Decarbonizing potential of global container shipping with hydrogen-based fuels

Abstract

Hydrogen-based fuels are expected to support maritime shipping in reaching net-zero climate targets. However, the complexity of hydrogen-based fuel supply, propulsion system deployment, and fleet composition make their full life cycle decarbonization potential unclear. A comprehensive fleet-level assessment of their decarbonization potential is thus essential. Here, we evaluate the life cycle climate change impact of global container shipping using hydrogen-based fuels from 2020 to 2050, considering fuel mix, propulsion system, ship size and transport demand. By integrating energy scenarios from the International Energy Agency with socio-economic scenarios from the Shared Socioeconomic Pathways and the Organization for Economic Co-operation and Development, we explore three scenarios that represent different levels of ambition for the future hydrogen production transition, hydrogen-based fuel use, and corresponding transport demand: the Less Ambitious, Ambitious and Very Ambitious scenarios. Our findings indicate that container shipping's greenhouse gas (GHG) emissions per tonne-nautical mile could decrease from 22 g CO₂-eq in 2020 to 21 g, 9 g, and 3 g CO₂-eq by 2050 under the Less Ambitious, Ambitious, and Very Ambitious scenarios, respectively. Cumulative GHG emissions from global container shipping could reach 9–12 Gt, 7–10 Gt, and 4–5 Gt CO₂-eq between 2020 and 2050 across these scenarios, accounting for 1–3% of the global carbon budget required to achieve the worldwide net-zero target. The substitution of heavy fuel oil with hydrogen-based fuels does not always lead to a reduction in GHG emissions: in the Less Ambitious scenario, cumulative emissions increase by 0.4–0.6 Gt CO₂-eq due to the slow decarbonization in hydrogen production, whereas in the Ambitious and Very Ambitious scenarios, they decline by 1–2 Gt and 3–5 Gt CO₂-eq, respectively. Deep decarbonization of maritime shipping requires overcoming key bottlenecks in renovating the fleet, scaling up ammonia production and electrolyzer capacity, and ensuring sufficient renewable electricity supply. This highlights the need for coherent policies to foster multi-sectoral coordination among maritime shipping, hydrogen-based fuel production, and power generation to maximize their decarbonizing potential.