The HyMethShip project is developing the first internal combustion engine for marine propulsion system capable of CO2 emission reduction of more than 95%. The project will achieve this goal by using renewable methanol as the energy carrier and implementing pre-combustion carbon capture. The system will be demonstrated onshore at full scale. The HyMethShip system innovatively combines a membrane reactor, a CO2 capture system, a storage system for CO2 and methanol, as well as a hydrogen-fuelled combustion engine into one system. The proposed solution reforms methanol to hydrogen, which is then burned in a reciprocating engine that has been upgraded to burn multiple fuel types and is specifically optimised for hydrogen use. The new concept allows for a closed CO2 loop ship propulsion system while maintaining the reliability of well-established marine engine technology. The HyMethShip project will undertake risk and safety evaluations, as well as life cycle costing (LCC) and life cycle assessment (LCA) to ultimately optimise economic and environmental performance for different ship types and operating scenarios.