Natural gas is commonly found in the fossil state, along with oil, coal or alone in natural deposits only. It is, however, also produced by the processes of decomposition, in swamps (in this case it is also called swamp gas), in landfills, during digestion in animals and other natural processes. It is finally released into the atmosphere by volcanic activity also.

The main difficulty in the use of natural gas transportation. Pipelines are cheap, but do not allow the crossing of oceans and often, when it comes to international pipelines, pass in territories of other states, which could interrupt the flow for political reasons or otherwise. They are also used ships to transport liquefied natural gas, defined LNG, but have higher costs and safety issues. In many cases, such as in oil wells in Saudi Arabia, the natural gas that is recovered during the extraction of oil, it can not be sold profitably, is burned on the spot. This wasteful practice is illegal in many states, because releases greenhouse gases in Earth’s atmosphere unnecessarily. Instead of being burned, the gas, is increasingly being re-injected into the oil reservoir to maintain the pressure, and then allow the extraction of all the oil contained in it. The natural gas is compressed to be stored.

Having regard to the increasingly high cost of oil, it has become convenient to the process of transformation of natural gas into liquid fuels, mainly naphtha and gas oil. This process is called GTL (Gas To Liquids) and is based on a technology called Fischer-Tropsch process used by the Germans during the second world war. The Germans, by failing to provide oil fields to fuel their war machine were using coal, which, after being gasified, was converted into liquid fuel. The Fischer-Tropsch process uses a catalyst based on cobalt or iron to produce condensates and wax from natural gas suitably treated.

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