Ammonia - Alternative Fuel Spill Response Considerations Industrial context and risk profile Ammonia is a colourless gas with a strong, irritating odour that is already widely produced, transported and handled in land-based industries, primarily as a fertiliser, and is therefore well established as a marine cargo. Its increasing consideration as a marine fuel reflects its potential to support decarbonisation strategies, as ammonia can offer a zero or near-zero carbon option when produced using renewable energy. At present, however, the majority of global ammonia production relies on fossil-derived hydrogen, resulting in brown or grey ammonia, although decarbonisation pressures are driving a gradual transition toward lower-carbon blue ammonia and fully renewable green ammonia pathways. Ammonia’s appeal is reinforced by a well-established global production and handling infrastructure, and decades of industrial experience. Anhydrous ammonia has a long and generally strong safety record when stored and transported in liquefied form across pipelines, rail networks, ships and road tankers, supported by mature engineering standards and established operational practices. These factors provide a credible foundation for transferring existing technology, operational procedures and safety knowledge into marine fuel applications. Nevertheless, ammonia presents distinct challenges compared with other alternative fuels, particularly due to its high acute toxicity and corrosive properties, and its potential to pose flammability and explosion hazards in enclosed spaces under specific conditions. [1] Regulatory and training developments Since the adoption of the IMO’s initial GHG Strategy in 2018, the regulatory framework supporting ammonia as a marine fuel has progressed, although ammonia propulsion remains at a proof-of-concept stage in 2026. A significant milestone was reached in 2025 with the publication of the IMO’s Interim Guidelines for the Safety of Ships Using Ammonia as Fue