Liquified Natural Gas (LNG) is mostly methane with some ethane and is typically transported in cryogenic containers as it would require too much pressure to otherwise keep it in a liquid state. Even when transported in cryogenic tanks there is some boil off that is either captured and recompressed or used as fuel for the tanker.

Liqified Petroleum Gas (LPG) is a mixture of propane and butane which does not require cryogenic storage and will remain liquid.