It may be relatively clean compared with other fossil fuels, but natural gas still produces greenhouse gases and is far from sustainable

You can't see it, taste it or smell it, but given the current cost of natural gas, you can certainly feel its impact on your wallet. Like oil and coal, natural gas is a fossil fuel consisting of various combustible hydrocarbon molecules - chains of hydrogen and carbon - the vast majority of which is methane. It is created through the decay of organic matter such as plants and animals over the course of millions of years. Geological pressure combined with high temperatures are the catalyst for this transformation, causing the carbon bonds in this organic matter to break down. Although often found alongside oil fields more than a mile deep, generally speaking the deeper you drill, the more a field will primarily consist of gas and sometimes even just pure methane. Despite its name, natural gas can also be used and transported in liquid form. Compared with other fossil fuels natural gas burns relatively cleanly, although it still produces the greenhouse gas carbon dioxide.

Natural gas has a slightly higher energy density than petrol - nearly 13 times that of dynamite. With the decline of the British coal industry, gas has become a major source of electricity production. It is also used as feedstock for producing a range of chemicals. But most of us are more familiar with its use to heat homes and as fuel for ovens and hobs.

The trade-off to this is safety. Much of the damage caused by the earthquake that hit San Francisco in 1906 has been attributed not to the quake itself, but rather to fires from ruptured gas lines.

And storage and transport of natural gas, which has a naturally low density, remains expensive. While pipelines can be economical, they are impractical to transport gas across oceans. In light of the high value of gas, the industry is increasingly taking to transporting it in liquid form, either through pressurisation or using chemical processes to produce what is known as liquefied natural gas.

The Middle East is currently the largest source of gas, but dwindling energy supplies and high demand has led the industry to start looking elsewhere. Most gas is recovered alongside oil, or in natural gas fields that typically occur at greater depths at high temperatures. But the industry has increasingly been getting natural gas from coal-derived methane and other less profitable sources such as gas shales. It is even starting to curb the wasteful practice of gas flaring. This is where, in some cases, gas found next to oil is considered to be too expensive to recover and is simply burned off into the atmosphere, to the detriment of the environment.

Conservation

Besides its greenhouse effects, the use of natural gas also poses conservation issues. The Sakhalin oil and gas offshore platforms on the east coast of Russia have been accused by conservationists of threatening the survival of the grey whale, a species already perilously close to extinction.

Like oil, natural reserves of gas are running out. Some predictions estimate that global supplies will peak within a couple of decades and dry up before the end of this century. Meanwhile, consumption is on the increase, pushing prices up. Fortunately, there are alternative ways to generate electricity and heat our homes, such as by burning hydrogen instead, provided non-fossil fuel sources of hydrogen can be found. Another option is to take advantage of our landfills. When the high biomass content found in landfills decays in the absence of oxygen it gives off methane. Landfills in Europe alone produce close to 100bn cubic metres of this gas each year. Yet currently only about 1% of this is being tapped. However, given that current consumption of natural gas is about 30 times this figure, and that there is no infrastructure to capture and process gas from landfills, a significant amount of investment, and a lot more rubbish, would be needed to meet the growing demand.