Liquefied Petroleum Gas (LPG) is a mixture of propane and butane. When used as a vehicle fuel it is often referred to as autogas. The simple chemical make up of the gases ensures that they are clean burning.
LPG has the special property of becoming liquid at atmospheric temperature if moderately compressed and reverting to gases when the pressure is sufficiently reduced. This is advantageous when transporting and storing these products in the liquid state, in which they are roughly 250 times as dense as they are when gases.
Where Does It Come From?
LPG is produced as a by-product in both the extraction and refining stages of oil production. In the past it has been considered waste and flared off. It is particularly abundant in the North Sea's 'wet' crude oil.
Consequently the UK is Europe's largest producer, producing 6.4 million tonnes in 2001. Of this over 3 million tonnes were exported. Only 50 thousand tonnes (7.75%) were used as autogas. The rest was used for domestic or agricultural heating or in chemical or refinery operations.