Do you know the third most popular transportation fuel behind gasoline and diesel in many countries? Surprise – it’s propane, the same stuff that often powers rural homes and it is frequently used by millions of barbeques.
Worldwide, over 14 million vehicles in nearly 40 countries are now applying on autogas, the designation for propane motor fuel in most places outside the U.S. In the U.S., autogas refers to automobile gasoline that is used in piston engines powering light aircraft in place of high octane aviation gasoline or avgas. There are about 400,000 vehicles, mostly commercial, running on propane on U.S. roads.
The beneficial of using propane in an internal combustion engine includes decreased toxic and smog-forming air pollutants. There is 20 percent less nitrous oxide, 60-90 percent less carbon monoxide, 50-75-percent less unburned hydrocarbons, and fewer particulate emissions. Carbon dioxide emissions are decreased some 20 percent compared to gasoline. Unlike natural gas that is mainly methane, should propane be released into the atmosphere it is not assumed as a greenhouse gas. However, greenhouse gases, mainly CO2, are resulted when processing and combusting LPG. Propane is nontoxic and does not make environmental damage if spilled.
Between 85-90 percent of LPG used in the U.S. comes from domestic sources. Most of the remainder come from Canada. Both countries own very abundant feedstocks, with LPG either extracted from natural gas or sourced as a byproduct of crude oil processing. The weaknesses of propane include lesser availability, at least in the U.S., and a lower heating value, or energy content, than gasoline. About 5 percent less energy is supplied from LPG, which is realized into a somewhat lower miles-per-gallon (of gasoline equivalency) rating.
Engines need complicated modifications to use propane, which are different than modifications for using natural gas. Also, steel tanks must be installed to store propane. Since propane is not widely provided everywhere, bi-fuel vehicles that can either run on propane or gasoline are typical. As is the case with any bi-fuel vehicle, this increases flexibility but also greater complexity and cost, neccassery tanks for both propane and gasoline, thus reducing space for carrying people and cargo.
Typically, LPG is less expensive than gasoline or diesel, although not by a sufficient margin in the U.S. to move beyond fleet use. That’s not the case in many parts of the world, though, especially in Europe where gasoline can cost as much as $9 a gallon. Thus, a large number of automakers selling cars there to offer propane powered vehicles, most bi-fuel versions that can run on autogas or gasoline. Poland is the leader here with over two-million autogas capable vehicles. Italy is second with over a million on the road. Propane is also popular in Australia and South Korea, where Hyundai makes a hybrid LPG-electric vehicle. The Elantra LPI (Liquefied Petroleum Injection) Hybrid is the first to combine these two fuel saving technologies.
While Americans typically consider propane is only applied for commercial vehicles and forklifts (nearly a half million forklifts run on propane), more consumer and performance-oriented vehicles are offered in other markets. Here, propane can cost half as much as gasoline, thus easily paying for an Autogas-capable vehicle’s added price tag. Many are supercharged to compensate for the lower power produced when operating on autogas.
Because propane possesses a higher octane rating than today’s gasoline (MON/RON of between 90 and 110) it lends itself for use with supercharging, with the higher octane make easy the higher effective compression ratio that comes with supercharging. Consumers in other parts of the world can opt from a wide range of vehicles equipped by factory-built LPG from major brands. But this not the case in North America where automakers have not offered such vehicles since Ford discontinued its bi-fuel propane F-150 pickup in 2004. There are several noted aftermarket companies that retrofit both gasoline and diesel vehicles to run on LPG in addition to conventional fuel. In the U.S. these conversions are still mostly done on commercial vehicles like pickups, vans, and shuttle buses.
