Ammonia as Marine Fuel Poses Lethal Toxicity Risks with No Established Safety Framework

Ammonia (NH3) is emerging as a leading candidate fuel for decarbonizing international shipping because it contains no carbon and can be produced from green hydrogen and atmospheric nitrogen. Major engine manufacturers like MAN Energy Solutions and WinGD are developing ammonia-capable marine engines, and the first ammonia-fueled vessels are expected to enter service by 2026-2027. However, ammonia is acutely toxic to humans at concentrations as low as 300 ppm (15-minute exposure can be fatal), is corrosive to copper and zinc alloys common in marine systems, and produces NOx and potentially nitrous oxide (N2O) during combustion. This matters because a single large container ship would carry 3,000-5,000 tons of ammonia as fuel. An accidental release in a port — where crews, dockworkers, and nearby communities live and work — could create a toxic gas cloud covering several square kilometers. Unlike LNG, which dissipates upward as it warms, ammonia is denser than air and pools at ground level, making evacuations more difficult. The Port of Rotterdam, the Port of Singapore, and other major bunkering hubs are located in or adjacent to densely populated urban areas. The pain is that no comprehensive safety framework for ammonia bunkering exists. The IMO's International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels (IGF Code) does not yet include provisions for ammonia. Classification societies like DNV, Lloyd's Register, and Bureau Veritas are developing interim guidelines, but these are not harmonized. Port authorities are being asked to permit ammonia bunkering operations without established safety distances, leak detection protocols, or emergency response procedures specifically designed for ammonia fuel transfer at the scale required. The structural reason this persists is that maritime safety regulation moves extraordinarily slowly. The IMO typically takes 5-10 years to develop, adopt, and enforce new safety codes. Amendments to the IGF Code for ammonia are not expected to be finalized before 2027-2028 at the earliest, with enforcement potentially not until 2030. Meanwhile, commercial pressure to decarbonize is pushing shipowners to order ammonia-ready vessels now, creating a gap between technological capability and regulatory readiness. In the first place, ammonia was never designed to be a transport fuel. It is an industrial chemical — the world's second-most produced chemical at roughly 185 million tons per year — handled by trained specialists at dedicated chemical plants and terminals. Repurposing it as a ubiquitous marine fuel means exposing a much larger and less specialized workforce (seafarers, port workers, bunkering crews) to its hazards, and the maritime industry's safety culture, while strong, was not built around managing a substance this toxic at this scale.