Propane is a kissing cousin of natural gas and petroleum. Propane is usually found mixed with natural gas and petroleum deposits in rocks deep underground. Propane is called a fossil fuel because it was formed millions of years ago from the remains of tiny sea animals and plants.

When the plants and animals died, they sank to the bottom of the oceans where they were buried by layers of sand and silt. Over the years, the layers became thousands of feet thick. The layers were subjected to enormous heat and pressure, changing the energy-rich remains into petroleum and natural gas deposits. Eventually, pockets of these fossil fuels became trapped in rock layers much as a wet household sponge holds water.

Propane is just one of the many fossil fuels that are included in the liquefied petroleum (LP) gas family. Because propane is the type of LP-gas most commonly used in the United States, "propane" and "LP-gas" are often used synonymously. The chemical formula for propane is C3H8.

Just as water can change its physical state and become a liquid or a gas (steam vapor), so can propane. Under normal atmospheric pressure and temperature, propane is a gas. Under moderate pressure and/or lower temperatures, however, propane changes into a liquid. And that's the beauty of it.

Propane is easily stored as a liquid in pressurized tanks. (Think of the small tanks you see attached to a gas barbecue grill, for example.)

Propane takes up much less space in its liquid form. It is 270 times more compact in its liquid state than it is as a gas. A thousand gallon tank holding gaseous propane would provide a family enough cooking fuel for one week. A thousand gallon tank holding liquid propane would provide enough cooking fuel for almost ten years! Liquid propane instantly vaporizes into a gas when it is released from its tank to fuel propane gas appliances and equipment. Propane has been nicknamed the "portable gas" because it is easier to store and transport than natural gas.

Like its close cousin natural gas, propane is colorless and odorless. An odorant is added to propane (as it is to natural gas) to serve as a warning agent for escaping gas. And like all the fossil fuels---coal, natural gas, and petroleum--propane is a nonrenewable energy source.

History of Propane

Propane does not have a long history. It wasn't discovered until 1912 when people were trying to find a way to store gasoline. The problem with gasoline was that it evaporated when stored under normal conditions.

Dr. Walter Snelling, directing a series of experiments for the U.S. Bureau of Mines, discovered that several evaporating gases could be changed into liquids and stored at moderate pressure. The most plentiful of these gases was propane. Dr. Snelling developed a way to "bottle" the wet (liquid) gas. One year later, the commercial propane industry began heating American homes.

2. Producing and Transporting Propane

Propane comes from natural gas and petroleum wells. Fifty-five percent of the propane used in the United States is extracted from raw natural gas. (Raw natural gas is natural gas that hasn't been cleaned and processed yet.) Raw natural gas contains about 90 percent methane, five percent propane, and five percent other gases. The propane is separated from the other gases at a natural gas processing plant.

The remaining 45 percent is extracted from petroleum. Petroleum is separated into its various parts at a processing plant called a refinery.

Transporting Propane

How does propane get from natural gas processing plants or oil refineries to the consumer? Generally, propane first moves through underground pipelines to distribution terminals across the nation. Distribution terminals, which are operated by propane companies, function similarly to warehouses that store merchandise before shipping it to stores and shops. Sometimes, especially in the summer when less energy is needed for heating, propane is stored in large underground storage caverns.

After storage at distribution terminals, propane is transported via railroad tank cars, trucks, barges, and tanker ships to bulk plants. A bulk plant is where local propane dealers fill their small tank trucks.

People who use very little propane-backyard barbecue cooks, for example--must bring their propane cylinders to the dealer to be filled.

3. How Propane Is Used

Propane is used by homes, farms, business, and industry-and mostly for heating.

Homes. Propane is used mostly by homes in rural areas that do not have natural gas service. Propane appliances include ranges, ovens, space heaters, furnaces, water heaters, clothes dryers, and air conditioners. Millions of backyard cooks use gas (that's propane gas) grills for cooking. And recreational vehicles (RV's) usually have propane-fueled appliances, giving them a portable source of energy for cooking, hot water, and refrigeration.

Farms. Half of America's farms use propane to meet their energy needs, too. Farmers use propane to dry crops, brood chickens, power tractors, and warm greenhouses.

Business. Business and commercial establishments--from grocery stores to laundromats--use propane for heating and cooking.

Industry. Certain industries find propane well-suited to their special needs. Metal workers use small propane tanks to fuel their cutting torches and other equipment. Portable propane heaters give construction and road workers warmth in cold weather. Propane heaters at construction sites are used to dry concrete, plaster, and fuel pitch. Propane also heats asphalt for highway construction and repairs. And because propane is a very low-pollution fuel, fork-lift trucks powered by propane can operate safely inside factories and warehouses.

The United States uses more propane gas than any other country in the world. Propane supplies one percent of our total energy needs and ranks as the seventh most important source of energy in the country today, just after hydroelectric power and biomass.

Nearly 90 percent of the propane used in this country is produced in the United States. The other 10 percent is imported from Canada, Venezuela, and Middle Eastern countries.

4. Propane--A Transportation Fuel Too

Did you know that propane has been used as a transportation fuel for more than half a century? Taxicab companies, government agencies, and school districts often use propane, instead of gasoline, to fuel their fleets of vehicles. Today about six percent of propane's use is for transportation.

There are some interesting characteristics about propane that make it an ideal engine fuel. First, propane is clean-burning, much more so than gasoline. Propane leaves no lead, varnish, or carbon deposits that cause the premature wearing of pistons, rings, valves, and spark plugs. The engine stays clean, free of carbon and sludge. This means less maintenance and an extended engine life.

Also, propane is all fuel. It doesn't require additives usually blended into some grades of gasoline. Even without additive boosters, propane's octane rating of 110 is equal to and, in most cases, higher than available gasoline.

Propane-fueled engines produce less air pollution than gasoline engines. Carbon monoxide emissions from engines using propane are 50 percent to 92 percent lower than emissions from gasoline-fueled engines. Hydrocarbon emissions are 30 percent to 62 percent lower.

So why isn't propane used as a transportation fuel more often? For one reason, it's not as conveniently available as gasoline. Second, an automobile engine has to be adjusted to use propane fuel, and the cost of converting an engine to use propane is often prohibitive. Third, there is a slight drop in miles per gallon when propane is used to fuel vehicles.