomplished. Furthermore, the results showed that chemical oxygen demand removal efficiency of digestate reached to a maximum of 64% in 10 days hydraulic retention time. The microbial analysis indicated hydrogenotrophic Methanobacterium ferruginis was highly abundant in the liquid and biofilm phase, while acetoclastic Methanosarcina flavescens localized in the biofilm phase. The findings from this work showed that digestate can be simultaneously exploited for improving effluent quality and biogas upgrading. [Display omitted] •Trickling filter bed reactor was applied for simultaneous biogas upgrading and digestate treatment.•Simultaneous valorization of CO2 and digestate is feasible in a single-stage trickling filter bed reactor.•Trickling filter bed reactor increased H2 gas-to-liquid mass transfer rate for biogas upgrading.•Exogenous H2 injection led to a maximum of 81% CH4 content in the output gas.•Methanobacterium ferruginis was the most dominant hydrogenotrophic methanogen.