ClassNK approves novel ammonia-fuelled bulker with ‘world-first’ type B fuel tank on stern deck

ClassNK has issued approval in principle (AiP) for an ammonia-fuelled Panamax bulk carrier design featuring a newly developed IMO type B independent fuel tank.

Engineered by Japan’s Planning and Design Center for Greener Ships (GSC), the design represents the world’s first AiP for a vessel with type B tanks installed on an exposed stern deck, according to the Tokyo-based class society.

As the maritime industry grapples with the urgent challenge of decarbonisation, ammonia is seen as a frontrunner among zero-carbon fuels. While cylindrical IMO type C tanks have long been the industry standard due to their cost-effectiveness, the requirement for large-capacity storage is shifting the focus towards type B designs.

The type B design is said to represent a safer alternative to the type A tanks used for LPG, utilising exhaustive fatigue analysis to minimise leakage. Crucially, its rectangular geometry ensures greater volumetric efficiency than cylindrical type C alternatives. As it can be manufactured without dedicated facilities, the design allows operators to circumvent the supply chain bottlenecks and long lead times typical of the type C market.

The Panamax bulker complies with the IMO’s provisional safety guidelines for ammonia-fuelled vessels (MSC.1/Circ.1687), confirming the design’s feasibility from both a regulatory and safety perspective.

This latest certification follows previous AiPs granted to GSC by ClassNK, including a 2022 approval for an ammonia-fuelled bulk carrier and a 2024 approval for a prismatic fuel tank for container ships.

Established in 2020, GSC serves as a collaborative hub for Japanese shipbuilders and partners, aiming to accelerate the commercialisation of next-generation, eco-friendly tonnage.