Compressed Natural Gas (CNG)
CNG (Compressed Natural Gas) is a mixture of hydrocarbons consisting of approximately 80 to 90 percent methane in gaseous form. Because of its low energy density, it is compressed to pressure of 200 to 250 Kg/cm2 (to enhance the vehicle on-board storage in a cylinder), hence the name Compressed Natural Gas. Colourless, non-carcinogenic and non-toxic, CNG is inflammable and lighter than air. It is not a liquid fuel, and is not the same as LPG (Liquified Petroleum Gas), which consists of propane and butane in liquid form.
Superior to petrol, it operates at one-third the cost of conventional fuel and is hence, increasingly becoming popular with automobile owners. Commonly referred to as the green fuel because of its lead free characteristic, it reduces harmful emissions and is non-corrosive, thus enhancing the life of spark plugs. Another practical advantage observed in countries where CNG is in already in vogue is the extension of life of lubricating oils as the fuel does not contaminate and dilute the crankcase oil. In the next millennium, alternative fuels like Compressed Natural Gas (CNG) and Liquified Petroleum Gas (LPG) would be increasingly used in automobiles.
Mumbai already has over 10,500 CNG cars/taxis and in Delhi, all public transport run on CNG.
Car manufacturers have been conducting tests on their vehicles, using LPG/CNG - both in dedicated and bi-fuel modes. While these fuels will not totally replace petrol and diesel, they may be targeted for use in particular segments, like commercial and public transport vehicles. Diesel was for a long time considered eco-friendly because it is more fuel-efficient than petrol i.e. 15-20 percent more mileage than one litre of petrol. But the 1990s have seen diesel being increasingly acknowledged as extremely detrimental to health and environment. Experiments have revealed that besides a very tiny - one micron or less, which are injurious to health. Recognizing the gravity of the situation, authorities are intensifying the thrust on use of alternate fuels like CNG and LPG which besides being less hazardous are cost-effective.