Propane is separated from crude oil during the refining process and extracted from natural gas at a gas processing plant. It is considered a fossil fuel because it was formed from the remains of sea animals and plants. When living organisms die and sink to the bottom of the sea, sand and silt cover them, subjecting the remains to high pressure and heat, which change the chemical makeup.
Propane is made of three carbon atoms and eight hydrogen atoms. Under normal atmospheric pressure and temperature, propane is a gas, although lower temperatures and moderate pressure convert it to liquid. If stored in its gaseous form, a thousand-gallon tank is about enough fuel for a family to cook for one week. The same tank storing liquid propane instead of gas can hold 270 times the amount of fuel. Propane is odorless, so mercaptan is added as an odorant to serve as a warning if propane gas is escaping.
Although propane has historically been considered a non-renewable resource, Think Progress published an article in September 2014 about British and Finish scientists producing small amounts of propane from Escherichia coli, a naturally-occuring bacteria mostly associated with food poisoning. The propane is created from a genetically-engineered version of the bacterium and may be ready for commercial production within 10 years.