Application of a membrane contactor for biogas upgrading via brine-assisted CO2 mineralization: Performance, scaling behavior, and economic feasibility

초록

Global warming, driven by greenhouse gas (GHG) emissions, has emerged as a critical challenge for humanity. CH4 and CO2, which are produced during anaerobic digestion, are subject to strict regulation due to their high global warming potentials. CH4 has the potential to serve as a green energy source. Thus, biogas upgrading to remove CO2 from anaerobic digestion emissions is a promising technology. This study proposes an innovative biogas-upgrading process that integrates a membrane contactor (MC) with brine-assisted CO2 mineralization to selectively remove CO2 and enrich CH4. CO2 removal efficiency was evaluated using synthetic nanofiltration (NF) brine under varying gas flow rates and NaOH concentrations. Carbonate crystals were characterized by morphological and crystallographic analyses under different pH conditions. Furthermore, the effects of carbonate-crystal scaling on performance and the cleaning efficiency were assessed in replicate experiments. Moreover, MC-based biogas upgrading using real NF brine was conducted to confirm its practical applicability. To assess the economic feasibility of the proposed process, costs and profits were estimated for a full-scale module. In conclusion, the proposed process enhances process value by integrating MC-based biogas upgrading with NF brine utilization, and its practical feasibility was demonstrated under realistic operating conditions. Therefore, this study offers a new integrated solution for wastewater treatment by coupling biogas treatment with brine valorization, with strong potential to contribute to environmental engineering through sustainable resource recovery and GHG mitigation.

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