Liquefied natural gas (LNG) is natural gas (predominantly methane, CH4) that has been converted to liquid form for ease of storage or transport. LNG is an attractive fuel choice for many vessels because it exceeds the air quality standards set forth. It takes up about 1/600th the volume of natural gas in the gaseous state. It is odorless, colorless, non-toxic and non-corrosive. Hazards include flammability after vaporization into a gaseous state, freezing and asphyxia.
The liquefaction process involves removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. The natural gas is then condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162 °C (−260 °F); maximum transport pressure is set at around 25 KPa (4 psi).
LNG Bunkering is a particular type of operation where LNG fuel is transferred from a given distribution source to a LNG fuelled ship. It involves the participation of different stakeholders, from the ship-side, LNG supplier, ports, safety personnel, administrations and policy makers. In this report, LNG bunkering only refers to LNG bunkering fuel.
|Ship Type||Truck-to-Ship (TTS)||Port-to-Ship (PTS)||Ship-to-Ship (STS)|
|Roll-on/ro-ro ship||Not suitable||Sub-optimal||Optimal|
|Coastal tanker/bulk carrier||Not suitable||Not suitable||Optimal|
|Platform Supply Vessel||Optimal||Sub-optimal||Sub-optimal|
|Smaller passenger ship||Optimal||Optimal||Sub-optimal|
|Big fishing vessel||Sub-optimal||Optimal||Optimal|
Various LNG bunkering methods are available, with truck-to-ship transfer (TTS) as the most frequently used at the moment. The choice for TTS is driven by the difficulty of developing the business case for bunkering by special barges and from the shore. However, the business case is not the only decisive criterion for selection of the preferred bunkering method. Also the operational flexibility, safety requirements and capacity will be taken into account in the future.
Ship-to-ship bunkering can take place at different locations: along the quayside, at anchor or at sea. It is the most common bunkering method used for bunkering seagoing vessels with HFO and MGO. The capacity of bunkering vessels can range from 1,000 to 10,000 m3. Because of size limitations in some ports, only smaller bunkering vessels will be able to operate in the port area.
Another bunkering method is shore-ship, whereby LNG is either bunkered directly from an (intermediary) tank or small station, or from an import or export terminal. Pipelines from the terminal to the quay are needed if the LNG terminal is not directly situated at the berth. Bunkering from pipelines has been used for LNG-fuelled ships in Norway for several years already. Under the LNG Master plan, LNG bunker terminals for inland shipping are to be built in the Port of Antwerp and in Ruse, as pilots, while a feasibility study for an LNG terminal in the Port of Constanta is scheduled.