Towards net-zero: CO2 capture and biogas purification through electric potential swing desorption to achieve SDGs 7 and 13

Abstract

Currently, the potential of biomethane derived from biogas is substantial, positioning it to fulfill a considerable share of the United Kingdom’s total energy needs. The primary challenge associated with raw biogas lies in purifying it to produce biomethane, a process that necessitates the removal of carbon dioxide and hydrogen sulfide. Among the various methods, adsorption of activated carbon (AC) stands out as a particularly effective and cost-efficient approach for converting biogas into biomethane, provided that the regeneration of AC proves economically viable. In this research, a segment of activated carbon was utilized to assess the adsorption properties when exposed to a gas mixture of CO2, H2S, and N2 within a regenerative activated carbon setup. This investigation encompassed the analysis of adsorption and desorption behaviors, process capacities, and the impact of regeneration. To enhance the adsorption of CO2, electro-conductive polymers (ECPs) were incorporated into the AC samples, leading to an extension in breakthrough time. Subsequent to adsorption, the electric potential swing desorption (EPSD) was employed for in situ regeneration of activated carbon samples, involving potentials of up to 30 V. The findings exhibited that the newly introduced EPSD technique considerably diminished desorption durations for both H2S and CO2. Moreover, it successfully rejuvenated the accessible adsorption sites, resulting in reduced desorption times compared to the initial breakthrough time during adsorption. Consequently, the EPSD system proves to be a promising candidate for in situ regeneration of activated carbon to eliminate CO2 and H2S from biogas. Notably, this approach offers inherent advantages over conventional methods including thermal swing adsorption (TSA) and pressure swing adsorption (PSA) in terms of regeneration. The demonstrated method underscores the potential for more efficient and economically viable cycles of adsorption and desorption, thereby enhancing the overall biogas-to-biomethane conversion process to achieve SDGs 7 and 13 for clean and green energy applications.