What is fracking?

Fracking refers to how the rock is fractured apart by the high-pressure mixture and is the process of drilling down into the earth before a water mixture is jetted at the rock to release the gas inside.

Water, sand and chemicals are injected into the rock at high pressure which allows the gas to flow out to the top of the well.

The process can be carried out vertically or, more commonly, by drilling horizontally to the rock layer and can create new pathways to release gas or can be used to extend existing channels.

Why not Fracking?

The gas is produced and trapped in rock formations following the breakdown of organic matter and has been described as "energy gold" that can boost overall worldwide gas supplies and ultimately reduce costs to consumers.

However, fracking has been linked to a variety of environmental concerns including the contamination of groundwater supplies, air pollution and seismic activity, although there has so far been little consensus on any of the concerns.

While reports have claimed the risk of water sources being contaminated was no higher with fracking than other drilling processes others have cited emissions released into the atmosphere during the process as the cause headaches and breathing problems.

What is happening in Scotland?

A decision on whether fracking takes place in Scotland is likely to be several years away because of legal challenges.

The Scottish Government is due to say this year whether it will permit the controversial gas extraction technique, which could take place across the Central Belt.

However, ministers are expecting the outcome to be subject to a judicial review by whichever side is disappointed, either industry or environmentalists.

SNP ministers introduced a moratorium on fracking at the start of 2015, and the party's 2016 manifesto said it would be banned unless it could be proven "beyond doubt" to be safe.

Scottish Labour is ramping up pressure on SNP ministers to implement a complete ban on fracking with a bill which aims to make the controversial energy extraction process illegal north of the Border.

Who backs fracking?

The UK's trade body for the onshore oil and gas industry has been joined by GMB Scotland in urging Holyrood to lift its moratorium.

UK Onshore Oil and Gas said through the Government's own research "many of the wilder claims about health and environmental impacts have been thoroughly debunked" and continuing the ban was unjustified.

Petrochemical giant Ineos, which owns Grangemouth refinery, is oil one of a number of firms with licences to look for the new fuel across in Scotland, although currently prevented by the moratorium.

It started importing ethane by boat from fracking fields in Pennsylvania last year.