Why is natural gas considered a cleaner source of energy?
What is natural gas?
How is it measured?
What is methane?
How is natural gas formed?
Where is it found?
How is it extracted?
How is it transported?
What is liquefied natural gas (LNG)?
Is natural gas polluting?
Why is natural gas considered a cleaner source of energy?
Natural gas, with its particular chemical and physical characteristics, is considered to be one of the cleanest sources of energy currently available. Numerous studies have shown that when burnt natural gas produces lower quantities of pollutants like CO2 and nitrous oxide and negligible amounts of sulphur oxides, thereby contributing to improve the quality of the atmosphere and the environment.
What is natural gas?
Natural gas is a fossil fuel made up of a blend of hydrocarbons, primarily methane (90-95%) and is therefore commonly known as methane or methane gas. It normally also contains heavier gaseous hydrocarbons such as ethane, propane and butane, as well as smaller quantities of pentane. There are also modest percentages of various gases such as carbon dioxide (CO2), nitrogen, oxygen (traces), nobles gases and hydrogen sulphide. Some of these gases have to be removed by chemical processing before the gas is fit for normal use. In Italy, natural gas typically contains 99.5% methane, 0.1% ethane and around 0.4% nitrogen.
How is it measured?
Natural gas is measured by volume at standard temperature and pressure (1 ATM and 15°C). The unit of measurement used is the cubic metre, and the volume is normally expressed in thousands, millions or billions of cubic meters. Natural gas can also be measured in terms of calorific value, expressed in kcal/Sm³ (kilocalorie per standard cubic metre) or in MJ/Sm³ (MegaJoules per standard cubic metre).
What is methane?
Methane is a simple hydrocarbon found in nature in the form of a gas. A molecule of methane consists of one atom of carbon and four of hydrogen and takes the formula CH4.
How is natural gas formed?
Natural gas is a fuel of fossil origin formed, generally together with petroleum, hundreds of million of years ago by the chemical decomposition of organic substances (such as algae, plankton) in the absence of oxygen. Fossil fuels are formed when organic matter, mixed with sand and clay muds, is compressed beneath layers of sediments deposited one on top of the other. The very high pressures and temperatures deep in the earth break down the chemical bonds in organic substances to form hydrocarbons. Natural gas can also be formed by the transformation of organic matter by micro-organisms and the gas produced is called biogenic methane. The micro-organisms responsible for creating biogenic methane are commonly found close to the surface of the earth's crust, but they also live in the intestines of most animals, including human beings.
Where is it found?
Once formed natural gas tends to rise to the earth's surface through layers of friable clay and other material. Some of this gas reaches the surface and is released into the atmosphere. However some may find its way into geological formations that trap the gas underground. These normally consist of layers of porous sedimentary rock (which absorb the gas rather like a sponge), and a denser impermeable surface layer. The impermeable rock traps the gas and, if the formations are big enough, form underground deposits. Today around 57% of world gas reserves are found in 190 "super giant" and "giant" deposits; 15% in 200 large and medium deposits and 28% in over 24,000 small deposits.
How is it extracted?
Natural gas deposits are discovered using seismology. Seismographs are used to record the rate of propagation of artificially generated seismic waves as they reflect off the various geological layers. This gives us a picture of the stratigraphy and structure of the rock down to a depth of several kilometres. One an exploitable deposit is found, the extraction plants are built numerous wells are bored. The wells are then connected to a main collector by a network of pipes.
How is it transported?
A complex system of pipes is used to transport the gas quickly and efficiently from the wells to areas of greatest demand. There are essentially three types of transport system: collection systems, domestic / international pipelines and local distribution networks. A collection system consists of a network of low pressure, small diameter pipelines which carry the crude natural gas from the well to the processing platform. Domestic and international pipelines carry gas from the extraction zone either to national distribution centres or to foreign countries where needed. However, pipelines are not the only way to transport natural gas. Over very long distances natural gas can also be transported in liquid form as LNG (liquefied natural gas) by tankers to a growing number of terminals around Europe. At destination the LNG must be re-gasified in special re-gasification plants before injection into the domestic gas network of the consumer country.
What is liquefied natural gas (LNG)?
LNG is obtained by condensing natural gas into a liquid by cooling it to a temperature of -160° C.
Is natural gas polluting?
Natural gas is not toxic to humans, animals or plants and does not pollute water, soil and subsoil. Also in the case of leakage in water or in the subsoil, natural gas does not pollute.