Project
Results
After four years of collaborative research and innovation, the Ammonia2-4 project concluded on 30 April 2026, delivering valuable insights that support the maritime industry’s transition to low-carbon fuels, focusing on advancing understanding of ammonia as a marine fuel.
Discover below some of the project’s main achievements and technological results.
Four‑Stroke Ammonia Engine Demonstration
A Step Towards Cleaner Shipping
The Ammonia2-4 project has demonstrated that ammonia can be used as a low-carbon fuel in four-stroke marine engines under real operating conditions.
Four-stroke engines are widely used on ships for propulsion and onboard power generation across many vessel types.
Making these engines compatible with ammonia is therefore an important step towards reducing emissions in the maritime sector.
What Did We Achieve?
Through a full-scale laboratory demonstration, the project successfully tested a four-stroke engine running primarily on ammonia.
The engine showed:
• Stable and reliable performance
• High efficiency comparable to LNG operation
• Strong potential for emission reduction
These results confirm that ammonia is a technically viable fuel for marine power generation.
The Demonstration at a Glance
The tests were carried out in May 2025 at the Sustainable Energy Norwegian Catapult Centre, a specialised testing facility in Norway, using a modified Wärtsilä medium-bore engine.
The engine:
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Ran on low-pressure gaseous ammonia as the main fuel
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Used a small amount of diesel for ignition
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Was tested under realistic marine conditions, including different load levels
The engine demonstrated stable and reliable operation across the full load range.
At medium and high loads, ammonia provided over 90% of the total energy.
Watch the Demonstration
See the engine in action and explore key moments from the test campaign:
Significant Emission Reductions
One of the main goals of the project was to understand how much ammonia can reduce emissions.
The results are very promising:
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Up to 88% reduction in greenhouse gas emissions compared to diesel
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Performance maintained under real operating conditions
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Air pollutant emissions controlled through exhaust aftertreatment systems
Safety‑First Design and Operation
Ammonia is a new fuel for shipping, so safety is critical.
The demonstration showed that:
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The system operated according to expectations
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The advanced monitoring systems and safety procedures functioned as planned throughout the test campaign, ensuring safe and controlled operation
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The engine could instantly and safely switch back to diesel if needed
These results confirm that ammonia can be used safely when proper systems are in place.
What Does This Mean for the Future?
The project shows that ammonia can be used in four-stroke engines with limited modifications to existing engine designs.
This opens the door to:
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Cleaner onboard power generation
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Reduced emissions in existing and future vessels
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Further development towards large-scale adoption
Two-Stroke Ammonia Development: Key outcomes
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Improved insight into how ammonia behaves in large marine engines
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The technologies required to inject and manage ammonia safely
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Identification of key technical challenges to address for large-scale adoption
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Clarity on how ammonia fuel systems can be integrated on board ships
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Enhanced understanding of safety procedures and operational practices needed for safe use
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These insights contribute to the long-term development of low-carbon technologies for the maritime sector
While the two-stroke development pathway could not be fully completed within the project timeframe, the activities carried out generated valuable technical knowledge and engineering experience that can support future developments in ammonia-fuelled two-stroke engines.
This provides a strong foundation for the continued development of ammonia-fuelled engine solutions.
These results represent an important step forward, supporting ongoing innovation and helping accelerate the maritime sector’s journey towards decarbonisation.
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