Ammonia is regarded as a long-term relevant option because the fuel contains no carbon molecule, making a fundamentally very low tank-to-wake CO2 pathway possible.
The defining risk profile of ammonia is its toxicity. This leads to higher requirements for gas detection, ventilation, isolation concepts and emergency procedures.
With ammonia, training is not a peripheral topic but a central safety building block.
Ammonia will likely first become visible in projects that combine predictable trades, a defined set of ports and high decarbonisation ambitions.
Ammonia (NH3) has a lower heating value of approximately 18.6 MJ/kg – significantly below HFO (approximately 40 MJ/kg) or LNG (approximately 50 MJ/kg). In practice, this means a vessel requires roughly 2.5 times the tank volume compared to conventional fuel for the same range. This has substantial implications for ship design, particularly tank arrangement and cargo capacity.
The IMO has been developing Interim Guidelines for the use of ammonia as a ship fuel since MEPC 80. These build on the existing IGF Code (International Code of Safety for Ships using Gases or Other Low-flashpoint Fuels) but extend it with specific requirements for toxic fuels. The draft addresses gas detection thresholds, ventilation rates in machinery spaces, and material compatibility requirements – ammonia attacks copper, zinc and certain sealing materials.
On the engine side, MAN Energy Solutions and WinGD offer two-stroke concepts that burn ammonia in dual-fuel mode with a pilot fuel (typically VLSFO or MGO). The pilot fuel share currently sits at approximately 5–10 % of total energy input. The central engineering challenge remains ammonia’s slow flame speed and the resulting difficulties in achieving stable combustion under varying load conditions. NOx emissions are another concern: NH3 combustion can produce significant N2O (nitrous oxide) emissions – a greenhouse gas with 273 times the global warming potential of CO2 over 100 years. Exhaust gas aftertreatment via SCR catalyst is therefore considered mandatory.
Storage is either pressureless at –33 °C or under pressure at ambient temperature (approximately 10 bar at 25 °C). Type C pressure tanks are well known from the LPG cargo trade and form the basis for many current concepts. Double-walled construction with leakage monitoring in the interbarrier space is standard. Classification societies such as DNV, Lloyd’s Register and Bureau Veritas have each developed their own notations – DNV, for instance, offers the “Ammonia Fuelled” notation with additional requirements for ventilation, double barriers and emergency shutdown.
The transition to ammonia extends well beyond the engine room. Shore teams need to fundamentally revise maintenance concepts. Ammonia-resistant materials for seals, valves and piping demand new spare-part strategies. Typical costs for an ammonia fuel system on a newbuild are estimated to be approximately 15–25 % above a comparable LNG system – depending on vessel size and tank capacity.
Crew training is not a one-off event. Every officer and engineer working with the fuel system needs a solid understanding of toxicology. The occupational exposure limit (OEL) for ammonia is 20 ppm (8h-TWA); at 300 ppm there is an immediate danger to life. This means gas detection systems must be redundantly designed, regularly calibrated, and crews must know alarm thresholds, escape routes and the handling of breathing apparatus by heart.
From an OPEX perspective, green ammonia (produced using renewable electricity via electrolysis and the Haber-Bosch process) is still significantly more expensive than conventional fuel. The price range, depending on the source, is approximately 800–1,500 USD/t for green NH3, compared with roughly 400–600 USD/t for VLSFO. The economics depend heavily on how carbon pricing mechanisms – particularly the EU ETS for shipping from 2024 and FuelEU Maritime from 2025 – affect total operating costs.
From an insurance perspective, shipowners are entering uncharted territory. P&I Clubs assess ammonia projects on a case-by-case basis, and risk premiums are not yet standardised. Early and open communication with insurers during the project phase is strongly recommended.
The first commercial ammonia-fuelled vessels are expected to enter service between 2026 and 2028. Several projects are in the advanced planning stage, including concepts for bulkers and tankers on fixed routes. Scandinavian shipowners and Japanese consortia are particularly active – the latter driven by national hydrogen/ammonia strategies with government backing.
The vessel types best suited for early ammonia projects are those with long, predictable routes and sufficient space for the larger tank systems: Capesize bulkers, VLCCs and large container vessels on pendulum services. Short-sea trades and feeder services are less suitable, as the tank volume disadvantage weighs more heavily.
The realistic timeframe for broader market penetration is 2030–2035. By then, bunkering networks must be established, safety standards finalised, and sufficient operational experience gathered. The IMO’s revised GHG strategy – updated at MEPC 80 with the target of net-zero “by or around 2050” – provides the long-term framework.
Before committing to ammonia as a fuel option, systematically assess the following points:
Route profile: Do your vessels operate on fixed routes with ports that are realistically going to develop ammonia bunkering infrastructure? If your fleet trades spot, ammonia is not a viable short-term option.
Remaining service life: For vessels with fewer than 10 years of remaining service life, an ammonia retrofit is difficult to justify economically. Newbuilds with delivery from 2028 onwards are the more realistic approach.
Crew pipeline: Do you have access to crews willing and able to work with toxic fuels? Personnel availability will be a bottleneck.
Red flags: Be cautious with providers selling “ammonia-ready” as a finished concept. Check precisely what has been prepared – critical components such as the full gas detection system or the emergency shutdown logic are often missing.
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