CNG means compressed natural gas.
Pakistan has one of the world's largest natural gas reserve at Sui, Baluchistan which is commonly reffered as Sui gas. When this gas is compressed at high pressures up to 200 bars and stored in standard cylinders, it is called CNG. It contains up to 85 percent methane and the rest is ethane, propane, butane, etc. Its use as an alternative automobile fuel in Pakistan was recommended by us (a group of 8 Dcetians) in our engineering final year project thesis report submitted in 1994. At that time there were only a few vehicles running experimentally on CNG in Karachi and Islamabad. Since then its use as an alternative auto mobile fuel has increased by leaps and bounds due to its environment friendlyness.