Natural Gas is a clean burning fuel increasing being used as an alternative to petroleum and diesel. Like petroleum and related products, Natural Gas is a fossil fuel consisting of a mixture of hydrocarbons, mainly methane. It is formed when layers of buried plants and animals are exposed to intense heat and pressure over thousands of years.
Reserves of Natural Gas have been found in over ninety countries around the world. Usually found in gas wells near crude oil reserves 3000 to 15,000 feet below the Earth’s surface, Natural Gas may be burnt to generate electricity or used in vehicle engines as an alternative, cleaner burning fuel.
 Why should I be aware of this?
Natural gas is one of the cleanest burning alternative fuels available. CNG-powered vehicles have lower air exhaust emissions compared to petrol or diesel-powered vehicles. Also, analyses of the emissions from CNG vehicles show that they contain significantly fewer smog-producing gases that damage the ozone layer of the atmosphere-- carbon monoxide and nitrogen oxides are ninety per cent and sixty per cent lower, which carbon dioxide, a greenhouse gas, is almost forty per cent lower compared to cars with conventional fuels.
 Natural gas and health
Natural gas is traditionally known to adversely affect both classical allergy and chemical sensitivity. It has been found that patients with complex allergies and sensitivities will have only limited success with their treatment programs, if they are living in a home that has natural gas or if they are in an area where there is natural gas transportation or leakage. Even living in a community with piped natural gas can cause serious damage.
As natural gas is lighter than air it rises up into your living and sleeping areas. Fuel oil on the other hand is heavier than air and thus sinks. Gas combustion generates copious amounts of water vapor contributing to moulds, dust mites, viruses and bacteria, providing a transport mechanism for these and other respirable particulates and volatile organic compounds deep into the lungs and thus into the body.
 Natural gas and environment
Some studies suggest that Natural gas is not as harmless as it is made out to be. Inhaling gas that has leaked from pipes may result in environmentally induced ailments, asthma and allergies.
CNG is a flammable vapor and can be a fire danger. Even though it is lighter than air, and is unlikely to settle in low level areas even if it leaks, a leaking pipe in a closed house could let it build up to explosive levels.
Environmentalists today are also questioning the viability of replacing coal and petroleum with natural gas, just because natural gas results in fewer emissions. It is, all said and done, still a non-renewable resource. Further, its extraction and the construction of natural gas power plants can destroy natural habitat of local flora and fauna. Possible land resource impacts include erosion, loss of soil productivity, and landslides.
Further, while there is no doubt that natural gas produces fewer emissions than coal or oil -- it does emit nitrogen oxides and carbon dioxide, but in lower quantities. Methane, a primary component of natural gas and a greenhouse gas, can also be emitted into the air when natural gas is not burned completely. Similarly, methane can be emitted as the result of leaks and losses during transportation.
 All about Natural Gas
Natural Gas, which is odorless, colorless, and tasteless, may be used in three forms – Compressed Natural Gas (CNG), Liquified Natural Gas (LNG) or in its natural gaseous form, Piped natural Gas. However, since Natural Gas cannot be replenished on a human time frame, it is classified as a non-renewable resource.
Its main component is methane, a relatively stable hydrocarbon. Other than methane, piped Natural Gas also contains ethane, propane, nitrogen, helium, carbon dioxide, hydrogen sulfide, and water vapor.
 Renewable alternatives to Natural Gas
The most viable alternative to natural gas is Bio Gas. Both gases have nearly identical compositions, so the same burners can be used for both fuels. Bio-gas can be produced from plant or animal waste, or a combination of both. Millions of cubic metres of methane in the form of swamp gas or bio-gas are produced every year by the decomposition of organic matter, both animal and vegetable, which makes this resource easily and quickly renewable.
 Natural Gas applications in different countries
Natural Gas was first thought of as an automotive fuel in the 1930s. Australia was one of the first countries to use it, and the first Australian vehicle rolled out with a Natural Gas-powered engine in 1937. France used CNG extensively in World War 1. Canada and New Zealand started using natural gas in the early 1970s, while the natural Gas programme in India began in 1984.
In India, Natural Gas was first used by the fertilizer and power industries. Gas Authority of India introduced a CNG network in 1992, and it became recognized as an automotive fuel in 1994 under the Central Motor Vehicle Act. Since 2002, the Delhi government converted all state-run buses to CNG, a move that has brought the metro’s pollution levels perceptibly down. Other cities like Mumbai, Vadodara, Surat and Ankleshwar are now following suit.
 The principle behind CNG engines
CNG is stored in special cylinders in the vehicle, at a high pressure (3,000 to 3,600 pounds per square inch). When the accelerator is pressed, CNG enters the engine compartment from the high pressure fuel line. From here it reaches the regulator, where pressure is reduced to normal atmospheric pressure. After this, it passes through the fuel injectors and into the combustion chambers of the vehicle. The process of combustion releases energy that the vehicle needs to move.
 Generating electricity with Natural Gas
Power plants use several methods to convert gas to electricity. One method is to burn the gas in a boiler to produce steam, which is then used by a steam turbine to generate electricity. A more common approach is to burn the gas in a combustion turbine to generate electricity.
Another electricity generation method that is growing in popularity, is to burn the natural gas in a combustion turbine and use the hot combustion turbine exhaust to make steam to drive a steam turbine. This technology is called "combined cycle" and achieves a higher efficiency by using the same fuel source twice.
CNG is more energy efficient than petrol as it is rated as 130 octane, compared to petrol’s rating of 93 octane. This allows CNG-powered engines to have greated thermal efficiency and better compression ratios and improved thermal efficiency, which in turn reduce carbon dioxide emissions.
Further, noise level of CNG engines is much lower than that of diesel engines.
- A Student's Guide to Alternative Fuel Vehicles
- Clean Alternative Fuels
- Allergy and Environmental Health Association
 Additional Information
- For a comparison of the properties of natural gas and petroleum visit CNG - Compressed Natural Gas
- For safety tips while using piped natural gas, visit 'Gas
- To learn more about appropriate emergency responses to CNG vehicle mishaps, visit EMERGENCY RESPONSE TO NATURAL GAS VEHICLES