J-ENG builds ‘world’s first’ commercial-ready ammonia-fuel maritime engine

Team members with new J-ENG ammonia-fuel engine (Photo: J-ENG)

Japan Engine Corporation (J-ENG) has completed assembly of what is described as the world’s first full-scale ammonia-fuel commercial maritime engine.

The 7UEC50LSJA-HPSCR seven-cylinder engine (50 cm bore) has been developed as a part of the ‘Next-Generation Ship Development’ Green Innovation Fund project.

Test runs of the engine were carried out in late August this year, witnessed by Nippon Yusen Kaisya (NYK Line), Nihon Shipyard, Japan Marine United Corporation and Nippon Kaiji Kyokai.

Performance verification tests were carried out using both ammonia fuel and heavy fuel oil; the engine is classified as a dual-fuel model. Environmental and safety performance was certified by ClassNK.

J-ENG reported that the engine will be shipped in October 2025 for installation on an AFMGC (Ammonia-Fuelled Medium Gas Carrier) under construction at JMU Ariake Shipyard. The vessel is scheduled to enter service in 2026.

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, the engine underwent for a total of 700 hours over a five-month period. This focused on optimizing various performance aspects while concurrently confirming high reliability and safety features, including leak prevention and monitoring systems for toxic ammonia.

Trial run data for the engine shows that at 100% load and a 95% ammonia co-firing rate, nitrous oxide emissions are approximately 3 ppm, achieving a reduction of over 90% in GHG emissions.

Nitrogen oxide (NOx) emissions were confirmed to be approximately half those of heavy oil engines, with virtually zero unburned ammonia emissions (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.

J-ENG is also concurrently developing an ammonia-fuel engine with a 60 cm bore to address the wide variety of ships expected to use the tech.