In a recent Maritime Impact article, classification society DNV offered a concise summary of key developments in ammonia as a marine fuel, highlighting the opportunities and challenges ahead: 

Ammonia is gaining traction as a marine fuel, backed by regulatory progress, engine innovation and early fleet adoption. Due to high costs and infrastructure gaps, shipowners are advised to plan strategically when choosing the right future fuel. How far and fast ammonia as an alternative fuel can propel shipping decarbonization is examined in the DNV paper Ammonia in Shipping.

“The around 40 ammonia-capable ships on order put ammonia firmly in the decarbonization race,” says Linda Sigrid Hammer, Principal Consultant, Environment Advisory at DNV and lead author of the paper. 

“Across most barriers significant advancements have been made in the last five years, while challenges remain.” DNV’s paper analyses what it will take to get ammonia-fuelled ships approved, how to speed up the process, and practical steps for shipowners.

The paper identifies and discusses the remaining hurdles and presents them in a dashboard showing change in the status quo for ammonia fuel in 2025 compared with 2020.

Ammonia fuel rules progress

Ammonia’s toxicity requires stricter safeguards than conventional fuels. In 2020, approvals relied on risk-based case studies.

Since then, a combination of new DNV rules introduced in 2021 and updated annually and IMO interim guidelines launched in 2024 have given designers a regulatory framework to work with until binding Code amendments enter into force.

Amendments to the IGC Code (International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk) allow ammonia carriers to use cargo as fuel, with draft interim guidelines recently finalized. Binding amendments to the IGF Code (International Code of Safety for Ship Using Gases or Other Low-flashpoint Fuels) are unlikely before 2032, however.

Ammonia propulsion gains ground

Five years ago, ammonia propulsion was conceptual. By August 2025, 39 ammonia- capable ships, mainly ammonia carriers and bulkers, were on order. By late 2025 or early 2026 we will also see the first deliveries of new vessels capable to burn ammonia.

Engine developers are committed. Everllence, WinGD and J-Eng are delivering dual-fuel two-stroke engines from 2025/2026, while Hyundai’s HiMSEN H22CDF-LA four-stroke has multi-class approval. Demonstrations, including Fortescue’s Green Pioneer and ammonia-fuelled tugs in Japan and China, prove operational feasibility.

Fuel-system solutions are also emerging, such as Wärtsilä’s integrated package and Alfa Laval’s FCM Ammonia. The sector has moved from theory to deployment.

How to manage ammonia’s energy density issues

Ammonia requires nearly triple the volume of marine gas oil for the same energy, reducing range and cargo space. But design strategies, dual-fuel capability and shorter bunkering intervals make the challenge manageable.

Naval architects now weigh trade-offs between capacity, range and bunkering.

“The severity of this barrier depends heavily on ship type and trading pattern,” says Hammer. “For liner services and vessels with deck space, solutions are easier. The space issue is now seen as a manageable design problem rather than a showstopper.”

High costs and fuel gaps slow ammonia adoption

Ammonia-fuelled newbuilds still typically cost 15–20% more than conventional designs, and for some retrofits even more. Although high, the additional cost remains within feasible limits, assuming other market conditions provide sufficient incentives.

Ammonia in Shipping reports studies suggest a 16% premium for a large containership, +19% for an Aframax tanker, and +15% for midsize gas carriers, while retrofitting older bulkers can be prohibitively costly at up to 60% of remaining ship value.

“Uncertainty on cost has narrowed as designs mature, but shipyards often add risk premiums for bespoke projects. Costs should fall as production scales and designs standardize, but the capital expenditure barrier is roughly as high as in 2020,” observes Hammer. “Even if ships are ready, the toughest challenges hinge on the cost barrier, in particular the fuel cost, which remains too high.”

Note: The full article by DNV can be found here. 

Related: DNV report: Ammonia shows notable progress as bunker fuel but barriers remain

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Published: 7 October, 2025