Natural gas is a product of the decay of organic material. It is usually found in petroleum fields, but also occurs anywhere that organic material is left to decay, such as landfill sites and swamps. Another name for natural gas is marsh gas.
The primary component of natural gas is methane. Natural gas is important as a major source for electricity generation through the use of gas turbines and steam turbines. Environmentally, natural gas is a relatively clean-burning fuel, although it does produce greenhouse gases.
It is important to make the distinction that while natural gas is more clean than other fossil fuels, it is ultimately unsustainable.
The major difficulty in the use of natural gas is transport. Natural gas pipelines are the preferred means of transport, but this is impractical across oceans. Liquefied natural gas tankers have also been used, but there are some concerns about safety. In many cases, as with oil fields in Saudi Arabia, the natural gas which is recovered in the course of recovering petroleum cannot be profitably sold and it is simply burned at the oil field (known as flaring). This practice is now illegal in many countries.