LPG Vs CNG; which is the best?

Compressed Natural Gas (CNG)

Compressed Natural Gas (CNG) is one of the best fuel for the automobiles in comparison with the gasoline (petrol) or diesel fuel. It gives more mileage and considered to be an environmentally "clean" alternative to those fuels. CNG is made by compressing methane (CH₄) extracted from natural gas. It can be easily stored in hard containers, usually cylinders, tankers, etc.

Due to high fuel prices and environmental concerns, compressed natural gas is starting to be used in light-duty vehicles and heavy duty vehicles like auto-rickshaws, cars, buses, and school buses. But, this is not becoming widely available is because CNG takes a lot more space to store than gasoline. Even though it is a compressed gas, rather than a liquid like gasoline, it takes up more space for each GGE (Gallon of Gas Equivalent). CNG requires a much larger volume to store the same mass of natural gas and the use of very high pressures (3000 to 4000 lbf/in² , or 205 to 275 bar). This makes it difficult to design smaller vehicles that look and operate like the vehicles that people are adopted to.

CNG has grown into one of the major fuel sources used in car engines in India and most of the countries. The use of CNG is mandatory for the public transport system of India's capital New Delhi as well as for the city of Ahmedabad, Gujarat. The Delhi Transport Corporation is the world's largest fleet of CNG buses. The government of India planning to implicate the CNG operated public transport in other cities of the India.

Liquefied petroleum gas (LPG)

Liquefied petroleum gas (LPG) is made by a mixing of hydrocarbon gases. It is used as a fuel in heating appliances, vehicles, as well as home appliances. LPG is increasingly replacing chlorofluoro-carbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer.

LPG is mixes in the proportion of both propane (60%) and butane (40%), depends upon the season, in winter there is more percentage of propane and in the summer more percentage of butane. It also contains Propylene and butylenes in small concentration. A powerful odorant, ethanethiol, is added so that leaks can be detected easily. The international standard is EN 589.

LPG is manufactured during the refining of crude oil, or extracted from oil or gas streams as they emerge from the ground. LPG is evaporated at the room temperatures and pressures. Due to this it is stored and distributed in the pressurized cylinders or bottles. These continers are not filled completely; they are approximately filled to between 80 to 85% of their capacity. The ratio between the volumes of the vaporised gas and the liquefied gas varies depending on composition, pressure and temperature, but is typically around 250:1

LPG results in a considerable loss of power and torque vis-à-vis petrol (about 5-8 per cent on an average), and this means that stressed the engine a lot more on a daily basis. And that means that engine life will drop by a bit.

Cars; already exist

Some automobile company has installed the CNG/ LPG kit in their cars such as Ford has Ikon Flair CNG, Mitsubishi offers CNG kit in Lancer sedan. Maruti offers Omni LPG and WagonR, Hyundai will launch a CNG variant of santro soon. General Motors has CNG version of its Chevrolet Opera in 2006. Tata Motors offers authorized CNG kit fitment at their dealerships for the Indica and Indigo Marina, etc.

LPG is usually chosen over CNG as the fuel of choice, because it is easily available nationwide as compared to CNG. LPG is available in more than 40 cities and CNG is just available in the metropolitan cities. It can be stored at a much lower pressure than CNG, at approximately 5 to 7 bar, and as a result, the tank does not have to be built super-tough and it requires less space. The other positive aspect about LPG is that it does not inhibit engine performance as much as CNG does. Thus for a personal vehicle, it makes sense to go for LPG while for commercial vehicles CNG vehicles will.

The amount requires to installation for the LPG/ CNG kit is approximately Rs 15000 – Rs 40000.