LNG and LPG

Liquefied natural gas (LNG) and liquefied petroleum gas (LPG) are gaseous hydrocarbon fuels converted into liquids for easier storage and transport. LNG is methane-rich natural gas liquefied by extreme cooling, whereas LPG is mainly propane and butane liquefied by pressure. Their composition, handling infrastructure and principal markets therefore differ.

Origin, composition and liquefaction

• LNG is produced by purifying natural gas and cooling it to about -162°C at near-atmospheric pressure; liquefaction greatly reduces its volume for transport and storage.
• LPG is obtained mainly during crude-oil refining and natural-gas processing; it is stored as a liquid under pressure, ordinarily without cryogenic cooling.
• LNG is predominantly methane, whereas commercial LPG consists mainly of propane and butane in varying proportions.

Infrastructure and end uses

Their physical properties create different supply chains and uses.

• LNG requires insulated cryogenic tanks, specialised carriers and usually a regasification terminal before natural gas enters a pipeline network.
• LPG can be transported in pressurised cylinders, tankers or bulk vessels; it vaporises when released from storage under controlled conditions.
• LNG supplies gas grids, industries, power plants and transport applications, while LPG is widely used for cooking, heating, industry and as autogas.

Commercial and safety implications

• LNG enables pipeline-quality natural gas to be traded across seas where pipelines are unavailable or uneconomic; LPG is more readily distributed in portable cylinders and smaller consignments.
• LNG involves cryogenic hazards and boil-off management, while LPG involves pressurised storage and the risk of heavier-than-air vapour accumulating near the ground.
• Although both are flammable hydrocarbon fuels, they are not directly interchangeable because their storage systems, distribution infrastructure and appliance specifications differ.