Viability and Impacts of Low-carbon Fuels for Maritime Applications

Abstract This study evaluates the lifecycle viability of ammonia, hydrogen, methanol, and Fischer–Tropsch diesel as low-carbon fuels for maritime shipping by integrating regional supply chain modeling with the NavigaTE global fleet model. Using this framework, we consider scenarios involving widespread adoption of single alternative fuels and production pathways to illustrate the big-picture advantages and disadvantages of each in the context of the global maritime industry. Production pathways that use renewable electrolytic or biogenic hydrogen offer the most favorable trade-offs between costs and emissions in most regions, achieving up to 90% and 80% reductions in well-to-wake emissions relative to low-sulfur fuel oil, respectively. However, each comes with substantial feedstock constraints. Electrolytic fuels require up to 6,800 TWh/year of electricity, equivalent to 23% of current global generation. Biogenic routes demand up to 1.6 Gt of lignocellulosic biomass, exceeding estimated sustainable availability from forestry residues. Blue hydrogen pathways that pair methane reforming with carbon capture and storage can reduce emissions below LSFO levels if sequestration is permanent, but require up to 24% of global natural gas supply and come at higher cost than electrolytic and biogenic options in many regions. Methanol and FT diesel production also necessitate large CO2 inputs – up to 580 Mt and 1,300 Mt, respectively, which would require a major scale-up of carbon capture and utilization. Emissions and costs vary by up to a factor of ten depending on the production region, with the most viable options concentrated in countries offering low-cost, low-carbon electricity or natural gas. INTRODUCTION Maritime shipping is the backbone of global trade, carrying over 80% of international cargo while contributing roughly 3% of global greenhouse gas (GHG) emissions (IMO 2021). Today, the sector relies almost entirely on fossil fuels to meet its energy needs (IEA 2023), making decarbonization both an urgent priority and a formidable challenge. In recognition of this, the International Maritime Organization (IMO) has approved a regulatory framework designed to achieve net zero emissions in the shipping industry by or around 2050, helping to catalyze research and investment into alternative fuels and propulsion systems (IMO, 2025).