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Using gas ? But what for ?

Last modified: August 2013

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Though we have very quickly taken the habit of protesting against price rises regarding gas, this fuel is the most recent among fossil fuels: only in 1960 did gas use become more important than wood use in the world, when it was 1942 for oil and... 1860 for coal. And for a long time gas was an "american" energy: in 1965, more than 60% of the world consumption was done in the US !

Gas consumption per country or zone since 1965, in billion cubic metres per year. The US used to dominate the world consumption 50 years ago, but it is not the case any more.

Source: BP Statistical Review, 2013

Being a recent energy, the growth rate has been high: the average consumption per capita has been multiplied by 5 since 1945, when it has been "only" 2,7 for oil and 1,3 for coal. In Europe, the consumption has been multiplied by almost 11 since 1965, and in 2011 Europeans paid almost 100 billion euros for their gas.

World average consumption per capita of each significant energy from 1860 onwards, in kWh par year. The rise of natural gas is more recent than the rise for oil, itself more recent than the rise of coal. Incidentally oil has passed the peak of consumption per capita right before the second oil shock.

Sources: Shilling et al. 1977 & BP Statistical Review 2013 (energy), World Resource Institute (population).

One can wonder why gas did not rise at the same moment and at the same rate than oil, since oil fields are very often combined oil and gas fields (and particularly the ones closest to the surface, that have been discovered and exploited first). But contrary to oil, which is liquid and therefore easy to transport over long distances and to store, gas has the bad idea of being... gasesous.

As such, it is much less convenient to transport than oil (the point here is not dangerosity, but really the practical aspect), which translates into the economy through a high capital requirement per energy unit transported. It also explains why 60% of the world oil production is traded internationally, while it is only 30% for gas, and 15% to 20% for coal.

This dificulty to store and transport gas, and the fact that it can seldom be used right on the production site had a simple consequence: until the second half of the 20th century, the gas associated to an oil field was either set free in the atmosphere, or used to enhance oil recovery through re-injection in the field. When the climate scientists discovered that methane was a potent greenhouse gas, oil companies were encouraged to burn all the gas they were not re-injecting into the field (combustion then transforms each molecule of methane into a molecule of CO2, which divides the "nocivity" of emissions by 25), in a flaring unit. All that is mentionned above explains why, when oil companies discovered dry gas fields (fields with only gas and no oil), they considered it as a catastropha, and not at all as good news ! And it is still true when gas is discovered in small quantities far from any existing gas pipe.

And now ? Now gas is used for a number of things:

power plants (25% of the electricity production in the world uses gas fired power plants),

residential and office boilers (for heating),

industrial ovens and boilers,

feedstock for chemical industries (hydrogen production is done through cracking methane - with plenty of CO2 emissions associated - which then allows to manufacture ammonia, then nitrogen fertilizers; there is plenty of oil and gas for real in our plates !),

and a little for transportation (LNG, which means Liquefied Natural Gas).

Breakdown by usage of gas consumption in the world in 2007. This pie chart does not account for the fraction of the production which is flared (roughly 4%), and the fraction re-injected to enhance oil recovery in fields that have both gas and oil (roughly 13%).

Source: BP & CEDIGAZ 2007

As an important fraction of gas is used for heating buildings in the Northern hemisphere, there is a higher seasonnality for gas consumption than for oil consumption (for which the peak happens during the summer holiday season).

Breakdown of the gas consumption per month. The highest seasonnality is for residential use (only hot water and cooking remain in summer), then the second highest is for commercial buildings. Besides part of the electricity production is for peak load, which - by definition - is not constant all year round !

Source: Pierre-René Bauquis, Total Professeurs Associés, 2008

But wells do produce at the same rate all year long, more or less. It means that part of the gas produced must be stored a couple months before being used. Using gas therefore requires storage infrastructure in the consuming country, which is more complex to build and operate than for oil (storing oil requires nothing more than big tanks: no big deal).


Why is gas so appealing now ?

The fast development of gas in heating, industry and power plants is based on a couple of "physical" advantages:

for industrial use, it generates lower local pollution than its competitors coal and oil. It does not contain any sulfur (soluble in oil and present in coal, but not in any gas), which avoids SO2 emissions (that irritates lungs and turns rainwater acid). Burning gas does not generate fine particles, dust, soot, ashes, and actually a full combustion generates only CO2 and water, that are not toxic when emitted into the atmosphere (CO2 emissions induce a delayed climate change, but it is the result of a physical effect, not of a chemical toxicity). But, as for any fuel burnt in the air, we will get nitrous oxides, that are irritants, and that, combined with unburnt hydrocarbons and sun rays, will lead to ozone formation.

Besides gas suppresses storage at the premises of the user (no tank to refill), and costs about the same, per energy unit, than oil products. Because of all these characteristics, factories have progressively turned to gas for heat production (instead of coal or fuel oil). At the present price of gas and oil, electricity is rarely competitive to produce heat, even though there is absolutely no technical barrier to use electrical ovens (besides electricity must not be produced with gas or oil in order for electric ovens to be a good idea, and it must not be produced with coal if avoiding CO2 emissions is the name of the game).

for buildings, gas has about the same advantages as for industries : lower local pollution, no tank to fill, no price difference with oil per energy unit.

for power plants, we have again the advantage regarding local pollution (particularly against coal), but there is another element even stronger: gas has the lowest capital need. Indeed, to install one MW of electrical power (in other words to have a device able to inject up to one MW of electrical power on the grid when at full capacity) it costs 4 million euros with nuclear, 1,5 million euros with a coal power plant, but only 0,5 million euros for a gas power plant. Well, the first thing that counts for a private company to begin whatever project is the capital required to start. As gas has the lowest need, it has taken the first place in new plants in Occidental countries.

Breakdown by nature of primary energy of the power plants in construction in 2007 (in GW, not in number of plants). 100 GW corresponds to the total installed capacity of a country like France. A nuclear reactor = 1 to 1,4 GW ; a coal plant = 0,25 to 1 GW ; a large dam = 0,5 to 5 GW (16 GW for the Three Gorges); a large windmill = 0,005 GW).

Coal comes first in the world, but in Occidental countries (OECD) it is gas. And the first renewable is by far hydroelectricty (that, besides, has a higher load factor than wind).

Source: Platt's World Electric Power Plant Database, December 2008, in World Energy Outlook, 2008, International Energy Agency

In Germany, it's gas and coal that would/will be used to replace most of the phased out nuclear (say two thirds, because the intermittence of wind prevents to go much higher, and it is also true for photovoltaïcs).


All is fine, then ?

Gas seems to be close to a perfect energy, then ! No local pollution, not too much money to put on the table for power plants, and besides it is... "natural" ! And if it is "natural", it is good for us, isn't it ? Of course, all things that are "natural" are not necessarily desirable: asteroids, tsunamis and malaria are perfectly natural... If we wtosk to facts, gas has two major inconvenients:

As a fossil fuel, gas contributes to CO2 emissions that induce climate change. For a given amount of energy, gas emits 30% less CO2 than oil, and roughly 50% less than coal, but still it is not zero: 20% of the world CO2 emissions come from gas. And even if we stick to pollution and accidents, gas is more dangerous than... nuclear energy !

Number of deaths by electrical TWh (and CO2 emissions per electrical kWh) for power generation in Europe. Future casualties linked to climate change are not taken into account. Profesional diseases of coal miners in Europe are significantly less frequent than in non-OECD countries, where the death toll per TWh is higher.

Source: Electricity generation and health, Anil Markandya &Paul Wilkinson, The Lancet, 2007; 370: 979–90.

Gas fields, as oil fields, require hundreds of million years to appear. Gas is therefore subjects to depletion, and will experience the same fate than oil: a peak then a decline. In Europe, the decline has probably begun. So shifting from nuclear to gas in Europe is a debatable idea...

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