CNG (Compressed Natural Gas) is a fuel obtained from natural gas, but when it is burned it was found that it produces very less, about 50 % less amount of hydrocarbons than when coal, petroleum etc are burned. It also produces a lower amount of greenhouse gas than the other fuels and therefore does not affect in temperature rising or global warming. So it is said that CNG is a cleaner gas in comparison to other fuels as it produces less pollution and is less harmful to the environment.