Natural gas is a mixture of gaseous hydrocarbons, viz. methane 85%, ethane, propane, butane, etc.
Methane is also known as the Marsh Gas.
Compressed Natural Gas (CNG) consists mainly of methane (95%) which is a relatively unreactive hydrocarbon and makes its nearly complete combustion possible.
It is a greenhouse gas.
The other greenhouse gases in the earth’s atmosphere are water vapour, carbon dioxide, nitrous oxide and ozone.