A closed-loop CCUS-enabled polygeneration system integrating solar energy and biomass for the production of power, hydrogen, and synthetic natural gas

The integration of carbon capture, utilization, and storage (CCUS) into energy systems is a key pathway toward low-carbon energy transition, yet most existing studies treat CO₂ capture and utilization as auxiliary processes and assess system performance under fixed operating conditions. In this study, a fully integrated CCUS-enabled polygeneration system is developed and evaluated to simultaneously produce electricity, hydrogen, and synthetic natural gas (NG) within a closed-loop framework. The proposed configuration integrates a renewable-powered proton exchange membrane electrolyzer, an anaerobic digestion unit for biomass-derived carbon supply, a solid oxide fuel cell (SOFC) for high-efficiency power generation, and multi-stage membrane separation trains for selective hydrogen purification and CO₂ recovery. A comprehensive parametric and scenario-based analysis is conducted to quantify the coupled effects of membrane stage-cut distributions, SOFC current density and inlet temperature, and the fraction of captured CO₂ routed to fuel synthesis. The membrane separation trains achieve hydrogen and CO₂ purities exceeding 99.9% and 95%, respectively, while maintaining acceptable pressure drops. Across eight operating scenarios, the overall energy efficiency varies between approximately 0.30 and 0.46, with total product unit costs ranging from about 33.01–114.5 $/GJ. The lowest specific CO₂ emissions and highest system efficiency are obtained under moderate SOFC current density and optimized membrane operation, whereas maximum net power output is achieved under low pressure-drop conditions. The results identify clear trade-offs among power generation, hydrogen storage, economic performance, and carbon emissions, providing practical design guidelines for optimizing integrated CCUS-based energy systems under realistic operating conditions. • CCUS hub co-produces electricity, H₂, SNG from biogenic CO₂ and wind power. • Membrane trains achieve 99.9% H₂ and 95% CO₂ purities with acceptable pressure drops. • Eight scenarios based on SOFC working conditions and permeator states are analyzed. • System obtains near-zero emissions of 0.001328 kg CO₂/kWh via biogenic CO₂ recycling. • Optimal CO₂ allocation to the SNG unit (0.1–0.4) minimizes both cost and emissions.