First featured on Marine Professional (The official IMarEST magazine and newsletter)
In September 2024, the Global Centre for Maritime Decarbonisation (GCMD), in collaboration with industry, successfully conducted ship-to-ship ammonia transfers at Western Anchorage WA19, near Port of Dampier in Western Australia’s Pilbara region.
The operation was carried out in close consultation with the Australian Maritime Safety Authority (AMSA), the Department of Transportation (DoT) and the Department of Fire and Emergency Services (DFES).
This landmark trial showcased lightering and simulated bunkering operations, during which 2,700 metric tonnes of liquid ammonia were transferred between the gas carriers Green Pioneer and Navigator Global at a rate of 700-800 m³/hr. The operation took place approximately 20nm offshore within a designated 1nm anchorage zone.
The pilot aimed to trial safety protocols and operational guidelines for ammonia bunkering under realistic transfer conditions.
This effort built on GCMD’s earlier safety study for piloting ammonia bunkering in Singapore, a high-traffic, high-stakes port environment, where nearly 400 operational and locational risks were identified across various transfer configurations. Key hazards, such as ammonia leaks, toxicity, and potential fire risks, were analysed. The study concluded that these risks can be effectively mitigated to As Low As Reasonably Practicable (ALARP) levels through the implementation of robust safety measures.
The Pilbara is well-positioned to become a green ammonia hub, given its proximity to renewable ammonia production facilities, with supply expected as early as 2026. Port of Dampier also has extensive experience with ammonia export, accounting for 5% of the world’s tradable ammonia. The location is especially significant to enabling decarbonised iron ore shipping between Western Australia and North Asia.
To ensure safety, extensive pre-trial studies were conducted in four key areas: feasibility, risks, consequence and response. The findings across all four study areas confirmed that ship-to-ship ammonia transfer at anchorage can be both safe and practicable, provided that recommended safeguards and operational controls are implemented.
Safety studies’ key highlights:
Mooring and motion analysis: Historical metocean data were used to model vessel response motions at anchorage. A roll-motion threshold of four degrees was identified as a threshold for potential bridge wing collision. For safe operations, the significant wave height was limited to 0.5m, and wave periods of 9–11 seconds were flagged as this period resonates with the vessels’ natural roll periods.
HAZID and HAZOP assessments: Comprehensive hazard identification (HAZID) and hazard and operability (HAZOP) assessments were conducted across all operational phases and revealed no high-level risks. Key recommendations from these assessments that will further reduce the probability of medium-level risks included maintaining pressure-vacuum valve systems, developing post-transfer purging checklists and ensuring strict adherence to standard operating procedures.
CFD plume dispersion modelling: To assess potential impacts from accidental ammonia release, computational fluid dynamics (CFD) modelling was undertaken with a conservative release volume of 33 m³. This is four times the estimated release volume of a hose rupture scenario. Simulations considered wind speeds of 1, 5, and 10 m/s from various directions. The results indicated that Acute Exposure Guideline Level 3 (AEGL-3) concentrations of 1,600 ppm could persist for up to 60 minutes under low wind conditions but the dispersion remained within the anchorage zone. Such a release is unlikely to pose safety risks or operational disruption to vessels at adjacent anchorage points.
Ammonia-specific ERP: The emergency response plan (ERP), developed specifically for ammonia release, incorporated guidance from local authorities, including Pilbara Ports Authority, AMSA, the DoT, and the DFES. Response measures included incident tiering, PPE deployment, and coordination with onshore emergency services such as a standby firefighting tug.
The transfer was executed under a joint plan of operations, which outlined operational responsibilities, communication protocols, weather limits, and contingency measures, ensuring clarity among all participating parties.
Before the transfer, all equipment and systems were tested and verified. Emergency drills were conducted onboard both vessels to familiarise the crew with ammonia-specific response procedures, including leak management, PPE use, emergency shutdown and emergency release coupling (ERC) activation.
Commencing the trial
The operation began with vessels moored side-by-side with real-time weather monitoring throughout to ensure that operations only proceeded within the allowable sea state limits defined by the response motion and mooring analyses. Nitrogen leak testing was performed before transfer initiation to ensure system integrity.
Ammonia was then transferred in two legs—from Green Pioneer to Navigator Global, and back—using a closed-loop vapour return system to maintain safe pressure and flow. After transfer, hot gassing and nitrogen purging removed residual ammonia from the transfer lines, with ammonia concentration measurements verified before hose disconnection.
Safety protocols included the use of personal ammonia detectors for watchkeeping crew, portable gas-imaging devices for leak detection and predefined exclusion zones on deck. Response actions followed threshold concentrations that included alarms at 25 ppm for enclosed spaces and 110 ppm for secondary containment; 220 ppm to initiate shutdowns and escalation to full emergency response at 250 ppm. This aligned with the IMO draft Interim Guidelines for the Safety of Ships using Ammonia as Fuel discussed at Carriage of Cargoes and Containers (CCC) 10 and Society for Gas as a Marine Fuel ammonia bunkering guidelines that were subsequently issued.
Looking ahead
This pilot provided operational insights and real-world data that can serve as a foundation and guideline for other ports to conduct trials, ultimately strengthening port confidence in ammonia bunkering and shaping the safe and scalable adoption of ammonia as a marine fuel.
Vibin Chandrabose is director of projects at GCMD. Click to download the report here: Path to zero-carbon shipping: Insights from ammonia transfer trial in the Pilbara.
