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Shale gas fracking Q&ANever mind the spin, what do we know for sure about the

controversial process of fracking?

Fiona Harvey, environment correspondent

guardian.co.uk, Wednesday 20 April 2011 18.19 BST

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Marcellus shale fragments. Photograph: Daniel Acker/Getty Images

What is fracking?

The process of hydraulic fracturing or "fracking" involves drilling a hole deep into

the dense shale rocks that contain natural gas, then pumping in at very high pressure

vast quantities of water mixed with sand and chemicals. This opens up tiny fissures in

the rock, through which the trapped gas can then escape. It bubbles out and is captured

in well that brings it to the surface, where it can be piped off.

Why is it controversial?

Many shale deposits are buried under aquifers, and if the cement casing around the

wellhole is not adequate, then the process of drilling and fracking can release the

chemicals into the aquifer. Leaks of methane can occur, leading potentially to fires or

explosions.

The water-chemical mixture pumped in gradually returns to the surface, where it can

contaminate land and water. It can also be highly saline and contain solids, such as

flakes of rock. Some companies have been accused of poor disposal of the sludge waste

that results from fracking. In addition, the vast quantities of water used can lead to

problems by depleting local ecosystems. There is also concern about the seismic activity

involved in fracking.

These issues have prompted an outcry around the world, and some places are

considering a ban such as Pittsburgh, in the US, while New York called a halt to it

pending a review. A bill to ban fracking in France has widespread popular support.

In the US, legal loopholes mean the fracking industry is poorly regulated, as large parts

of it were taken out of the control of the Environmental Protection Agency (EPA) by

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President Bush, and companies do not have to disclose what chemicals they use.

So what chemicals are used?

Reports in the US have found hundreds of chemicals in use, some of them potentially

toxic, including methanol, naphthalene, benzene and lead. In the UK, shale gas

company Cuadrilla Resources uses only three, including a lubricant commonly found in

cosmetics, hydrochloric acid, and a biocide commonly used to purify drinking water.

Should we be worried?

Owing to the legal situation in the US, where fracking has been pioneered, and the

secrecy of the fracking industry, it has been hard to gauge how dangerous fracking is

and whether the processes can be controlled in such a way as to make them safe. But the

US the EPA is currently undertaking a massive study of the industry, so there may be

answers from the preliminary report by the end of next year, though the full report will

not be available until 2014.

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