J-ENG Tests World’s First Full-Scale Commercial Clean Ammonia Marine Engine

It’s a big moment for clean ammonia adoption—Japan Engine Corporation (J-ENG) has just wrapped up testing the world’s first full-scale commercial dual-fuel ammonia engine. Funded by Japan’s Green Innovation Fund under NEDO and certified by ClassNK, this 7-cylinder, 50 cm bore powerhouse is heading out for shipment in October 2025 and will slide into service on a medium gas carrier at JMU’s Ariake Shipyard in 2026.

Key Facts at a Glance

• Who: J-ENG, a joint venture of Mitsui E&S Machinery, Mitsubishi Heavy Industries and Kawasaki Heavy Industries, with partners NYK Line, Nihon Shipyard (NSY) and Japan Marine United (JMU).
• What: First commercial-scale dual-fuel ammonia engine, designed to run on ammonia or heavy fuel oil seamlessly.
• Where: Trials at J-ENG’s Sasebo facility and MHI’s Nagasaki R&D Centre; installation at JMU Ariake Shipyard, Japan.
• When: Full-scale tests Aug 27–30, 2025; shipment in Oct 2025; vessel goes live in 2026.
• Why it matters: Cuts greenhouse gas emissions by over 90%, halves NOx versus conventional engines and slashes unburned ammonia nearly to zero—paving the way for industrial decarbonization and a shift toward zero-emission technology in shipping.

Milestone Tests

Over four straight days at the end of August, the ammonia engine clocked 1,700 trial hours under different loads. Engineers kept tabs on emissions, performance and safety systems—everything from leak detection to post-combustion Selective Catalytic Reduction (SCR). ClassNK’s certification team was on hand to verify maritime safety and environmental compliance, confirming:

• Greenhouse gas cuts: More than 90% reduction in CO₂-equivalent when firing at high ammonia co-firing rates.
• NOx emissions: Roughly 50% lower than heavy fuel oil operation.
• Ammonia slip: Virtually zero, thanks to optimized SCR and continuous exhaust monitoring.
• Thermal efficiency: On par with or slightly exceeding performance on heavy oil.

Technical Highlights

The 7-cylinder setup with a 50 cm bore hits a sweet spot between power density and operational flexibility. Here’s the scoop on its key systems:

• Dual-fuel injection: Seamlessly switches between ammonia and heavy fuel oil to keep uptime high during bunkering or fuel transitions.
• Advanced SCR: Converts NOx and trace ammonia into harmless nitrogen and water, meeting IMO Tier III rules and eyeing future zero-emission technology standards.
• Comprehensive safety suite: Redundant leak detectors, inerting systems and rigorous operator training to manage ammonia’s toxicity safely.

Testing unfolded at J-ENG’s Sasebo plant and MHI’s Nagasaki R&D Centre, tapping decades of marine engine know-how. J-ENG’s founding partners pooled R&D resources, with NEDO’s funding covering a sizable share under its Next-Generation Ship Development program.

Strategic and Industry Impact

This isn’t just a shiny new prototype—it marks a major pivot in investment and regulation. Big players like NYK Line are already queuing up for ammonia-fired vessels, and shipyards such as NSY are gearing up for these next-gen designs. But don’t forget the infrastructure: ports will need dedicated ammonia storage tanks, specialized transfer systems and revamped safety protocols. Feasibility studies are already buzzing in Japan, Singapore and northern Europe.

On paper, ammonia burns carbon-free, but its true climate impact depends on how it’s made. The star of the show? Green ammonia—produced via renewable-powered electrolysis—so you nail low upstream emissions. Next up for J-ENG: a larger 60 cm bore ammonia engine for ULCCs and bulk carriers, plus a new 2028 factory to mass-produce both ammonia and heavy fuel oil variants, driving forward industrial decarbonization.

Looking Ahead

Installation kicks off in late 2025 at JMU’s Ariake Shipyard, with the carrier set to sail in 2026. Industry watchers will be glued to metrics like bunkering turnaround, real-world uptime and operational data. If the engine hits its lab numbers, regulators could fast-track ammonia production rules and boost adoption of zero-emission technology in maritime transport.

You don’t have to squint to see the bigger picture: this milestone propels the industry from pilot projects into commercial reality. With policymakers chasing ambitious industrial decarbonization and sustainable energy goals, clean ammonia just might be the breakthrough shipping needs—if supply chains and safety protocols can keep pace.

About J-ENG
Founded in 2017, Japan Engine Corporation is a joint venture of Mitsui E&S Machinery, Mitsubishi Heavy Industries and Kawasaki Heavy Industries. Specializing in marine dual-fuel engines, J-ENG leads R&D into ammonia and heavy fuel oil propulsion, backed by government-supported green shipping initiatives.