E-fuels for maritime decarbonisation: a well-to-wake life cycle perspective on pathway readiness and policy alignment.

Abstract

International shipping faces a critical decarbonisation challenge, with lifecycle greenhouse gas (GHG) emissions continuing to rise despite efficiency improvements and projected to grow substantially without intervention. This paper evaluates the viability of alternative maritime fuel pathways through a systematic well-to-wake (WtW) life cycle assessment (LCA), examining ammonia, methanol, hydrogen, and power-to-liquid fuels across a range of production routes. Results reveal substantial intra-pathway variability, with only fuels derived from low-carbon electricity and rigorously controlled carbon inputs consistently achieving intensities compatible with long-term decarbonisation targets. The analysis identifies a structural misalignment between empirical evidence and existing policy frameworks, which continue to rely in part on tank-to-wake (TtW) accounting. This misalignment risks incentivising fuel pathways that are formally compliant but environmentally ineffective, leading to inefficient capital allocation and potential technological lock-in. The paper argues for the adoption of quantitative WtW GHG intensity thresholds as the foundation of maritime fuel regulation, replacing reliance on categorical "colour" taxonomies. Beyond lifecycle emissions, the paper introduces a novel analysis of the geographical concentration of e-fuel production. Emerging supply chains are increasingly clustered in regions with low-cost renewable resources, creating a divergence between the locations of fuel production and regulatory demand, particularly in Europe and the UK. This raises critical concerns regarding lifecycle emissions from transport, the externalisation of industrial value, and the potential reconfiguration of global energy dependencies. The findings demonstrate that maritime decarbonisation is a systems-level challenge spanning emissions accounting, industrial strategy, and energy security. Effective policy must therefore integrate robust WtW methodologies with interventions that address supply chain geography and support the development of domestic e-fuel production capacity.