ClassNK Grants AiP for Kawasaki, Mitsui E&S’s Clean Ammonia-Fuelled LPG Carrier

Global shipping is feeling the heat to cut emissions, and Japan’s just chalked up a big win in zero-emission technology. On September 8, 2025, ClassNK granted an Approval in Principle (AiP) to a groundbreaking LPG/ammonia carrier design co-created by Kawasaki Heavy Industries and Mitsui E&S. This ship is set up to run on clean ammonia straight out of the gate, all to meet the IMO’s tightening emissions rules.

Right now, maritime transport accounts for about 3% of global CO₂ emissions. The IMO’s plan is bold—halve that figure by 2050 versus 2008 and hit a 20–30% cut by 2030. Sure, heavy fuel oil (HFO) and LNG knock down certain pollutants, but they still belch CO₂. Ammonia, on the other hand, combusts without any CO₂ output—though it does call for extra safety measures to tackle toxicity and NOx formation.

Core Announcement

The AiP covers a medium-range LPG carrier (27,000–65,000 m³) that siphons liquid ammonia right from its cargo tanks into an Ammonia Dual-Fuel Engine. By ditching separate fuel tanks, this setup boosts cargo space and simplifies fuel handling—key for industrial decarbonization. ClassNK’s thumbs-up followed deep dives into 3D structural analysis, risk assessments and its 2024 ammonia-fuelled ship guidelines.

Technical Design and Safety

At its heart, the design revolves around an Ammonia Dual-Fuel Engine with electronic fuel injection fine-tuning ammonia-diesel blends for optimal combustion and lower NOx. A robust after-treatment system—SCR and ammonia slip catalysts—makes sure it nails IMO Tier III limits.

• Cryogenic Fuel Supply: Liquid ammonia stays at –33 °C in double-jacketed stainless steel lines, with pressure-relief valves and burst discs routing any vents into scrubber-equipped zones.
• Boil-off Management: A closed-loop cold box traps and reliquefies boil-off gas, cutting down on fuel loss.
• Safety Systems: Continuous gas detectors, automatic isolation valves and stepped-up ventilation tie into HAZID-based emergency protocols.

The hull plating and piping use materials picked for ammonia’s heft and corrosivity, while crews train on leak drills, personal protective equipment and regular system checks—crucial for safe operation.

Strategic Implications

Securing an AiP is a huge milestone: it kicks off detailed engineering, helps lock in financing and sets the stage for construction. For Kawasaki Heavy Industries—pioneers in marine and industrial systems since 1896—and Mitsui E&S—renowned for propulsion and energy solutions—it cements their role in a potential multi-billion-dollar market for alternative-fuel vessels.

While ammonia bunkering infrastructure is still taking shape, tapping cargo tanks for fuel slashes upfront costs for shipowners. Analysts predict that if ports expand bunkering capabilities, ammonia could capture 10–20% of new alternative-fuel ship orders by the early 2030s—driving forward sustainable energy at sea.

Industry Context

Japan’s deep shipbuilding heritage and massive fertilizer industry give it a head start in ammonia production and fuel applications. In Europe, MAN Energy Solutions and Wärtsilä are trialling ammonia engines, while DNV GL and ClassNK work on harmonizing safety guidelines—signs that global standards are on the horizon. South Korean yards are eyeing retrofits, but Japan’s planned ammonia terminals in Osaka and Nagoya reinforce its home-court edge.

Looking Ahead

The next steps? Nail down detailed engineering and procurement, then move on to sea trials and port tests. If everything falls into place, the first ammonia-fuelled carriers could debut by 2028. At the same time, regulators, ports and insurers will need to update their rulebooks for ammonia bunkering, risk assessments and coverage.

Looking further out, ammonia-fuelled designs might expand into bulk carriers and tankers, even doubling as hydrogen transport—since ammonia can moonlight as a hydrogen carrier. There’s still work to be done on infrastructure and training, but this AiP lays out a clear roadmap toward a low-carbon future at sea.

About the Companies

Kawasaki Heavy Industries, founded in 1896, is a Japanese powerhouse in shipbuilding, aerospace and industrial equipment. Mitsui E&S, rooted in the historic Mitsui Group, specializes in marine engines and energy systems. Their partnership underscores Japan’s drive toward industrial decarbonization and sustainable energy in shipping.