A gas widely distributed in nature, methane is a colourless, odorless gas. At normal room temperature the gas’s density is less than that of normal air. Its melting point is at –183°C and its boiling point is –164°C. It is a highly combustible gas and mixtures of anywhere between 5 to 25 percent are extremely explosive in nature. As a gas it is not toxic or fatal to the human respiratory system but can cause suffocation due to the reduction in the concentration of oxygen that it brings about. The gas is major component of natural gas. Though the gases molecular formula is CH4, within the atmosphere the gas consists of 75% CH4, 15% ethane (C2H6), and 5% other hydrocarbons, such as propane (C3H8) and butane (C4H10).
Methane is a very important energy source when it comes the generation of electricity. The gas is burned as a fuel in a gas turbine or steam boiler to generate electricity. In many cities methane is used for the purpose of domestic heating or cooking. Methane in the form of compressed natural gas is also used as an environmentally friendly fuel option for motor vehicles
Methane is used in many industrial chemical processes and generally stored in the form of liquefied natural gas (LNG). In the chemical industry methane is the main feedstock from which one derives and produces hydrogen, methanol, acetic acid and acetic anhydride. When used in the production of the above chemicals, it is converted in to a synthesis gas in a mixture of carbon monoxide and hydrogen with the help of steam reforming. Another methane derived chemical that has industrial relevance is acetylene.
Natural Gas Fields
An important extraction source of methane is geological deposits such as natural gas fields. Such fields are associated with hydrocarbon fuels often accompanied by helium and nitrogen. Closer to the earth’s surface the gas is formed by decay of organic matter as well as reworked methane from deep under the Earth’s surface i.e. sediments that are buried deeper underground and existing at higher temperatures than those which produce oil. Methane is also produced in large quantities from decaying organic wastes within solid landfills.
Methane can also be obtained through the production of bio-gas i.e. the fermentation of organic matter such as manure, sludge, human waste products and other biodegradable matter. Methane is also extracted from coal deposits. Industrially methane is produced from common atmospheric gases and hydrogen through electrolysis or other chemical processes such as the Sabatier process or Fischer-Tropsch process.
Methane in the Earth’s Atmosphere
Methane acts as an important greenhouse gas within the earth’s atmosphere. The gas has a global warming potential of about 25 over a 100years. This means that a single ton of methane will have 25 times the impact on temperature of a 1 ton carbon dioxide emission within the time frame of 100 years. About 3.5 billions years ago there a thousand times more methane in the earth’s atmosphere than there is now. The earliest methane was introduced in to the atmosphere through volcanic activity.
- Methane is a very powerful greenhouse gas because it can retain 21 times more heat than CO2.
- There's 400 gigatons of methane locked in the frozen arctic tundra
- Even if emissions of greenhouse gases were to stop immediately, earlier emissions would continue to affect climate for centuries to come.
- The Earth is heating more rapidly than it has at any other time during the past 10,000 years.
- Methane gas is abundantly trapped as a half frozen slush in the northern hemisphere's tundra permafrost regions and at the bottom of the sea.
- In what might have been an early warning, in 1986, Lake Nyos in Cameroon "burped" an amount of gases killing 1800 people.
- There are enormous quantities of naturally occurring greenhouse gasses trapped in ice-like structures in the cold northern muds and at the bottom of the seas. These ices, called clathrates, contain 3,000 times as much methane as is in the atmosphere.
- A temperature increase of merely a few degrees would cause these gases to volatilize and "burp" into the atmosphere, which would further raise temperatures, which would release yet more methane, heating the Earth and seas further.
- Environment Words- A Dictionary in Plain English, published By Images Asia
- US Environment Protection Agency's Information on Methane