Liquefied Natural Gas (LNG) is a fossil-derived fuel consisting primarily of methane (CH₄), stored at cryogenic temperatures (approximately −162°C) to maintain its liquid state. It is currently the most widely adopted alternative marine fuel, supported by mature engine technologies, an established global bunkering infrastructure, and existing regulatory frameworks.
Compared with conventional marine fuels, LNG offers reduced emissions of sulphur oxides, nitrogen oxides, and particulate matter, and can lower CO₂ emissions on a tank-to-wake basis. It is, however, best understood as a transition fuel, as it does not eliminate greenhouse gas emissions altogether.
As LNG is composed largely of methane, a gas with a global warming potential approximately 25 times that of CO₂, any methane slip must be carefully measured and managed when LNG is used as fuel.
Main risks
As fuel - operational
LNG Handling: As LNG is a fuel subject to continuous boil-off, it is imperative that crew are thoroughly trained in its safe handling. This encompasses both the bunkering process and onboard management of the fuel in use.
Gas Release: The principal fuel-related risk is the release of gas during bunkering or from the fuel-gas system itself, which may form a flammable vapour cloud and, in the event of ignition, lead to fire or explosion. The IGF Code is structured specifically to minimise this risk, prescribing barriers such as gas valve units, double-walled gas piping, extraction fans, nitrogen purging arrangements, and automatic fallback to fuel oil should the gas supply become unsuitable or unavailable. Where the onboard Power Management System fails to function as intended, a gas trip may result in blackout, with consequences including grounding or collision.
Cryogenic Damage: An LNG leak can cause severe cold burns to personnel and may embrittle ordinary steel or damage equipment not designed for cryogenic service.
As fuel - commercial
Compatibility gaps: Not every bunkering facility is compatible with every vessel. Mismatches across key technical interfaces can give rise to operational and commercial risks, including those relating to:
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- Quick Connect/Disconnect Couplings (QCDC),
- Emergency Shutdown (ESD) links,
- Emergency Release Couplings (ERCs),
- vapour return,
- Simultaneous Operations (SIMOPS) permits, and
- associated delay and off-hire exposure.
Contract allocation: A range of operational factors such as cooling-down, gas-freeing, maintaining heel, bunkering time, SIMOPS restrictions, and port permits can give rise to hidden charter-time costs if responsibility for them is not clearly allocated within the contract.
Fuel Price Volatility: LNG prices can fluctuate significantly, with direct consequences for voyage economics.
Limited Bunkering Infrastructure: LNG bunkering facilities remain at an early stage of development globally, which can give rise to route restrictions and scheduling challenges.
As cargo
Both LNG Handling and Gas Release, as outlined above, remain relevant when LNG is carried as cargo. In addition, the following considerations apply:
Pressure handling: As LNG cargo is continuously boiling off and generating vapour, failures in cargo compressors, vapour-handling systems, venting arrangements, forcing vaporisers, or ship/shore transfer interfaces can quickly escalate into overpressure, emergency venting, transfer stoppage, or cargo-loss events. The IGC Code is specifically designed to minimise these risks to vessel, crew, and environment.
Cargo stratification: Different LNG cargoes may vary in density and temperature. Where distinct layers form within a tank, sudden mixing or "rollover" can cause rapid vapour generation and a corresponding rise in pressure. This is of particular relevance to FSRUs and to long-term storage.
Ship-to-Ship (STS) risks: A significant proportion of LNG transfers are carried out via Ship-to-Ship operations. Cooldown, ESD testing, correct mooring, surge control, hose and arm integrity, and emergency release arrangements are all critical to safe execution. Adherence to maintenance intervals and established procedures, together with thorough crew training in these operations, is essential.
Skuld experience
Our Loss Prevention department includes a dedicated LNG team. Feel free to get in touch to learn more or discuss your specific needs.