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Understanding CNG

Compressed Natural Gas (CNG) is composed primarily of methane, a hydrocarbon gas. Natural gas exists naturally under the earth’s surface and is drilled in the same manner as crude oil is drilled from the earth. It is estimated that the natural gas reserves of the earth are around 135,000 billion cubic meters. Since the 1990s the number of gas reserves being discovered has been growing at a rate of 5% per year. Because of the increasingly common trend of moving away from polluting and expensive crude oil and petroleum based fuels, the use of compressed natural gas as a fuel is growing.

It has been several decades since CNG has been used in vehicles as an alternative to gasoline or petrol. According to some estimates, the number of vehicles currently running all over the world on CNG is close to five million. The countries that are the leading consumers of CNG in the world are Brazil, Argentina and Pakistan. It shows that the largest consumers of CNG are located in South America and Asia while Europe and North America are lagging behind.

CNG is a much better fuel as compared with LPG or gasoline. Firstly, it is a much safer fuel. Being composed of methane, natural gas is lighter than air, and as a result in the case of any leakage it rises into the atmosphere and diffuses quite rapidly, so there is little risk of combustion. On the other hand, gasoline or petrol is a liquid and in case of leakage it collects on the ground where it can catch fire quite easily. CNG is also better on this count. CNG has a narrower range of combustion so it is not as likely to catch fire quickly as gasoline or LPG. Both these factors make CNG a much better alternative. In addition, CNG is also much better for the car because it does not reduce the efficiency of the engine over time, which is something that happens with the use of gasoline as it does not lead to the wear and tear of the engine and crankcase components.

However, the most important benefit of CNG is its environmental advantage. CNG does not contain any traces of sulfur and lead, both of which are major components of greenhouse gases and also cause acid rain. CNG also produces one tenth of the carbon monoxide as gasoline or petrol.

Compressed natural gas is stored under high pressure in gas cylinders. Special care has to be taken to control the pressure of these cylinders because if the pressure gets out of control then the cylinder could burst causing injury and serious damage to the surrounding area. For this purpose CNG cylinders installed in cars are provided with a burnt disc. This provides an additional cover to the cylinder so that if the pressure inside the cylinder becomes excessive the burnt disc ruptured and the overall pressure of the cylinder is maintained. The cylinders are installed along with other components making up a CNG conversion kit in cars that have petrol or gasoline powered system.