THE NATIONAL CLEAN BUS NETWORK
home || about ||   news  ||  the problem  ||  solutions  ||  clean bus fleets  ||  links  ||  comments

FUELS

fuels  ||  technologies  ||  regulation

LIQUID PETROLEUM GAS (PROPANE)

Liquefied petroleum gas (LPG) consists mainly of propane, propylene, butane, and butylene in various mixtures.  In the United States , the mixture is mainly propane.  It is produced as a by-product of natural gas processing and petroleum refining.  Like natural gas and unlike gasoline, LPG is a simple mixture of hydrocarbons, mainly propane/propylene (C3S) and butane/butylene (C4S).[1]  LPG is a by-product from two sources: natural gas processing and crude oil refining.  As approximately 90% of all propane used in this country comes from domestic sources, propane vehicles can help reduce U.S. dependence on imported oil and strengthen national energy security.[2]

The components of LPG are gases at normal temperatures and pressures.  When cooled or pressurized, propane becomes a liquid, which is how it is stored and generally injected.  More recently, new technologies also allow LPG to be injected as a gas.

Propane, which has been used as a transportation fuel around the world for over 60 years, powers more than 350,000 vehicles, mostly in fleets, throughout the US .  Propane powers school buses, taxi cabs, sheriff and police cars, and hundreds of fleet vehicles throughout California , where an estimated 40,000 propane-powered vehicles are currently registered.[3]

Emissions from LPG Compared to Conventional Diesel

Propane buses produce fewer emissions than those powered by diesel fuel.  Tests conducted by the U.S. Environmental Protection Agency show that propane vehicles can produce 30% to 90% less carbon monoxide than gasoline engines, 60% less ozone-forming emissions than reformulated gasoline, and about 50% fewer toxins and other smog-producing emissions.[5]  Recent tailpipe emissions tests performed on Orange County (CA) Transit Authority’s propane buses show that they emit 87% less total hydrocarbons, 50% less nitrogen oxides, and 40% less particulate matter than gasoline-fueled buses.[6] 

Propane-powered vehicles are more expensive then conventional gasoline-powered vehicles, with increases ranging from $3,000 to $5,000.[7]  The majority of propane-powered vehicles on the road today are converted vehicles.  Conversion costs generally range from $1,500 to $2,500.[8]  These price increases can be off-set through different tax credit and incentive programs.  In addition, vehicles fueled with propane often need less frequent servicing and some operators report vehicle service lives that are two to three years longer than the average gasoline vehicle.[9]  Existing service station infrastructure used for conventional fuels can be modified to dispense propane. The additional costs of adapting a station for propane use is low compared to the requirements for other alternative fuels.  There are now more than 3,400 publicly accessible propane fueling stations across the country (more than twice as many facilities offering any other type of alternative fuel).[10]