Methane (CH₄) is a potent greenhouse gas, and the mitigation and high-value utilization of low-concentration CH₄ remain challenging due to the lack of cost-effective and environmentally sustainable separation materials. Coal-tar phenolic oil, an underutilized industrial by-product, offers a promising carbon resource for the development of porous adsorbents. This study aims to develop a resource-efficient strategy for converting coal-tar phenolic oil into high-performance ultramicroporous activated carbons (POACs) for CH₄ enrichment and to systematically evaluate their environmental and economic performance.
A synergistic alkali extraction and in situ ion activation strategy was developed to regulate the ultramicropore structure of POACs. Ion exchange enabled the molecular-level distribution of active species, while optimization of the KOH dosage allowed precise control over the ultramicropore size distribution. The optimized POAC-0.5-600 achieved a CH₄/N₂ selectivity of 7.92, exceeding the reported performance of conventional coal-based porous carbons. Notably, the proposed synthesis reduced KOH consumption by 77-93% compared with conventional activation methods, thereby decreasing chemical consumption and acidic wastewater generation during adsorbent preparation. These results demonstrate that enhanced CH₄/N₂ separation can be achieved while simultaneously improving the resource efficiency of the synthesis process.
To further assess the practical sustainability of the developed adsorbent, a full life-cycle assessment was established for the integrated “adsorbent synthesis–CH₄ enrichment–power generation” value chain. The system achieved carbon neutrality within 19-38 days, while techno-economic analysis yielded a carbon reduction cost of only 18.55 USD t^-1 CO₂, below the U.S. Department of Energy benchmark of 30 USD t^-1 CO₂ for 2030. Overall, this study establishes an integrated pathway combining waste-resource valorization, ultramicropore engineering, CH₄ enrichment, and low-carbon energy utilization, providing a promising approach for the sustainable mitigation and utilization of low-concentration CH₄.
 

Coal-based porous carbon; In situ ion activation; Pore structure regulation; Life cycle assessment; Sustainable resource utilization pathways