Japan Engine Corporation (J-ENG) has achieved a significant breakthrough in sustainable maritime transport with the completion of the world’s first full-scale commercial ammonia-fueled engine. The innovative 7UEC50LSJA-HPSCR dual-fuel engine was finalized on August 30, 2025, following extensive testing and certification, and is slated for installation on an Ammonia-Fueled Medium Gas Carrier (AFMGC) set to enter commercial service in 2026. This development represents a pivotal step towards reducing greenhouse gas emissions in the global shipping industry.
A New Era for Marine Propulsion: The 7UEC50LSJA-HPSCR Engine
The newly developed 7UEC50LSJA-HPSCR engine boasts a 50-centimeter bore and seven cylinders, capable of operating on both ammonia and heavy fuel oil. This dual-fuel capability is crucial for facilitating a smooth transition to cleaner energy sources in maritime operations. A key feature of the engine is its integrated high-pressure Selective Catalytic Reduction (SCR) system, designed to minimize nitrogen oxide (NOx) emissions, a known challenge with ammonia combustion.
During rigorous performance verification tests conducted at J-ENG’s factory in Akashi, under the supervision of industry leaders including NYK Line, Nihon Shipyard (NSY), Japan Marine United Corporation (JMU), and classification society ClassNK, the engine demonstrated safe and reliable performance. ClassNK subsequently certified its exceptional environmental performance and operational safety.
Significant Environmental Impact and Emissions Control
The successful testing confirmed the engine’s impressive environmental credentials. Emissions trials showed a reduction of more than 90% in greenhouse gases at a 95% ammonia co-firing rate. Critically, after exhaust treatment, virtually no unburned ammonia was released. Nitrogen oxide levels were also approximately half those of conventional heavy oil engines. The thermal efficiency in ammonia operation was reported to be comparable to or even slightly higher than in heavy fuel oil mode.
Ammonia (NH3) is gaining traction as a promising alternative marine fuel because it produces no carbon dioxide (CO2) when combusted. Green ammonia, produced using renewable energy sources, offers the potential for zero “well-to-wake” CO2 emissions, aligning with the International Maritime Organization’s (IMO) 2050 emissions reduction targets.
A Collaborative Development and Future Deployment
This groundbreaking project is a cornerstone of Japan’s ‘Next-Generation Ship Development’ initiative, supported by the Green Innovation Fund and administered by the New Energy and Industrial Technology Development Organization (NEDO). The development involved over 1,000 hours of testing on a single-cylinder prototype between May 2023 and September 2024 at Mitsubishi Heavy Industries’ Nagasaki R&D Centre. This was followed by an additional 700 hours of full-scale engine trials focused on optimizing performance, preventing ammonia leaks, and ensuring crew safety.
The completed engine is scheduled for shipment in October 2025 and will be installed on an Ammonia-Fueled Medium Gas Carrier (AFMGC) currently under construction at JMU’s Ariake Shipyard. This vessel is anticipated to begin commercial service in 2026, marking a historic moment as the first full-scale deployment of an ammonia marine engine.
Key Collaborators Driving Innovation
The consortium driving this project includes:
- Japan Engine Corporation (J-ENG): Developer and manufacturer of the groundbreaking engine.
- NYK Line: A major shipping company involved in the supervision of testing and a key proponent of ammonia as a marine fuel, aiming to complete 15 ammonia-fueled vessels by 2033. NYK Line has also been involved in the world’s first commercial-use ammonia-fueled tugboat, “Sakigake,” which entered service in Tokyo Bay in August 2024 after being retrofitted with an ammonia engine.
- Japan Marine United Corporation (JMU): Shipbuilder constructing the AFMGC that will house the new engine.
- ClassNK: The classification society responsible for certifying the engine’s environmental performance and safety standards.
- Nihon Shipyard (NSY): Another key partner in the project.
Ammonia as a Marine Fuel: Opportunities and Challenges
The maritime industry is under increasing pressure to decarbonize, with the IMO targeting a 70% reduction in greenhouse gas emissions from ships by 2050. Ammonia, as a carbon-free fuel, offers a compelling pathway to achieve these goals.
However, the adoption of ammonia as a marine fuel also presents specific challenges:
- Toxicity: Ammonia is toxic and requires robust safety systems for handling and storage on vessels. The extensive testing by J-ENG focused heavily on leak prevention and monitoring systems to ensure crew and vessel safety.
- NOx Emissions: While ammonia combustion does not produce CO2, it can generate nitrogen oxides (NOx) during the process. The 7UEC50LSJA-HPSCR addresses this with its high-pressure SCR system, which effectively reduces NOx emissions.
- Infrastructure and Production: Scaling up the production of green ammonia and developing the necessary bunkering infrastructure globally will be critical for widespread adoption.
The Path Forward for Zero-Emission Shipping
The completion of J-ENG’s commercial ammonia engine is a pivotal moment, signaling the start of wider-scale adoption of ammonia as a marine fuel. J-ENG is already working on a larger 60-centimeter bore version to accommodate a broader range of ship types and is building a new factory to increase production capacity from 2028, supported by Japan’s GX Economic Transition Bonds.
Other companies like MAN Energy Solutions and Wärtsilä are also actively developing ammonia-fueled engines, highlighting the industry-wide commitment to this alternative fuel. As international regulations for ammonia fuel evolve, the knowledge gained from projects like J-ENG’s will be instrumental in shaping future standards and accelerating the transition to a sustainable, carbon-free shipping industry.
