Liquefied petroleum gas (LPG), like oil and natural gas, is a fossil fuel. LPG is a mixture of various low-boiling-point gases produced during petroleum refining and has no fixed composition. Its main components are butene, propylene, butane, and propane. Although most energy companies do not specifically produce LPG, it is produced in small quantities as a byproduct of refining other fuels.
Refineries produce LPG during the production of other commonly used fuels.
Of the natural gas extracted from the ground by energy companies, 90% is methane. The remainder is various types of LPG, with yields varying, generally between 1% and 3%. LPG can also be separated from crude oil. Refining processes typically yield about 3% LPG, but this can be increased to 30%-40% by optimizing refinery equipment for centralized LPG extraction. The density of LPG is expressed in kg/m³, and it varies with temperature and pressure. Therefore, when expressing the density of liquefied petroleum gas, temperature and pressure conditions must be specified.