Purification of Methane Through Hydrogenotrophic Methanogenesis in Thermophilic Anaerobic Conditions Under Different Pressures

Abstract

In response to challenges resulted from climate change, governments worldwide have committed to achieving net-zero carbon emissions by 2050. Carbon capture, utilization, and storage (CCUS) technologies can reduce atmospheric greenhouse gases, thus facilitating the achievement of carbon neutrality or negative emissions. Hydrogenotrophic methanogenesis enables the conversion of CO2 and H2 into CH4, which can increase biogas’ methane concentration to higher than 95%, thereby making biogas suitable for natural gas grids and facilitating the achievement of carbon neutrality. The present study employed hydrogenotrophic methanogens in a laboratory-scale trickling biofilter reactor (TBR) to convert hydrogen and carbon dioxide into methane, with the aim to enhance the methane concentration of biogas from 60%–70% to over 90%, thereby meeting standards for natural gas. The rates of CO2 and H2 utilization were assessed to determine the feasibility of the aforementioned method for CCUS in practical applications. When the TBR was operated under thermophilic conditions at atmospheric pressure, with the gas retention time (GRT) fixed at 2 h, it produced biogas with an average methane concentration of 87% and had a methane conversion rate of 84.71%. By comparison, when the TBR was operated under thermophilic and pressurized conditions under the same GRT, it produced biogas with an average methane concentration of 95% and had a methane conversion rate of 88.30%. Thus, the results of this study indicate that a TBR can achieve optimal methane conversion under thermophilic and high-pressure conditions.

Keywords: hydrogenotrophic methanogenesis, carbon capture, utilization, and storage (CCUS), trickling biofilter reactor (TBR), thermophilic, pressurized