A recent study led by Robert Howarth of Cornell university suggests that greenhouse gas emissions from shale gas may be twice that of coal.

The study examines the total emissions associated with the extraction and combustion of the gas, particularly the levels of methane (a significant contributor to climate change) that leak into the atmosphere during extraction and transportation. It finds that low estimates of emissions involved with shale gas are comparable to coal, and high estimates up to double those of coal. The authors note the high degree of uncertainty over levels of methane leakage, something which industry commentators have been quick to jump on (see here for a critique of the paper and Howarth's response). Part of the reason for the uncertainty is the gas industry's unsurprisingly lax attitude to methane leakage measurements.

Shale gas is natural gas trapped in bubbles within shale, a type of sedimentary rock. Its extraction involves using a hydraulic fracturing technique ('fracking'), where a mixture of high pressure water and chemicals is injected into the shale, fracturing it and thereby releasing the gas.

It has been identified as a major new energy source with James Smith, outgoing UK chairman of Shell, saying the company will go from being an oil business to a gas producer. "Estimates show that we could have enough gas to power the world for 200 years," he said. Already widely adopted in the US, and with nuclear on the back foot, soaring oil prices and vast shale gas reserves estimated in various places around the world, conditions are right for rapid global development. All of this is hugely damaging for renewables, as shale gas is heralded by governments and the fossil fuels industry as the 'low carbon' replacement to oil and coal.

Emissions are not the only concern however, the U.S. Environmental Protection Agency (EPA) announced that it will conduct a study to investigate the potential adverse impacts hydraulic fracturing may have on water quality and public health, amid widespread concerns about contamination of ground water with toxic chemicals. Some have called for a UK Moratorium of shale gas operations until the investigation is complete. Not only this but recent studies by the Arkansas Oil and Gas Commission suggest that fracking may be behind the spate on mini-earth quakes hitting the area.

The industry has been aggressively lobbying for the adoption of shale gas in Europe instead of renewables. At the same time, it has anticipated resistance and attempted to gain a foothold before opposition has a chance to organise, particularly following the success of the US documentary Gasland. Some countries, such as France, have had successes with anti shale gas campaigns. In the UK, Cuadrilla Resources have recently completed the first attempt to extract shale gas, near Blackpool, Lancashire.

Next month Corporate Watch will be looking at various companies involved in shale gas extraction and the growing grassroots resistance to them.