Who isn’t familiar with CNG? Compressed Natural Gas (CNG) is an environment-friendly alternative automotive fuel. The cleaner fuel plays an important role in reducing vehicular greenhouse gas emissions and environmental pollution significantly. As its name suggests, CNG is natural gas compressed under pressure so that more of it occupies lesser volume in your fuel tank. CNG is compressed to a pressure of 200 to 250 kg/cm2. In this compressed form, it occupies less than 1 per cent of its volume at atmospheric pressure. CNG differs from Liquefied Petroleum Gas (LPG) in its constituents. CNG is gaseous, consisting of about 80 to 90 per cent methane, whereas LPG is a liquid, consisting of a compressed mixture of propane and butane in liquid form.