Japan Engine Corporation (J-ENG) claims to have completed the world's first commercial ammonia-fueled engine, marking a potential advance in maritime decarbonization technology.

The company said its 7UEC50LSJA-HPSCR engine — featuring a 50 cm bore and seven cylinders with high-pressure selective catalytic reduction — completed official test runs on August 30 at J-ENG's factory. The testing was conducted under supervision from Nippon Yusen Kaisha (NYK Line), Nihon Shipyard Co., Japan Marine United Corporation (JMU) and classification society Nippon Kaiji Kyokai (ClassNK).

According to J-ENG, the dual-fuel engine underwent performance verification tests in both ammonia fuel and heavy fuel oil operation modes, with ClassNK certifying its environmental performance and safety features.

The engine is scheduled for shipment in October and installation on an ammonia-fueled medium gas carrier under construction at JMU Ariake Shipyard, with the vessel expected to enter service in 2026.

J-ENG said it conducted approximately 1,000 hours of testing on a single-cylinder ammonia-fuel test engine at Mitsubishi Heavy Industries Research & Development Center in Nagasaki between May 2023 and September 2024. The company began testing the full-scale commercial engine on ammonia fuel in April 2025, accumulating 700 hours of testing over five months.

The development forms part of the "Next-Generation Ship Development" program under the Green Innovation Fund Project, administered by Japan's New Energy and Industrial Technology Development Organization (NEDO).

Trial data indicates that at 100% load and 95% ammonia co-firing rate, nitrous oxide emissions were approximately 3 ppm, representing what J-ENG claims is a reduction of over 90% in greenhouse gas emissions compared to conventional engines. The company said nitrogen oxide emissions were approximately half those of heavy oil engines, with unburned ammonia emissions virtually zero after selective catalytic reduction treatment.

J-ENG said thermal efficiency in ammonia fuel operation mode was equivalent to or higher than heavy oil operation mode.

The company is concurrently developing a 60 cm bore ammonia-fueled engine and is constructing a new factory with government support to expand production capacity. The facility is scheduled to commence operations in fiscal year 2028, utilizing funding from GX Economic Transition Bonds through a joint project by Japan's Ministry of the Environment and Ministry of Land, Infrastructure, Transport and Tourism.

J-ENG said it aims to contribute to greenhouse gas emission reductions in the shipping industry and support Japan's carbon neutrality target by 2050 through early market introduction of ammonia-fueled engines.