Natural gas

Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Usually low levels of trace gases like carbon dioxide, nitrogen, hydrogen sulfide, and helium are also present. Natural gas is colorless and odorless, so odorizers such as mercaptan, which smells like sulfur or rotten eggs, are commonly added to natural gas supplies for safety so that leaks can be readily detected.

Not to be confused with gasoline, biogas, or liquefied petroleum gas. Natural gas is a fossil fuel and non-renewable resource that is formed when layers of organic matter (primarily marine microorganisms) decompose under anaerobic conditions and are subjected to intense heat and pressure underground over millions of years.The energy that the decayed organisms originally obtained from the sun via photosynthesis is stored as chemical energy within the molecules of methane and other hydrocarbons. Natural gas can be burned for heating, cooking, and electricity generation. It is also used as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals and less commonly used as a fuel for vehicles. The extraction and consumption of natural gas is a major and growing contributor to climate change. Both the gas itself (specifically methane) and carbon dioxide, which is released when natural gas is burned, are greenhouse gases. When burned for heat or electricity, natural gas emits fewer toxic air pollutants, less carbon dioxide, and almost no particulate matter compared to other fossil and biomass fuels.However, gas venting and flaring, along with unintended fugitive emissions throughout the supply chain, can result in natural gas having a similar carbon footprint to other fossil fuels overall. Natural gas can be found in underground geologic formations, often alongside other fossil fuels like coal and oil (petroleum). Most natural gas has been created through either biogenic or thermogenic processes. Biogenic gas is formed when methanogenic organisms in marshes, bogs, landfills, and shallow sediments anaerobically decompose but are not subjected to high temperatures and pressures. Thermogenic gas takes a much longer period of time to form and is created when organic matter is heated and compressed deep underground. During petroleum production, natural gas is sometimes flared rather than being collected and used. 

Before natural gas can be burned as a fuel or used in manufacturing processes, it almost always has to be processed to remove impurities such as water. The byproducts of this processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons. Hydrogen sulfide (which may be converted into pure sulfur), carbon dioxide, water vapor, and sometimes helium and nitrogen must also be removed. Natural gas is sometimes informally referred to simply as "gas", especially when it is being compared to other energy sources, such as oil or coal. However, it is not to be confused with gasoline, which is often shortened in colloquial usage tousage to "gas", especially in North America.    

History 

Natural gas can come out of the ground and cause a long-burning fire. In ancient Greece, the gas flames at Mount Chimaera contributed to the legend of the fire-breathing creature Chimera. In ancient China, gas resulting from the drilling for brines was first used in about 500 BC (possibly even 1000 BC). The Chinese transported gas seeping from the ground in crude pipelines of bamboo to where it was used to boil salt water to extract the salt in the Ziliujing District of Sichuan. The discovery and identification of natural gas in the Americas happened in 1626. In 1821, William Hart successfully dug the first natural gas well at Fredonia, New York, United States, which led to the formation of the Fredonia Gas Light Company. The city of Philadelphia created the first municipally owned natural gas distribution venture in 1836.By 2009, 66,000 km3 (16,000 mi3) (or 8%) had been used out of the total 850,000 km3 (200,000 mi3) of estimated remaining recoverable reserves of natural gas. Based on an estimated 2015 world consumption rate of about 3,400 km3 (815 mi3) of gas per year, the total estimated remaining economically recoverable reserves of natural gas would last 250 years at current consumption rates. An annual increase in usage of 2–3% could result in currently recoverable reserves lasting significantly less, perhaps as few as 80 to 100 years. 

 Advantages of natural gas

 Natural gas is abundant. If consumption remained at present levels, the International Energy Agency (IEA) estimates there are enough recoverable resources to last around 230 years. It is versatile. A gas-fired power station takes much less time to start and stop than a coal-fired plant. This flexibility makes it a good partner to renewable sources of energy such as solar and wind, which are only available when the sun shines and the wind blows. 

Gas is the cleanest-burning hydrocarbon, producing around half the carbon dioxide (CO2) and just one tenth of the air pollutants of coal when burnt to generate electricity. There is enormous potential to reduce near-term CO2 emissions and air pollution by using gas instead of coal. Gas is now so widely available through LNG, that it can help countries deal with short-term supply disruptions. After the Fukushima disaster, Japan shut down its nuclear reactors and relied on LNG to make up much of its lost electricity supply. In some cases, it is cheaper to produce gas than coal. The most efficient gas-fired plant has investment costs of $1,100 per kilowatt, according to the IEA, compared with $3,700 for the most efficient coal-fired plant. Gas-fired power becomes more competitive again when long-term costs associated with climate change and the impact of air pollution, both on people and the environment, are included. Gas also has a growing number of uses, including the use of LNG as a lower-emission alternative to diesel and heavy fuel oil in transport.