Like coal and oil, natural gas is a fossil fuel. Fossil fuels (which we burn to generate heat and electricity) are non-renewable sources of energy formed in the earth over the past 550 million years, typically from the remains of marine microorganisms and plants. Sealed off from oxygen and put under ever-increasing amounts of heat and pressure, this organic matter undergoes a thermal breakdown process that ultimately converts it to hydrocarbons.
The lightest of these hydrocarbons occur in a gaseous state known collectively as “natural gas,” which in its pure form is a colorless, odorless gas composed primarily of methane.
Natural gas is a growing energy source—generating less carbon dioxide than coal when burned and cheaper than other fossil fuels. More here: climaterealityproject.org