UK MCA: What to know when using ammonia as a fuel

The UK Maritime and Coastguard Agency (MCA) has provided an overview of the advantages, challenges, regulations, and guidance surrounding the use of ammonia as a marine fuel.

Overview

According to the “MCA customer process for alternative fuels -ammonia” publication, Anhydrous Ammonia (Ammonia – NH₃) is a light, toxic, and colourless gas. Due to the chemical composition of the fuel, NH₃ is considered a zero-carbon fuel with no carbon in its chemical molecule. It does have toxicity and flammability issues, which require special handling for storage and transport. The fuel has been used in industrial sectors and is transported in the maritime field as cargo.

For vessels above 500 GT, the Maritime and Coastguard Agency (MCA) currently regulates vessels carrying ammonia as cargo under the International Maritime Organisation’s (IMO) International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code). The MCA also works with operators and Classification Societies to regulate vessels using ammonia as a marine fuel, under the IMO’s interim guidelines published as part of the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code). These are applicable through the use of the alternative design arrangement.

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For smaller vessels using ammonia as fuel, no prescriptive regulations currently exist. These cases are considered individually, guided by experts from MCA’s Technical Operations, Regulation and Standards, and Seafarer Technical Delivery teams.

Advantages of ammonia as fuel

Ammonia is liquid at -33°C and ambient pressure, reducing storage requirements compared to other cryogenic fuels, such as Liquefied Natural Gas (LNG).
It has the potential to be carbon-neutral when produced using renewable energy. Emissions are low compared to existing marine fuels (on a life cycle basis).
It rapidly dissolves in water and biodegrades quickly.
It can be used in existing marine diesel engines with appropriate modifications, which must be approved by the relevant Classification Society or Recognised Organisation.
Existing systems, such as the Haber-Bosch process, already manufacture ammonia at scale.
Ammonia has been transported as cargo by shipping since at least the 1920s, with established best practices and industry standards.

Challenges associated with using ammonia as fuel

Toxicity: Requires enhanced safety systems, including cofferdams and inerting. The space taken by cofferdams can be a challenge for existing vessels retrofitting to use ammonia.
Corrosiveness: Requires specific storage and handling arrangements.
Lower energy density: Compared to traditional fuels, ammonia requires roughly double the fuel tank capacity, which is a challenge especially for retrofitted vessels.
Production scaling: Ammonia is currently produced for various industrial uses. Production would need to scale significantly to meet the added demand from shipping.
Cost: Ammonia is currently more expensive than traditional fuel types.

Regulations and guidance for using ammonia as fuel

The IMO has developed interim guidelines for using ammonia as fuel, which can be used by owners/operators wishing to build new vessels or convert existing vessels to run on ammonia. This guidance should be used in conjunction with the IMO’s International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels (IGF Code).

Alternative design arrangement (ADA) process

As part of the requirements, the IGF Code mandates that an Alternative Design Arrangement (ADA) be submitted to the Administration and notified to the IMO. The ADA is a risk-based design process, catered for under SOLAS, which identifies the main hazards and risks associated with the operation and mitigates them to the satisfaction of the flag administration and other stakeholders. Full guidance on the ADA process is published in MSC Circular MSC.1/Circ.1212 and should be closely followed by owners/operators prior to submission to the MCA as part of the plan approval process.

The ADA process usually requires several iterations before final sign-off. The number of iterations largely depends on the quality and thoroughness of the submission. Owners/operators are therefore encouraged to ensure submissions are of a high standard to minimize the number of iterations required to reach approval. Repeat or similar designs that have already gone through the ADA process are usually signed off in a much shorter timescale.

Development of interim guidelines

The MCA is currently working with other member states at the IMO to further develop the interim guidelines on the use of ammonia as a fuel, with the expectation of them being reviewed, finalized, and adopted into the main IGF Code in the future.

Guidance for ships below 500 GT

Ships below 500 GT or those not required to comply with the IGF Code can follow a similar process described in Marine Guidance Note 664 (MGN 664). This is also a risk-based process and closely follows the ADA process.

Crew training requirements for ammonia as fuel

Crew training requirements for alternative low-flashpoint fuels are currently covered by the IGF training requirements under the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW), which includes ammonia. The MCA is currently engaging with training providers to develop a week-long methanol course for convention-sized vessels, with initial courses expected to launch in mid-2025.

Basic training for the use of ammonia as fuel will be introduced into the UK curriculum from September 2025 as part of the new syllabus developed under the Cadet Training and Modernisation (CT&M) programme. In the longer term, through the IMO, training for alternative fuels, including ammonia, will be included in the comprehensive review of the STCW, with a timeline expected by 2030.

Final certification and survey process

Following approval of the ADA/MGN 664 and associated plans, the remainder of the process follows a conventional route through survey of the vessel, ensuring the installation is built in accordance with the approved plans, leading to final certification.