The potential of ammonia as fuel

Ammonia holds great potential as a sustainable fuel, particularly in industries such as shipping, where its ability to fuel engines directly or to be converted into hydrogen offers a promising path to reducing emissions. This versatile gas could play a significant role in the future energy landscape. Here is what you need to know.

Ammonia (NH₃) is a colourless gas made up of nitrogen and hydrogen, commonly used in cleaning products, refrigeration systems and fertilisers. While not a potent greenhouse gas like carbon dioxide (CO₂) or methane (CH₄), the production and use of ammonia can indirectly contribute to greenhouse gas emissions.

Traditional ammonia production relies on fossil fuels. This leads to significant CO₂ emissions and the end product is referred to as “brown” or “grey” ammonia. “Green” ammonia has the same chemical makeup, but because it is produced using renewable energy sources, it is entirely emission free. The global green ammonia market is expected to see an annual growth rate of 116 per cent from 2024 to 2030.

Ammonia fuel cells convert ammonia into electricity by splitting it into nitrogen and hydrogen through a process called “cracking”. The hydrogen produced is then used in the fuel cell to generate electricity.

Hydrogen is difficult to store. Being the lightest molecule, the gas has a low density so it must be kept under high pressure or at temperatures below –253 degrees (cryogenic temperatures). The need to maintain these conditions means that the gas is not feasible as a fuel for transport over great distances.

Ammonia, on the other hand, can be easily liquefied at low pressures, making it more practical for transportation. Once delivered, ammonia can be converted into hydrogen at the point of use, allowing for a decentralised hydrogen production system.

Ammonia fuel cells are particularly promising for the maritime industry, where reducing CO₂ emissions is crucial. A notable example is the first ship, Viking Energy, equipped with an ammonia-based fuel cell, designed by Norwegian pioneer SEAM. The vessel has achieved an impressive 30 per cent reduction in emissions. 

The first examples of ammonia-fuelled engines are showing great promise. One such case is Wärtsilä 25, which became the first commercially available four-stroke ammonia engine in late 2023. The technology not only focuses on emission reductions, but also on ensuring safety in terms of ammonia’s toxicity and flammability. The engine will be installed on a vessel that will service Equinor’s offshore platforms in Norway.

Another company at the forefront of ammonia propulsion is Man Energy Solutions. It is currently developing the world's first two-stroke ammonia marine engine, with a goal of cutting greenhouse gas emissions by more than 90 per cent compared with an engine running on fuel oil. The first commercial engine is expected to be installed in 2025. 

Yara Eyde, to be delivered in mid-2026, will be the world’s first containership powered by pure ammonia. The vessel will operate between Norway and Germany, delivering fertiliser and enabling the emission-free import of goods back to Norway. This new shipping service will reduce Yara’s Scope 3 emissions by 11 000 metric tons of CO₂ per year. Yara Clean Ammonia will deliver fuel to the vessel via a bunkering solution that is being developed with support from Innovation Norway and Enova.

Ammonia is playing a key role in the global transition to carbon-neutral energy. Part of its appeal is that supply chain infrastructure is already in place for production, transportation and utilisation at large scale. In the maritime sector, the adoption of ammonia-fuelled technology is viewed as crucial to reducing emissions. That's good news for both the industry and the environment.