A prospective life cycle assessment framework for sustainable renewable fuels in international shipping: Hydrogen based e fuels

This paper presents a prospective life cycle assessment (pLCA) framework to evaluate the greenhouse gas (GHG) reduction potential of hydrogen-based e-fuels in international shipping. Maritime transport currently contributes approximately 2.89 % of global anthropogenic GHG emissions, with projections indicating a possible increase to 130 % of 2008 levels by 2050. In response, the International Maritime Organization (IMO) aims for net-zero emissions around 2050, necessitating a shift from fossil-based fuels to renewable alternatives. However, concerns persist regarding the life-cycle GHG emissions of such fuels, especially during the well-to-tank stage.

This study develops a pLCA framework that goes beyond conventional attributional or consequential LCA approaches by incorporating future-oriented parameters such as projected transport demand, vessel scrapping rates, and the impact of evolving international regulations (e.g., CII and EEXI). Using a dynamic fleet modeling approach applied to 2062 bulk carriers over 50,000 GT, the study simulates multiple decarbonization pathways and fuel uptake scenarios through 2030, 2040, and 2050. It integrates upstream fuel production emissions—linked to electricity source carbon intensity and technology readiness—with downstream fleet emissions, reflecting regulatory and operational constraints.

The results reveal that while renewable e-fuels such as e-ammonia and e-hydrogen show promising GHG reductions, their effectiveness is highly dependent on the carbon intensity of electricity used in fuel synthesis and on policy-driven adoption rates. The proposed framework offers a reproducible tool for policymakers and shipowners to assess the effectiveness of decarbonization strategies in meeting IMO targets, particularly for import-reliant countries like South Korea.