Q: What is "fracking"?
Fracking - or hydraulic fracturing, to use the proper term - is the extraction of shale gas through drilling a well hundreds of metres underground and filling it with water, sand and chemicals. The practice has been halted in the UK since it resulted in two minor earthquakes in Blackpool last year; however, the advice of an official British government report published today advised ministers to continue fracking - in a move that could result in thousands of new wells being drilled all over the country.
Q: How much gas does it produce?
According to the Department of Energy and Climate Change (DECC), the stage of the fracking process in the UK means that it is too early to decipher how much gas can be extracted. A statement on their website says: "None of the wells drilled has been production tested, so a reliable reserve estimate (the amount of gas that can be technically and economically produced) cannot yet be made."
However, a DECC-comissioned British Geological Survey (BGS) in 2010 estimated that 150bn cubic metres of shale gas could be recovered through fracking; such a volume would account for two whole years of gas consumption in the UK.
Q: What do its advocates say?
Burning natural gas produces far less CO2 and other pollutants than using coal or oil - as those in favour of fracking like to remind us. In the US, where shale gas is estimated to account for 46 per cent of natural gas production by 2035, fracking plays a major part in fulfilling the country's carbon reduction targets.
Dieter Helm, Professor of Energy Policy at Oxford University, said in a report published last year:
"With the coming of shale gas, the conventional wisdom has been turned on its head: there is now so much potential gas that for policy purposes it is better to assume that supplies have the potential to exceed demand for the period right through to 2050 and indeed for the rest of the century."
Q: What do its opponents say?
Opponents point to the large amounts of flammable methane gas - an asphyxiant which can displace oxygen in an enclosed space - that have leaked from extraction sites and could potentially get into drinking water. The new report claims this can be avoided.
Environmental campaigners also say that gas extraction won't necessarily reduce global coal use; the Tyndall Centre for Climate Change Research recently concluded that unless there is a global carbon cap, additional gas would only add to overall fossil fuel use.
Thirdly, green groups are concerned by the large amount of water required to extract shale gas through hydraulic fracturing. Many see this as a waste at a time when there is a global water crisis.
Safety issues also arise. The report accepts that the Blackpool earthquakes - measuring 2.3 and 1.5 on the richter scale - were the result of fracking in the area. Peter Styles, a professor at Keele University who wrote the report, warned that further fracking around Blackpool would lead to increased seismic activity.
Andy Atkins, the Executive Director of Friends of the Earth, said: "We don't need earth tremor-causing fracking to meet our power needs – we need a seismic shift in energy policy. There should be a full scientific assessment of all the impacts of fracking – a short consultation on one of the problems is completely inadequate."