Compressed natural gas (CNG) is a fuel gas mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 10–25 megapascals (1,450–3,600 PSI), usually in cylindrical or spherical shapes.

Advantages

1. Natural gas vehicles have lower maintenance costs than other hydrocarbon-fuel-powered vehicles.
2. CNG fuel systems are sealed, preventing fuel losses from spills or evaporation.
3. Increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil.
4. Being a gaseous fuel, CNG mixes easily and evenly in air.
5. CNG is less likely to ignite on hot surfaces, since it has a high auto-ignition temperature (540 °C), and a narrow range (5–15 percent) of flammability.
6. CNG-powered vehicles are considered to be safer than petrol-powered vehicles.
7. Due to lower carbon dioxide emissions, switching to CNG can help mitigate greenhouse gas emissions.However, natural gas leaks (both in the direct use and in the production and delivery of the fuel) represent an increase in greenhouse gas emissions. The ability of CNG to reduce greenhouse gas emissions over the entire fuel lifecycle will depend on the source of the natural gas and the fuel it is replacing.

Drawbacks

1. Compressed natural gas vehicles require a greater amount of space for fuel storage than conventional petrol-powered vehicles. Since it is a compressed gas, rather than a liquid like petrol, CNG takes up more space for each GGE (petrol gallon equivalent). 

2. Leakage of unburned methane as natural gas is a significant issue because methane, the primary component of natural gas, is a powerful, short-lived greenhouse gas. It is more than 100 times more potent at trapping energy than carbon dioxide (CO2), the principal contributor to man-made climate change.