Towards greener shipping: Thermodynamic modelling and feasibility of methanol reforming, CO₂ capture and port-side CO₂ utilisation for UK maritime corridors

This study presents a system-level thermodynamic assessment of green methanol as a low-carbon marine fuel through onboard hydrogen production, proton exchange membrane fuel cell (PEMFC) propulsion, and integrated CO₂ capture and reuse. A steady-state process model is developed in Aspen Plus to simulate methanol steam reforming, hydrogen separation, power generation, and onboard CO₂ liquefaction and storage. Real operational data from two ferry routes, Larne-Liverpool and Immingham-Esbjerg, are used to define realistic power demands and system sizing. The captured CO₂ is transported back to port for reuse in methanol synthesis, forming a closed carbon loop. Cold-energy integration is implemented by using methanol pre-cooled to −80℃ at the port to reduce the refrigeration duty required for CO₂ liquefaction onboard. The proposed system achieves a net propulsion efficiency of 28.4% and an overall end-to-end efficiency of 22.2%. For the Larne-Liverpool route, the system requires approximately 85.7 tonnes of methanol per round trip and produces about 115.1 tonnes of CO₂, corresponding to five methanol tanks and eight CO₂ ISO tanks. For the longer Immingham-Esbjerg route, the storage requirements increase to 11 methanol tanks and 13 CO₂ tanks. A dual-use ISO tank strategy is proposed to reduce onboard storage demand. Overall, the results demonstrate the thermodynamic feasibility and integration potential of methanol-powered shipping with onboard CO₂ capture and reuse.