LNG is the acronym for liquefied natural gas, that has been made over millions of years of transformation of organic materials, such as plankton and algae. Natural gas is 95% methane, which is actually the cleanest fossil fuel. The combustion of natural gas primarily emits water vapour and small amounts of carbon dioxide (CO2). This property means that associated CO2 emissions are 30 to 50% lower than those produced by other combustible fuels.
Liquefaction as an economical transport and storage method
Natural gas is extracted from fields located predominantly in countries such as Algeria, Norway, Qatar, Russia, Nigeria and the USA. The distance between these countries and their markets means that it is not always possible to transport the natural gas produced via gas pipelines; in this case, the easiest and most economical alternative is to ship it by sea in LNG tankers.
To enable maritime transport, the natural gas is cooled down by means of a refrigerated cycle (compression, condensation, expansion, evaporation) that transforms the gas into a liquid form at -160°C: this is known as Liquefied Natural Gas (LNG). LNG, which is largely composed of methane (85 to 99%), is odourless, colourless, non-toxic and non-corrosive.
Once it has been liquefied, very large quantities of Liquefied Natural Gas can be stored and transported in LNG tanker ships. The cargo is transported in thermally insulated tanks, specially designed to maintain the natural gas in liquid form at -160°C.
Natural gas is the lightest hydrocarbon, with one carbon atom for 4 hydrogen atoms (CH4). Its combustion does not emit soot, dust or fumes. It generates 30% less carbon dioxide (CO2) than fuel oil and 45% less than coal, with a twofold reduction in nitrogen oxide (N0x) emissions and very low sulphur dioxide (SO2) emissions.