Navigating toward 2050 decarbonization: A design-constrained life cycle emission and costs assessment for sustainable marine fuel retrofits incorporating feedstock sources

Abstract

Abstract

This study contributes to the maritime industry's pathway toward the IMO 2050 net-zero objective through an integrated approach that links design-constrained retrofit evaluation and fuel feedstock sources with life-cycle and cost assessments. Two representative vessels, a 49 m Ro-Ro ship operating on medium range routes and an 87 m car ferry operating on longer routes, are evaluated, with propulsion configurations divided into ICE systems and electric motor systems. Retrofit scenarios include electric propulsion using lithium-ion batteries and hydrogen fuel cells, and ICE propulsion operating on methanol and ammonia, both recognized for their potential to deliver low or near-zero carbon emissions. Environmental performance is assessed through a well to wake life cycle assessment, while the cost analysis incorporates feedstock sources to evaluate long-term cost feasibility under future decarbonization pathways. The retrofit feasibility assessment shows that all alternatives except pure battery-electric propulsion are technically achievable, with battery energy density as the limiting factor. From a life cycle perspective, hybrid diesel–electric propulsion, fossil based hydrogen fuel cells, fossil based ammonia ICE, and renewable energy based methanol ICE offer viable mid-term mitigation options, while only renewable energy based ammonia and renewable energy based hydrogen enable net zero decarbonization consistent with long-term climate objectives. Integrating retrofit feasibility, environmental performance, and cost assessment, the study highlights ammonia-based ICE systems as particularly promising solutions for achieving IMO 2050 targets, offering both technical feasibility and economic robustness under time horizon and scenario of this study.