Natural gas is a gas consisting primarily of methane (CH4, one atom of carbon for four atoms of hydrogen) and is classed as hydrocarbon. Originally, natural gas is gaseous, colourless, odourless (an odorant is added for detection purposes) and is lighter than air.
Natural gas is a primary energy, i.e. energy found in nature which has not been subjected to any transformation. It is produced from the decomposition of plant and animal microorganisms over several million years. It originates from geological underground layers where it can be found as natural gas only (dry field) or combined with oil (mixed field). These fields are generally found at depths of 1'000 to 4'000 metres.
This energy is available and safe. Considered as the cleanest fossil energy, its greenhouse gas emissions are lower. It also has numerous environmental qualities. For example, during its combustion, natural gas hardly emits any sulphur or particles. Potential ash emissions also contribute very little to the production of ozone in cities. CO2 emissions are 25 to 30% lower than with fuel and at least 40 to 50% lower than with coal depending on the process used and the quality of fuel.
Furthermore, natural gas lends itself to very efficient technologies:
upstream, with combined cycle plants which have yields of 55% and cogeneration plants which reach yields greater than 75%;
downstream, condensing boilers which allow an additional gain of 30% compared to traditional boilers. Furthermore, it can be easily combined with renewable energies (solar thermal energy in particular).
Liquefied natural gas is natural gas converted to its liquid form by cooling down to -163°C (cryogenics). Its volume is then reduced by 600. It becomes a light, clear, odourless, non corrosive and non toxic liquid. LNG is approximately twice as light as water.
Following a liquefaction process, LNG is almost pure methane as other components of natural gas have been separated. Carbon dioxide must be extracted upstream of the liquefaction process. If not, it would damage the liquefaction units by solidifying inside the plant. Hydrocarbons heavier than methane are collected and sold as petrochemical raw material or as fuel (liquefied petroleum gas - LPG).
Natural gas is transported by ships called LNG ships. Most LNG ships have a capacity of 140'000 metre cubes of LNG, i.e. approximately 70'000 tonnes, which then equates to 87 million metre cubes of gas in standard conditions.
Once at destination, liquefied natural gas is stored in regasification terminals where it is regasified on demand.
In France, there are methane terminals at Fos-sur-Mer and Montoir-de-Bretagne.
Currently, the LNG market is only active in a restricted number of countries (18 consumer countries and 13 producing countries). The development of new off-shore liquefaction and regasification plants is the key to the expansion of the LNG market. Floating liquefaction platforms can be installed above off-shore gas fields. The gas produced can then be liquefied directly. To this day, there are no floating liquefaction plants in operation or in construction: however potential projects are being assessed in Australia and Nigeria. On the other hand, projects for the development of off-shore regasification units have progressed further. Countries such as Italy, Brazil, the United States, Argentina, The United-Kingdom and Kuwait already have structures in operation.
By 2030, natural gas sales should have more than doubled. LNG will play a decisive role as its contribution to interregional exchanges will go from 52% in 2006 to 69% in 2030, according to the International Energy Agency (IEA). Again, according to the IEA, by 2030, gas transport via gas pipelines could be overtaken by gas transport using LNG ships, as it could reach 470 Gm3.
