LNG bunkering is the transfer of liquefied natural gas into a ship’s fuel tanks, so the ship can burn it as fuel. This guide explains the three bunkering methods, how a transfer runs step by step, the equipment and rules involved, and the main risks. It is written for officers on LNG-fuelled ships, port staff and surveyors.
What Is LNG Bunkering?
LNG bunkering is supplying LNG fuel, stored at about -162°C, to a gas-fuelled ship from a truck, a bunker vessel or a shore terminal. It differs from oil bunkering because the fuel is cryogenic and gives off flammable vapour.
The service has spread quickly. SEA-LNG reported in January 2026 that LNG bunkering is offered in 222 ports. The bunker vessel fleet grew from one ship in 2016 to more than 62 in 2025, with 38 more on order.
Most ships that bunker LNG burn it in dual-fuel engines. The wider choice of marine fuels is covered in what fuel cargo ships use.
What Are the Methods of LNG Bunkering?
The three main methods of LNG bunkering are truck-to-ship, ship-to-ship and terminal-to-ship. Ship-to-ship is the most common for large vessels; trucks suit small volumes and ports without bunker vessels.
| Method | How it works | Typical volume or rate | Best for |
|---|---|---|---|
| Truck-to-ship (TTS) | Road tankers park on the quay and pump LNG through hoses | 40–80 m³ per truck | Ferries, tugs and small ships |
| Ship-to-ship (STS) | A bunker vessel moors alongside the receiving ship | Bunker vessels of 5,000–20,000 m³; 60–1,250 m³/h | Container ships, tankers, cruise ships |
| Terminal-to-ship (PTS) | LNG flows from shore tanks through a pipeline or loading arm | High rates from a fixed berth | Regular liner and ferry services |
| Portable tanks | Filled LNG tank containers are lifted on board and connected | Small volumes | Small vessels and remote sites |
Volumes and rates are from Gasum’s bunkering guide. ISO/TS 18683 covers shore, ship-to-ship and mobile supply in its risk assessment scope.
Ship-to-ship transfers can take place alongside, at anchor or while the receiving ship works cargo. The LNG bunkering vessels list shows the ships that do this work.
How Does an LNG Bunkering Operation Work?
An LNG bunkering operation runs through a pre-transfer checklist, connection and leak tests, a slow start, bulk transfer and topping off. Lines are then drained, purged with nitrogen and disconnected, typically after 4–12 hours.
- Pre-bunkering meeting: the supplier and receiving ship agree quantities, rates, pressures, communication and emergency procedures, and complete the bunkering checklist.
- Safety and security zones: zones are set around the transfer area, where ignition sources and unauthorised people are excluded.
- ESD test: the emergency shutdown link between supplier and ship is tested before any LNG flows.
- Connection and leak test: hoses or arms are connected, pressure-tested and purged of oxygen with nitrogen.
- Cool-down and slow start: lines are cooled gradually, and transfer starts at a low rate to check for leaks.
- Bulk transfer: the rate rises to the agreed figure, and displaced vapour returns to the supplier through a vapour return line.
- Topping off: the rate drops as tanks approach their filling limit.
- Completion: lines are drained and purged with nitrogen, couplings are disconnected, and the bunker delivery note is signed.
Simultaneous cargo or passenger operations during bunkering need a separate risk assessment and port approval.
What Equipment Is Used for LNG Bunkering?
LNG bunkering uses cryogenic hoses or loading arms, dry-disconnect couplings, emergency release couplings, an ESD link and a vapour return line. The receiving ship has a bunker station built to the IGF Code.
- Cryogenic hoses or loading arms: rated for cryogenic service and the transfer pressure.
- Dry-disconnect couplings: close on both sides when separated, so almost no LNG escapes.
- Emergency release coupling (ERC): separates automatically if the ships drift apart, sealing both ends.
- ESD link: lets either party stop pumps and close valves on both sides at once.
- Vapour return line: sends displaced boil-off gas back to the supplier, keeping tank pressure down.
- Nitrogen supply: purges lines before and after transfer.
- Drip trays and water curtain: protect the hull steel from cryogenic spills, which would make it brittle.
The receiving ship’s tank pressure is the main limit on transfer rate. The boil-off gas guide explains why warm tanks and lines produce extra vapour.
What Rules Apply to LNG Bunkering?
The IGF Code governs LNG-fuelled ships and their bunker stations, and the IGC Code governs bunker vessels. ISO 20519 and ISO/TS 18683 set procedures and risk assessment.
- IGF Code: the International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels, in force since 1 January 2017 under SOLAS.
- IGC Code: applies to LNG bunker vessels, because they carry LNG in bulk as cargo.
- ISO 20519: the specification for bunkering LNG-fuelled vessels, covering equipment, procedures and the bunkering checklist.
- ISO/TS 18683:2021: guidelines for safety and risk assessment of LNG bunkering, including safety zones and simultaneous operations.
- SGMF guidelines: industry bunkering safety guidance from the Society for Gas as a Marine Fuel.
- Port rules: each port authority approves bunkering locations, operators and simultaneous operations.
Crew on IGF ships need basic or advanced training in gas-fuelled ship operations under the STCW Code.
What Are the Risks of LNG Bunkering?
The main risks of LNG bunkering are cryogenic burns, brittle fracture of hull steel, a flammable vapour cloud and methane release. LNG is not toxic, and its vapour rises once warm, but cold vapour spreads low at first.
- Cryogenic exposure: liquid or cold vapour causes severe burns and makes ordinary steel brittle.
- Flammable vapour: methane burns in air between about 5% and 15% by volume.
- Rapid phase transition: LNG spilled onto water can vaporise violently.
- Over-pressure: warm tanks or a fast transfer raise tank pressure until relief valves lift.
- Methane release: venting during bunkering adds greenhouse emissions.
Dry-disconnect couplings, ERCs, the ESD link and strict safety zones control these risks. Following the agreed checklist matters as much as the hardware.
Is LNG a Cleaner Marine Fuel?
LNG cuts sulphur oxides and particulate matter almost to zero and lowers NOx and CO₂ compared with fuel oil. Unburned methane, called methane slip, offsets part of the climate benefit.
- SOx and particulates: natural gas contains almost no sulphur, so LNG meets ECA sulphur limits without scrubbers.
- NOx: low-pressure gas engines meet IMO Tier III limits in gas mode.
- CO₂: methane has more hydrogen per unit of carbon, so burning it releases less CO₂ than fuel oil for the same energy.
- Methane slip: since January 2026, the EU Emissions Trading System charges for methane from ships, so slip now has a direct cost.
Bio-LNG and synthetic methane use the same bunkering infrastructure. That gives LNG-fuelled ships a route to lower lifecycle emissions as part of shipping decarbonization.
LNG has lower energy per cubic metre than fuel oil. Ships therefore need larger, insulated fuel tanks, which take up cargo space.
Where Is LNG Bunkering Available?
LNG bunkering is available in 222 ports worldwide, according to SEA-LNG. Singapore and Rotterdam are the largest hubs, with ship-to-ship bunkering at anchor and in port.
- Singapore: LNG bunker sales reached 212,000 tonnes in the first half of 2024, according to the Maritime and Port Authority.
- Rotterdam: the Gate terminal’s small-scale jetty loaded 57 vessels in the first quarter of 2024, many of them bunker ships.
- Other hubs: major liner ports in Europe, Asia and the Middle East offer LNG, along with many ferry ports in Northern Europe.
Bunker availability is still thinner than for fuel oil. LNG-fuelled ships on tramp trades plan bunkering further ahead.
What Is the Difference Between an LNG Bunker Vessel and an LNG Carrier?
An LNG bunker vessel delivers LNG fuel to other ships, usually inside a port, while an LNG carrier moves cargo between terminals. Bunker vessels are much smaller and built for frequent ship-to-ship transfers.
Most bunker vessels carry 5,000–20,000 m³, against about 174,000 m³ for a standard LNG carrier. They have fenders, transfer cranes and bunkering manifolds on both sides.
What Do Inspectors Check on LNG Bunkering?
Port authorities, port State control and class surveyors check the bunker station, the ESD link, gas detection, crew training and the bunkering records. Many ports also require a pre-approved bunkering plan and operator licence.
- Port State control: the Paris MoU has PSC guidelines on the IGF Code, covering bunker stations, gas detection and certificates. See port State control MoUs.
- Class surveys: the fuel system, tanks and bunker station are surveyed under the IGF Code and class rules.
- Port authority: checks the operator licence, checklist, safety zone and simultaneous-operation approval for each transfer.
Related Topics
Frequently Asked Questions
What is LNG bunkering?
LNG bunkering is the transfer of liquefied natural gas into a ship’s fuel tanks, so the ship can burn it as fuel. It is done by truck, bunker vessel or shore terminal.
How does LNG bunkering work?
The supplier and ship agree the plan, test the emergency shutdown link and connect hoses or arms. LNG flows at a slow rate first, then at full rate, while displaced vapour returns to the supplier.
How long does LNG bunkering take?
A typical LNG bunkering operation takes 4–12 hours. The time depends on the volume, the transfer rate and how warm the receiving tanks are.
What is the difference between an LNG bunker vessel and an LNG tanker?
An LNG bunker vessel delivers fuel to other ships, usually inside a port. An LNG tanker, or carrier, moves LNG cargo between export and import terminals and is much larger.
How many ports offer LNG bunkering?
SEA-LNG reported in January 2026 that LNG bunkering is offered in 222 ports worldwide, up from 198 a year earlier.
Is LNG bunkering dangerous?
LNG is cryogenic and its vapour is flammable, so bunkering needs strict procedures and safety zones. LNG is not toxic, and dry-disconnect couplings and emergency shutdown systems limit any leak.
Which rules apply to LNG bunkering?
The IGF Code covers LNG-fuelled ships and their bunker stations, and the IGC Code covers bunker vessels. ISO 20519 and ISO/TS 18683 set bunkering procedures and risk assessment, and ports add local rules.
Can LNG-fuelled ships use bio-LNG?
Yes. Bio-LNG is chemically the same as fossil LNG, so it uses the same bunkering equipment and engines, and lowers lifecycle emissions.
- Great Lakes Maritime Academy: Programs, Cost and Admission – October 14, 2026
- Bunker Delivery Note (BDN): Contents, MARPOL Rules and Checks – October 11, 2026
- Oil Record Book: Part I and Part II Entries, Rules and PSC Checks – October 11, 2026
