Reliably combustible, easy to transport and store, relatively clean and still abundant, natural gas is one of those hydrocarbons that should be with us for a long time.

Created by decomposition of organic materials (plants and animals), natural gas is a mixture of light hydrocarbons containing mainly methane (CH₄: carbon and hydrogen), but also propane, butanes, pentanes and other compounds, such as CO₂, helium, hydrogen sulfide and nitrogen. The actual proportions vary from deposit to deposit. This colorless, odorless and tasteless gas, which has no clear form and disperses readily in air, seems hardly designed to attract attention. In fact, for many years, we used it very little and not very wisely, content to burn it only to light gas lamps, while fearing its unwanted presence (methane explosions in mines and accidents in the home and workplace). But, since the 1920s, we have been learning how to appreciate it and to exploit it to our own advantage.

60 years of reserves

One of the main advantages of natural gas is that it is the most widely distributed fossil fuel on the planet, occurring in natural underground reservoirs or "pockets" (often above oil deposits) and even beneath the ocean bed.

Estimates of reserves can only be approximate, since constantly evolving exploration techniques bring new discoveries almost daily, increasing the quantities available (assuming a constant exploitation rate). However, according to CEDIGAZ, the international association for natural gas, with an available volume of nearly 180,000 billion cubic meters in 2004, proven reserves are sufficient to meet current production capacities and growth for at least the next sixty years. CEDIGAZ also estimates that there are 104,000 billion cubic meters of additional known reserves available for exploitation.

It is interesting to note that the ranking of producing and exporting countries does not reflect the map of "proven" natural gas reserves. For example, the United States, which owns only a small proportion of these reserves (4%), is the world's second largest producer, but only a minor exporter, since it uses almost all of its production domestically – in addition to absorbing almost all of Canada's exports! Russia, on the other hand, which is number two in terms of reserves and number one for production, exports up to 30% of that production, mainly to the European Union. Then comes the Middle East: though its potential is the largest in the world, the region is focused – at least for now – on oil.

An energy source well suited to developing economies

Natural gas has been the fastest-growing fossil fuel over the past thirty years. It has earned its place in the global energy mix through the sheer number of applications to which it lends itself, some of which are still in development, such as hydrogen reforming.

Employed largely for domestic cooking and heating, it is also widely used by industry in a broad range of production and conversion processes. Gas-fired power plants are fast to build, easier to maintain and less polluting than those that burn other fossil fuels. Such considerations make this energy source well suited to developing economies with an urgent need for power. Combined cycle plants (not to be confused with cogeneration plants) recover heat from the gas combustion process to feed a second turbine, thus generating more electricity. For power generation, natural gas is an attractive option in terms of capital investment and operating costs. Nevertheless, the high cost of this fuel makes power generation more expensive than the nuclear option. Lastly, it constitutes an economical and less polluting fuel for vehicles when compressed or liquefied, especially in the form of a recently introduced and very promising product called GTL.

A less polluting fuel

The fact that natural gas can be liquefied is one of its greatest assets in terms of transport and storage. But it has many others, including the fact that it is the least polluting of all fossil fuels in terms of the greenhouse effect, due to its low carbon content. Burning it releases virtually none of the sulfur dioxide responsible for acid rain or solid/unburned particulates. Overall, and for an equivalent quantity of energy, it releases from 25% to 30% less CO₂ than oil products and half that of coal, but 23 times more than wind power and 29 times more than nuclear power. Injected into coal- or oil-fired boilers, it reduces NOx (nitrogen oxide) emissions by 50% to 70% and CO₂ emissions by 20% to 25%. Natural gas burns readily with a narrow flammable range, which makes it safer than other fossil fuels. On the other hand, its calorific value, measured in BTU, varies according to the pressure applied and the methane content, since methane accounts for more than 80% of its energy potential. As with other fossil fuels, the intrinsic properties of natural gas vary from deposit to deposit.

Joining nuclear power

The fight against global warming opens up new prospects for natural gas, which is a major hydrogen donor by definition. But to do this requires economically viable vapor reforming technologies that can be applied to gas to extract its hydrogen. These technologies then need to be combined with equally economic – and completely safe – carbon sequestration solutions, which are vital if natural gas is to join nuclear power in the tightly-knit circle of competitively-priced carbon-free energies.