Technoeconomic and Environmental Assessments of CO₂ Methanation and Liquefaction for Climate Mitigation

Climate change driven by significant anthropogenic greenhouse gas emissions necessitates accelerating the decarbonization of the energy system. The power-to-X strategy has emerged as a promising pathway to convert renewable electricity into carbon-neutral energy carriers. Synthetic natural gas is an attractive solution due to its compatibility with existing natural gas infrastructures and widespread end-use applications. In this work, a technoeconomic and environmental analysis of liquefied synthetic natural gas production via CO₂ methanation is conducted. The analysis focuses on evaluating the economic feasibility and environmental impact of the methane derived from green H₂ and captured CO₂ in multiple renewable electricity supply scenarios as well as future cost-reduction pathways. Such feasibility indicators are systematically assessed in different renewable electricity supply scenarios to investigate the climate mitigation potential. The assessment is conducted within a cradle-to-gate system boundary covering the production, liquefaction, and storage of synthetic natural gas, with conventional fossil-based natural gas used as the baseline for comparison. The results demonstrate that power-to-methane can show a wide cost range (76.0 to 109.0 $ GJ^-1), which is dependent on electricity prices. Further, it can achieve competitive environmental performances (approximately 0.015 tonCO₂-eq GJ^-1) and represents a feasible alternative to fossil-based natural gas under favorable renewable electricity integration. This study highlights the potential role of synthetic natural gas as a sustainable energy carrier for long-term climate mitigation.