LNG is natural gas in its purified and liquefied form. It is condensed into a liquid by cooling it to approximately -162 °C at close to atmospheric pressure.

The colourless, odourless, non-toxic and non-corrosive liquid consists mainly of methane (CH4) with low concentrations of other hydrocarbons (e.g. ethane, propane and butane) and inert components such as nitrogen.

The major advantage of LNG is its relatively high energy density: it takes up only 1/600th the volume of its gaseous counterpart and is therefore ideally suited for storage and transport.

When used as marine fuel, LNG produces no visible smoke and causes no sludge deposits. This is a significant advantage over scrubbers, which are used to reduce the SOX emissions of ships powered by heavy fuel oil. Moreover, LNG also reduces the noise level on board.