Ammonia (NH₃) is a colorless gas with a pungent odor, highly soluble in water, forming ammonium hydroxide (NH₄OH). In the maritime industry, ammonia is emerging as a potential alternative fuel, driven by the need to reduce greenhouse gas emissions from shipping.

Ammonia benefits from an established global production and distribution network, primarily for agricultural and industrial uses, making it a feasible option for maritime fuel infrastructure. Although its energy density is lower than traditional marine fuels, it is sufficient for long voyages with appropriate storage solutions. Ammonia can be used in internal combustion engines, gas turbines, or fuel cells, and engines compatible with ammonia are under development.

Traditionally, ships have relied on heavy fuel oils, which contribute significantly to environmental pollution. Ammonia offers a cleaner alternative because it does not produce carbon dioxide (CO₂) when burned. Its combustion primarily results in nitrogen and water vapor, although it can emit nitrogen oxides (NOx), which can be controlled with technologies like selective catalytic reduction (SCR).

Adopting ammonia aligns with the International Maritime Organization (IMO) regulations aimed at reducing sulfur oxides (SOx), nitrogen oxides (NOx), and greenhouse gas emissions. Economically, this shift could drive technological innovation and infrastructure development in the maritime sector. However, the transition involves challenges, including the need for new engine designs, retrofitting vessels, and ensuring safe handling due to ammonia's toxic and corrosive nature. Safety is crucial, given ammonia's potential health hazards. Specialized storage, handling systems, and rigorous safety protocols are necessary to prevent exposure and accidents. Despite these challenges, ongoing research and development efforts are optimizing ammonia's use as a marine fuel, improving efficiency, and reducing emissions.