Natural gas is a fossil fuel source of energy, which represents more than one fifth of total energy consumption in the world. It has been the fastest growing fossil fuel since the seventies.

Due to economical and ecological advantages that it presents as well as its safety qualities (e.g. reduced flammable range), natural gas is an increasingly attractive source of energy in many countries. At present, natural gas is the second energy source after oil. According to Energy Information Administration, natural gas accounted for 23% of world energy production in 1999. It has excellent perspectives for future demand. Natural gas is considered the fossil fuel of this century, as petroleum was last century and coal two centuries ago.

Total primary energy supply by fuel

Source: World Energy Outlook 2000, International Energy Agency

Natural gas presents a competitive advantage over other energy sources. It is seen as economically more efficient because only about ten per cent of the natural gas produced is wasted before it gets to final consumption. In addition, technological advances are constantly improving efficiencies in extraction, transportation and storage techniques as well as in equipment that uses natural gas.

Natural gas is considered as an environmentally friendly clean fuel, offering important environmental benefits when compared to other fossil fuels. The superior environmental qualities over coal or oil are that emissions of sulphur dioxide are negligible or that the level of nitrous oxide and carbon dioxide emissions is lower. This helps to reduce problems of acid rain, ozone layer or greenhouse gases.

Natural gas is also a very safe source of energy when transported, stored and used.

Although resources of natural gas are finite and natural gas is a non-renewable source of energy, these resources are plentiful all over the world. Natural gas reserves are continuously increasing as new exploration and extraction techniques allow for wider and deeper drilling.

The growing importance of natural gas as a major energy source is shown by the amount of investment devoted to the natural gas industry. The sector shows a great dynamism at the beginning of the new millennium. Increasing demand and prices in the recent past have led to new expansion and exploration projects in the natural gas industry. New pipeline construction projects are developed and planned all over the world. Furthermore, most governments are progressively including natural gas in their energy policy agenda, by following liberalization policies (particularly after the energy shortages of 1970s), in order to open the markets to competition. More and more, energy final users are also showing a preference for using natural gas as a clean, safe, reliable and economical source of energy. Natural gas is used for heating, cooling and several other industry uses, while it is increasingly becoming the favoured fuel for power generation.

Description/Technical Characteristics

Natural gas is colourless, odourless, tasteless, shapeless and lighter than air. It is gaseous at any temperature over -161º C. When it is at its natural state, it is not possible to see or smell natural gas. For safety reasons, a chemical odorant that smells a little like rotten eggs, Mercaptan, is added to natural gas so that it can be smelled if there is a gas leak.

Natural gas is a mixture of light hydrocarbons including methane, ethane, propane, butanes and pentanes. Other compounds found in natural gas include CO2, helium, hydrogen sulphide and nitrogen. The composition of natural gas is never constant, however, the primary component of natural gas is methane (typically, at least 90%), which has a simple hydrocarbon structure composed of one carbon atom and four hydrogen atoms (CH4). Methane is highly flammable, burns easily and almost completely, while it emits very little air pollution. Natural gas is neither corrosive nor toxic, its ignition temperature is high, and it has a narrow flammability range, making it an inherently safe fossil fuel compared to other fuel sources. In addition, because of its specific gravity of 0.60, lower than that of air (1.00), natural gas rises if escaping, thus dissipating from the site of any leak.

The carbon and hydrogen in natural gas are thought to have originated from the remains of plants and animals that were accumulated at the bottom of lakes and oceans over millions of years. After having been buried under huge layers of other sediments, the organic material is transformed into crude oil and natural gas as a result of the high pressure from the layers of sediments and the heat from the earth's core. The oil and gas are then squeezed out of the marine shales in which they were deposited, and from there go into porous sedimentary rocks. Oil and gas migrates upward through the porous rock, as it is less dense than the water, which fills the pores. Several different types of oil and gas "traps" exist.

Natural gas is found throughout the world in reservoirs deep beneath the surface of the earth and floor of the oceans. It forms as pockets of gas over crude oil deposits or is trapped in porous rock formations. Natural gas can be found in oil deposits, as associated natural gas, although non-associated natural gas is often found without the presence of oil.

When natural gas is cooled to a temperature of approximately -260°F at atmospheric pressure, it condenses to a liquid called liquefied natural gas (LNG). One volume of this liquid takes up about 1/600th the volume of natural gas. LNG weighs less than one-half that of water, actually about 45% as much. LNG is odourless, colourless, non-corrosive, and non-toxic. When vaporized it burns only in concentrations of 5% to 15% when mixed with air. Neither LNG, nor its vapour, can explode in an unconfined environment. Since LNG takes less volume and weight, natural gas is liquefied for ease of storing and transporting.

Natural gas is considered as a clean fuel because of its environmentally friendly properties: commercialised natural gas is practically sulphur free and thus it produces virtually no sulphur dioxide (SO2), natural gas emits lower levels of nitrogen oxides (NOx) emissions than oil or coal and emissions of carbon dioxide (CO2) are less than those of other fossil fuels (According to Eurogas 40-50% less than coal and 25-30% less than oil).

* For more detailed properties of natural gas and comparisons with other fuels, see Alternative Fuels Data Centre , Gas Energia or http://www.naturalgas.org

Origin and history

The discovery of natural gas dates from ancient times in the Middle East. Thousands of years ago, it was noticed that natural gas seeps ignited when lightning and created "burning springs". In Persia, Greece or India, people built temples around these "eternal flames" for their religious practices. However they did not recognize the energy value of natural gas. It was done in China around 900 BC. The Chinese drilled the first known natural gas well in 211 BC.

In Europe, natural gas was unknown until it was discovered in Great Britain in 1659 although it was not commercialised until about 1790. In 1821 in Fredonia, United States, residents observed gas bubbles rising to the surface from a creek. William Hart, considered as America's "father of natural gas", dug there the first natural gas well in North America.

Throughout the 19th century, natural gas was used almost exclusively as source of light and its use remained localized because of lack of transport structures, making difficult to transport large quantities of natural gas through long distances. There was an important change in 1890 with the invention of leak proof pipeline coupling. However, existing techniques did not allow for gas going further than 160 km. and it was mostly flared of left in the earth. Transportation of natural gas to long distances became practical in the 1920s as a result of technological advances in pipelines. It was only after World War II that the use of natural gas grew rapidly because of the development of pipeline networks and storage systems.

In the early days of oil exploration, natural gas was often an unwelcome by-product, as natural gas reservoirs were tapped in the drilling process and workers were forced to stop drilling to let the gas vent freely into the air. Now, and particularly after the oil shortages of the seventies, natural gas has become an important source of energy in the world.

The gas industry has been highly regulated for many years mainly as it was regarded as a natural monopoly. In the last 30 years there has been a move away from price regulation and towards liberalization of natural gas markets. These movements have resulted in greater competition in the market and in a dynamic and innovative natural gas industry. In addition, thanks to technological advances natural gas can be better explored, extracted and transported to consumers. Innovations also help to improve natural gas applications and create new ones. Natural gas is increasingly used for power generation.