Natural gas

Natural or marsh gas is a product of the decay of organic material. It is usually found in petroleum fields, but also occurs anywhere that organic material is left to decay, such as landfill sites and swamps, even during digestion in animals (see flatulence).

The primary component of natural gas is methane, the shortest and lightest hydrocarbon molecule. Due to the heat and attack by the active species, the methane reacts to a methyl radical (CH₃), which reacts to formaldehyde (HCHO or H₂CO). The formaldehyde reacts to a formal radical (HCO), which then forms carbon monoxide (CO). The process is called oxidative pyrolysis:

CH₄ + O₂ CO + H₂ + H₂O

Following oxidative pyrolysis, the H₂ oxidizes, forming H₂O, replenishing the active species, and releasing heat. This occurs very quickly, usually in less than a millisecond.

H₂ + ½ O₂ H₂O

Finally, the CO oxidizes, forming CO₂ and releasing more heat. This process is generally slower than the other chemical steps, and typically requires a few to several milliseconds to occur.

CO + ½ O₂ CO₂

Natural gas is important as a major source for electricity generation through the use of gas turbines and steam turbines. Environmentally, natural gas is a relatively clean-burning fuel, although it does produce greenhouse gases. It is important to make the distinction that while natural gas is cleaner than other fossil fuels, it is ultimately unsustainable. The extraction and transporting phase adds pollution to our environment, and has been blamed for birth defects and other health effects by Wiebo Ludwig of Pincer Creek, Alberta.

The major difficulty in the use of natural gas is transport. Natural gas pipelines are the preferred means of transport, but this is impractical across oceans. Liquefied natural gas tankers have also been used, but there are some concerns about safety and economics. In many cases, as with oil fields in Saudi Arabia, the natural gas which is recovered in the course of recovering petroleum cannot be profitably sold, and is simply burned at the oil field (known as flaring). This wasteful practice is now illegal in many countries, especially since it adds greenhouse gas pollution to the atmosphere, and since a profitable method may be found in the future. The gas is instead re-injected back into the ground for possible later recovery, and to assist oil pumping by keeping underground pressures higher.

Natural gas is often stored as compressed natural gas or CNG, for use in rural homes without connections to pipedd-in public utility services, or with portable grills.

In any form, a strong bad scent is deliberately added to the otherwise colorless and odorless gas, so that leaks can be detected by the smell before an explosion occurs. In mines, sensors are used instead, replacing the previous use of the canary.