Classification society DNV on Monday (28 April) released an article summarizing how shipowners can apply a practical, structured approach to gaining approval for ammonia- or hydrogen-fuelled ships. 

From engaging early with flag administrations to addressing design risks, training crews, and managing bunkering safely, DNV described seven essential steps to receive approval:

The paper – Safe introduction of alternative fuels: Focus on ammonia and hydrogen as ship fuels – offers a structured pathway for shipowners to achieve approval through IMO’s alternative design approval (ADA) process.

Seven steps to obtain approval for ammonia- and hydrogen-fuelled ships

“We outline seven steps to assist shipowners and other stakeholders in obtaining approval and safely deploying ammonia- and hydrogen-fuelled ships in today’s immature regulatory environment,” says Linda Hammer, Principal Consultant, Environment Advisory at DNV and lead author of the white paper. “The regulatory path is certainly complex, but the steps and safety measures in the paper add up to a clear, achievable pathway to ship approval and safe operations. It also explains how DNV’s support can significantly ease this process through its tailored rule sets and learnings from pilot projects.”

Understanding ADA phases: From initial design to final approval

IMO’s IGF Code (International Code of Safety for Ship Using Gases or Other Low-flashpoint Fuels) currently covers natural gas but not ammonia or hydrogen. Without detailed regulations, IMO’s risk-based ADA process (MSC.1/Circ.1455) is used. It involves demonstrating that the ship’s safety level is equivalent to that of conventional oil-fuelled vessels.

ADA has two main phases. A preliminary design approval requires a hazard identification (HAZID) study, developing a preliminary risk assessment, and defining preliminary risk-control measures and safety strategies.

Phase two, final design approval, starts with refining the design with detailed technical and safety documentation, then making a final risk assessment, addressing integration and operation-specific concerns. Then come complete system integration testing and submitting findings to the flag administration.

Role of class and flag administrations in approval process

As the IMO regulatory framework progresses towards eventually amending the IGF Code, classification societies like DNV can give shipowners a head start in designing vessels by issuing class certificates and providing prescriptive rule frameworks to support ADA. 

Flag administrations enforce statutory regulations and have the final say on approvals. Early and active engagement with the relevant flag administration is therefore the key to clarifying approval expectations and streamlining ADA.

Subject to flag administration acceptance, the DNV rules can be applied as the flag administration’s approval basis or to significantly reduce the complexity of ADA.

Simplifying ship approval: DNV’s rules for ammonia and hydrogen fuels

DNV’s classification rules for ammonia and hydrogen (i.e. the “Gas fuelled ammonia” notation published in 2021 and the 2024 “Gas fuelled hydrogen” notation) provide structured, prescriptive requirements as far as possible to simplify ADA. Applying them helps reduce uncertainty in flag administration approval, streamlines design focus by aligning with expected risk assessments, and provides predictability to shipowners, ship designers and shipyards.  

The paper describes step-by-step actions for obtaining approval. First, engage DNV and the flag administration early to clarify the approval basis. “DNV can help owners and yards in the initial contact with the flag administration to obtain necessary clarification regarding the approval scope and process,” says Hammer.

Second, align the design with DNV rules to ensure it provides a strong technical basis for risk evaluation. Third, tap into DNV’s extensive and growing experience from prior projects to anticipate what risk studies and documentation may be needed.

The paper also discusses measures to manage the new technical, human and organizational risks that both fuels bring compared to conventional fuels. DNV’s dedicated ship rules for each fuel type outline technical requirements and mitigation systems to integrate during design and operation.

Note: DNV’s full article on ‘Practical guide for approval of ammonia- or hydrogen-fuelled ships’ can be read here.

Related: DNV releases white paper on safe and scalable adoption of ammonia, hydrogen bunker fuels

Photo credit: DNV
Published: 30 April, 2025