Ship-to-ship ammonia bunkering operations in Singapore’s port waters can be carried out safely and effectively if robust safeguards, conservative operating limits and coordinated risk management measures are applied, according to a new report from the Global Centre for Maritime Decarbonisation (GCMD).

The study, representing Phase 2 of GCMD’s ammonia bunkering work in Singapore, provides a vessel-, location- and operation-specific safety assessment for ship-to-ship transfers using existing ammonia carriers. The analysis is intended to support interim bunkering arrangements ahead of the introduction of purpose-built ammonia bunker vessels.

Building on earlier foundational work, the report evaluates ammonia transfer operations in a high-traffic port setting and concludes that transit and side-by-side mooring of two ammonia carriers can be managed within local weather and sea-state limits. The assessment assumes conservative operating criteria and continuous pilotage throughout the operation.

Hazard identification (HAZID)and hazard and operability (HAZOP) studies identified medium-level risks, mainly linked to vessel interface, mooring arrangements, equipment and operational procedures. GCMD said these risks were assessed as tolerable provided that appropriate safeguards, checklists and emergency response planning are in place.

Quantitative risk assessment showed that defined safety zones can be established around ship-to-ship transfer operations. Deterministic modelling recommended a conservative safety zone radius of 547 metres for transfer operations conducted once a year.

Computational fluid dynamics modelling of worst-case ammonia release scenarios indicated the potential formation of toxic vapour clouds that could affect escape routes and accommodation air intakes. The findings highlight the importance of early leak detection, rapid isolation systems and effective crew protection measures.

GCMD said the results have already informed emerging industry guidance, including the Society for Gas as a Marine Fuel’s ammonia bunkering guidelines, and are intended to help prepare ports and operators for the adoption of ammonia as a marine fuel.

The full report is available through GCMD’s website.