Liquefied Petroleum Gas
Mst people call liquefied petroleum gas (LPG) “propane.” That is because LPG is mostly made up of propane. Actually, LPG is made of a mixture of propane and other similar types of hydrocarbon gases. Different batches of LPG have slightly different amounts of the different kinds of hydrocarbon molecules.
These hydrocarbons are gases at room temperature, but turn to liquid when they are compressed. LPG is stored in special tanks that keep it under pressure, so it stays a liquid. The pressure of these tanks is usually about 200 pounds per square inch (abbreviated “psi”).
Propane has been used in vehicles since the 1920s. Today there are more than 200,000 propane vehicles in the United States and about 9 million worldwide. These include cars, pickup trucks, and vans; and medium- heavy-duty vehicles such as shuttles, trolleys, delivery trucks, and school buses; and off-road vehicles such as forklifts and loaders.
Propane vehicles can be equipped with dedicated fueling systems designed to use only propane, or bi-fuel fueling systems that enable fueling with either propane or gasoline.
Most LPG produced in the U.S. comes from natural gas wellhead processing. That is because natural gas has LPG gases and water vapor in it, which must be removed before the natural gas can be sent away in pipelines. Most of the LPG produced in California comes from petroleum refining.
The LPG used in vehicles is the same as that used in gas barbecues and camper appliances. LPG is also used in many homes in the country, where there are no natural gas pipelines. These homes use LPG for heating, cooking, hot water and other energy needs.
LPG fueled engines can pollute less than gasoline and diesel engines. LPG usually costs less than gasoline for the same amount of energy. In some countries LPG is used much more for vehicle fuel. In the Netherlands over 10 percent of the motor fuel used is LPG.
Propane vehicles can produce 60% fewer ozone-forming emissions (CO and NOx) than vehicles powered by reformulated gasoline. In addition, tests on light-duty, bi-fuel vehicles have demonstrated a 98% reduction in the emissions of toxics, including benzene, 1,3-butadiene, formaldehyde, and acetaldehyde, when the vehicles were running on propane rather than gasoline.
The cost of a gasoline-gallon equivalent of LPG is generally less than that of gasoline, but varies depending on location.
