World’s first commercial ammonia-fueled engine is here

September 1, 2025, by Naida Hakirevic Prevljak

Japan Engine Corporation (J-ENG) accomplished the first fully functional full-scale commercial ammonia-fueled engine on August 30, 2025.

The engine has been developed as a part of “Next-Generation Ship Development” of the Green Innovation Fund Project administered by New Energy and Industrial Technology Development Organization (NEDO).

The engine official test runs were conducted under the supervision of Nippon Yusen Kaisya (NYK Line), Nihon Shipyard (NSY), Japan Marine United Corporation (JMU) and Nippon Kaiji Kyokai (ClassNK) at J-ENG’s factory from August 27 to 30, 2025. A series of performance verification tests in both ammonia fuel operation mode and heavy fuel oil operation mode as a dual-fuel engine, as well as post-operation inspections of major components, were successfully completed, and the engine’s “outstanding environmental performance and safety” were certified by ClassNK.

As informed, the engine will be shipped in October 2025 and then installed on an ammonia-fueled medium gas carrier being constructed by JMU Ariake Shipyard. The vessel is scheduled to enter service in 2026.

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J-ENG previously conducted approximately 1,000 hours of test runs on a single-cylinder ammonia-fuel test engine at the Mitsubishi Heavy Industries Research & Development Center at Nagasaki between May 2023 and September 2024.

Using the results and insights gained from the test, J-ENG manufactured the first full-scale commercial engine 7UEC50LSJA-HPSCR and began test runs on ammonia fuel in April 2025. Subsequently, over five months, the engine underwent meticulous testing for a total of 700 hours. This period focused on optimizing various performance aspects while concurrently confirming high reliability and safety features, including leak prevention and monitoring systems for toxic ammonia.

The engine was thus completed, equipped with sufficient functionality to ensure the safe operation of actual vessels and the safety of crew members.

“J-ENG is extremely pleased and proud to be able to deliver to customers ahead of the rest of the world this safe and reliable engine, the result of a meticulously planned, long-term development program that accumulated extensive operational data over an extended period,” the company said.

Trial run data for this engine shows that at 100% load and a 95% ammonia co-firing rate, nitrous oxide (N₂O) emissions are approximately 3ppm, achieving a reduction of over 90% in greenhouse gas (GHG) emissions. Nitrogen oxide (NOx) emissions were confirmed to be approximately half those of heavy oil engines, with unburned ammonia emissions virtually zero (post-NOx SCR). It has also been confirmed that the thermal efficiency in ammonia fuel operation mode is equivalent to or higher than that in heavy oil operation mode.

Following from the first engine mentioned above (bore 50cm), J-ENG is also concurrently developing an ammonia-fueled engine with 60cm bore to address the wide variety of ammonia-fueled ships expected to emerge in the future market, and is actually working on several promising follow-on projects.

Furthermore, after achieving the development and social implementation of these engines, JENG is proceeding with the construction of a new factory with support from a subsidized project jointly run by the Ministry of the Environment and the Ministry of Land, Infrastructure, Transport and Tourism using GX Economic Transition Bonds in order to expand the production volume of ammonia fuel engines in a product mix with heavy oil engines and further promote the spread of zero-emission ships. The new factory is scheduled to commence operations in fiscal year 2028.

As a first mover in next-generation fuel engines, J-ENG intends to contribute to the development of Japan’s shipping and shipbuilding industries by promoting the early market introduction and widespread adoption of those engines, while also contributing to the reduction of greenhouse gas emissions in the shipping industry and the realization of carbon neutrality by 2050.