Maritime regulations governing hydrogen fuel shipping are evolving rapidly as the global energy transition accelerates. The International Maritime Organization (IMO) plays a central role in establishing safety codes, operational guidelines, and infrastructure standards for hydrogen-derived fuels, particularly liquid hydrogen (LH2) and ammonia. These regulations address the unique challenges posed by hydrogen’s low density, flammability, and cryogenic requirements, as well as ammonia’s toxicity and corrosiveness. Regional adaptations, such as Singapore’s bunkering guidelines, further refine these frameworks to accommodate local infrastructure and operational conditions.

The IMO’s International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels (IGF Code) provides the foundational framework for hydrogen shipping. Initially developed for liquefied natural gas (LNG), the IGF Code has been expanded to include hydrogen-specific provisions. For LH2 carriers, the code mandates double-walled cryogenic tanks with vacuum insulation to minimize boil-off gas and prevent structural failure at temperatures as low as -253°C. Materials in contact with hydrogen must undergo rigorous testing for embrittlement, and gas detection systems must be installed to monitor leaks. Ventilation systems are required to disperse hydrogen vapors, which are lighter than air but pose explosion risks at concentrations as low as 4% in air.

Ammonia transport regulations are governed by the IMO’s International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code). Ammonia, a common hydrogen carrier due to its high energy density and established transport infrastructure, is classified as a toxic and corrosive substance. The IBC Code requires specialized containment systems, including corrosion-resistant coatings and secondary barriers to prevent leaks. Crew training must include emergency response procedures for ammonia exposure, which can cause severe respiratory damage at concentrations above 25 ppm. Unlike hydrogen, ammonia vapors are denser than air, necessitating different ventilation and dispersion strategies.

Port infrastructure standards for hydrogen and ammonia bunkering are still under development, but the IMO’s Guidelines for the Safety of Ships Carrying Liquefied Gases in Bulk provide interim guidance. These include requirements for dedicated loading/unloading arms with emergency release systems, exclusion zones during operations, and compatibility assessments between ship and shore systems. Singapore, a leader in maritime fuel transition, has introduced additional bunkering guidelines for hydrogen-derived fuels. The Maritime and Port Authority of Singapore (MPA) mandates real-time monitoring of gas concentrations during transfer operations and requires bunkering vessels to undergo third-party audits for compliance with IGF and IBC Codes.

Regional adaptations of IMO regulations reflect local priorities and infrastructure capabilities. The European Union’s Alternative Fuels Infrastructure Regulation (AFIR) sets binding targets for hydrogen refueling points in major ports by 2030, aligning with the IMO’s decarbonization goals but adding stricter reporting requirements. Japan’s Clean Energy Marine Initiative focuses on ammonia bunkering, leveraging existing LNG infrastructure while addressing toxicity risks through enhanced crew training and leak detection. In contrast, the United States prioritizes LH2 transport for its space program, with the Coast Guard enforcing additional cryogenic safety measures under 46 CFR Part 154.

The IMO’s role in harmonizing these regional approaches is critical. Its Marine Environment Protection Committee (MEPC) is developing a lifecycle emissions framework for hydrogen-derived fuels, which will influence future regulations on well-to-wake emissions. Preliminary discussions suggest that ammonia produced from renewable hydrogen may receive preferential treatment under the Carbon Intensity Indicator (CII) regulations, while LH2 carriers will need to demonstrate low boil-off rates to qualify as zero-emission vessels.

Technical challenges remain in standardizing hydrogen fuel shipping. LH2 carriers require larger storage volumes than conventional fuels, impacting vessel design and port storage capacity. Ammonia’s toxicity complicates crew safety protocols, particularly in congested shipping lanes. The IMO is addressing these issues through working groups on alternative fuels, with input from classification societies like DNV and Lloyd’s Register. These groups are evaluating proposals for standardized pressure-relief systems, emergency shutdown procedures, and bunkering checklists.

Port authorities are also adapting to hydrogen shipping. Rotterdam’s H2Gate project includes a dedicated LH2 import terminal with cryogenic pipelines, while Yokohama’s Green Ammonia Bunkering Initiative focuses on ammonia-to-power systems for docked vessels. Both projects align with IMO guidelines but incorporate local safety margins, such as larger exclusion zones during bunkering or additional pilotage requirements for hydrogen carriers entering busy harbors.

Future regulatory developments will likely focus on scaling infrastructure. The IMO is expected to release updated IGF Code provisions for large-scale LH2 transport by 2025, including standardized tank designs and boil-off gas recovery systems. Ammonia regulations may evolve to address blending with hydrogen or other carriers, with preliminary discussions already underway at the International Association of Classification Societies (IACS). Regional hubs like Singapore and the EU are anticipated to pilot these updates before global adoption.

The interplay between international standards and regional implementations creates a complex but necessary framework for hydrogen fuel shipping. As the IMO refines its codes and regional authorities test localized adaptations, the maritime industry is gradually building a safety-centric ecosystem for hydrogen-derived fuels. This regulatory evolution is essential to support the shipping sector’s transition to zero-emission energy sources while maintaining operational reliability and crew safety.