World’s first ammonia commercial ship engine set to launch in Japan

In a groundbreaking move for maritime transport, Japan Engine Corporation (J-ENG) has unveiled the world’s first commercial ammonia-powered ship engine. This innovative engine, named the 7UEC50LSJA-HPSCR, aims to significantly reduce greenhouse gas emissions in the shipping industry. Officially launched on August 30, the engine represents a major step towards cleaner energy solutions in maritime operations.

Engine Features and Certification

The newly developed engine boasts a 19.6-inch (50 centimeters) bore and seven cylinders, equipped with a high-pressure Selective Catalytic Reduction (SCR) system. This advanced system minimizes nitrogen emissions by utilizing a catalyst and an ammonia-based reducing agent, such as urea, which decomposes into ammonia. Unlike conventional marine engines, this dual-fuel engine can operate on both ammonia and heavy fuel oil, facilitating a smoother transition to sustainable energy sources.

This initiative is part of the ‘Next-Generation Ship Development’ project, supported by the Green Innovation Fund and administered by the New Energy and Industrial Technology Development Organization (NEDO). The engine has undergone rigorous performance testing at J-ENG’s facility, overseen by industry leaders including NYK Line and Japan Marine United Corporation (JMU), along with classification society ClassNK. Following extensive trials in both fuel modes, the engine received certification from ClassNK for its exceptional environmental performance and operational safety.

Scheduled for shipment in October 2025, the engine will be installed on an Ammonia-Fueled Medium Gas Carrier (AFMGC) currently under construction at the JMU Ariake Shipyard. The vessel is anticipated to enter commercial service in 2026, marking a historic milestone as the first full-scale ammonia marine engine deployment.

Extensive Testing and Future Developments

J-ENG’s achievement is the culmination of over 1,000 hours of testing on a single-cylinder ammonia prototype conducted between May 2023 and September 2024 at the Mitsubishi Heavy Industries R&D Center in Nagasaki. Building on these results, the company began testing the full-scale engine in April 2025, logging an additional 700 hours focused on optimizing combustion, preventing leaks, and ensuring ammonia safety.

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The engine is equipped with sophisticated monitoring systems designed to protect crew safety while handling toxic ammonia. Trial data revealed that at full load with 95 percent ammonia co-firing, the engine emitted only three parts per million (ppm) of nitrous oxide (N2O), achieving over a 90 percent reduction in greenhouse gas emissions. Additionally, nitrogen oxide (NOx) emissions were halved compared to traditional oil engines, with virtually zero unburned ammonia emissions, thanks to advanced aftertreatment systems. The thermal efficiency in ammonia fuel operation mode matches or exceeds that of heavy oil operation mode.

Looking ahead, J-ENG is also developing a larger 23.6-inch (60 centimeters) bore ammonia engine to meet the anticipated demand for ammonia-fueled vessels, with operations expected to commence in fiscal year 2028. As a pioneer in next-generation fuel engines, J-ENG aims to enhance Japan’s shipping and shipbuilding industries while contributing to the reduction of greenhouse gas emissions and the pursuit of carbon neutrality by 2050.