Propane comes from beneath the Earth's crust, where it is found mixed with natural gas and oil, states the U.S. Department of Energy. In that location, it is present as a liquid as it is under such high pressure, but it becomes a gas again when returned to normal pressure.
Propane is separated from natural gas and oil as a part of the refining process in a process described by the Department of Energy. Equal amounts of propane are collected from oil and natural gas extractions. Since it is easier to store and transport as a liquid, propane is kept under high pressure and transferred to tanks in this state. Opening a valve on a propane tank allows the propane to leech into its lower-pressure surroundings, and it becomes a gas again as it emerges again from the tank.
Approximately 90 percent of the propane used in the United States comes from domestic sources, according to the Department of Energy. This propane has a wide array of uses. Some vehicles use propane rather than gasoline, and while it is less readily available than gasoline, propane is a less expensive, cleaner-burning fuel source for vehicles than gas or diesel. According to Daniels Propane, LLC, propane is routinely used to power patio haters, hut tub heaters, cooktops, clothes dryers, furnaces and water heaters.