Production, distribution and storage
Around 60% of the total amount of LPG produced is recovered directly from oil and gas fields (WLPGA) in which case no actual refining is needed. The remaining 40% is formed as a by-product in crude oil processing either in distillation phase or after-treatment (cracking) processes.
A major difference between conventional fuels and LPG is the storage, as LPG is gaseous at room temperatures and atmospheric pressure. Thus, a pressurized storage tanks are needed both in the fuelling stations and in vehicles.
Compared to natural gas, distribution of LPG is simpler and fuelling stations are significantly cheaper due to the fact that LPG is liquid already at moderate pressures. For fuelling stations, LPG is usually transported by tank trucks, which have a pressure less than 25 bar. In vehicles, fixed pressure tanks with pressure levels typically in the range of 5–15 bar are used (with the safety valve set to 25 bar). Due to pressure-proof structure, LPG tanks are somewhat more expensive, heavier and require more space than gasoline or diesel tanks.
The needed pressure is, however, only around one tenth of that of needed for compressed natural gas. The volumetric energy content of LPG is lower than that of gasoline or diesel (around 70% of that of diesel). In addition, the diesel process is also more efficient than the otto cycle. Therefore, the volume of LPG tanks in vehicles has to be about twice as big as those of diesel vehicles for covering the same travel distance.

