Extracting shale gas near Blackpool by "fracking" almost certainly caused two minor earthquakes earlier this year - but could it hold the key to the UK's energy future? Channel 4 News investigates.

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"Fracking" is a controversial method of extracting gas reserves from deep underground. The "fracking" or "hydraulic fracturing" process involves using a high pressure jet of water, including chemicals, to fracture rock deep in the earth to release shale gas.

In the United States, it already counts for around 25 per cent of domestic energy production. But the process is banned in France, and campaigners warn that it has dire environmental consequences. These include claims in the US that the gas has bubbled into drinking water - with some people able to set fire to water coming out of their taps.

Now a panel of experts has concluded that the first attempts to embrace the method in the United Kingdom caused two minor earthquakes earlier this year in one of the more seismically sleepy areas of the world - the Fylde coast in Lancashire.

We are now scraping the bottom of the fossil fuel barrel. It's 'extreme energy' now - all the easy stuff is gone. Frack Off spokesman

The earthquakes, both measuring less than three on the Richter scale, hit the area after oil and gas firm Cuadrilla Resources began drilling for gas in the region, and fracking at one of the company's three sites.

However, the report also suggested that the earthquakes were due to a specific and "unusual" combination of factors which were unlikely to recur - and even if they did, any "seismic events" would also be similarly small. It also proposed putting in an early detection system to reassure the community.

The chief executive of Cuadrilla, Mark Miller, said he was pleased that the report, which was commissioned by the company, found that there was "no threat to people or property in the local area from our operations", and said it was ready to put in place an early detection system.

He added: "Cuadrilla is working with the relevant local and national authorities to implement the report's recommendations so we may safely resume our operations."

The report has been submitted to the Department of Energy and Climate Change and the British Geological Survey for further study.

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As the report was published, experts gathered in London for a summit discussing whether shale gas is the saviour for the energy market. At the same time, back in Lancashire, protesters scaled one of the drills at Cuadrilla's Banks site, near Southport, to highlight their concerns.

Shale gas is clearly a topic which splits opinion. But what are the pros and cons of the industry, still in its infancy in the UK? Channel 4 News hears from both sides.

'Frack off'

Campaigners say fracking is a dangerous process, and shale gas itself is a damaging fossil fuel.

Protesters from the Frack Off campaign group entered one of Cuadrilla's sites, near Southport, at 5.30am this morning before four of them climbed the drill to protest against shale gas and fracking.

Read more on shale gas: Striking 'gold' in Blackpool?

They are also holding a "frack mob" outside the London conference to, they say, "highlight the hypocrisy" of the shale gas environmental summit.

A spokesman told Channel 4 News that it was wrong to focus on another fossil fuel - shale gas - when the world needed to tackle climate change.

"The underlying objection is that it's another fossil fuel at a time when we should be looking at how to go forward in a sustainable future," he said.

He also said that fracking is very damaging to the environment in a more immediate way.

"We are now scraping the bottom of the fossil fuel barrel. It's 'extreme energy' now - all the easy stuff is gone. And it's not just the indirect damage fracking does to climate change, it's direct damage to the land around it - chemicals in America escaped into people's water, there was air pollution, and now we have a report confirming earthquakes were probably linked to fracking," he told Channel 4 News.

However, energy market expert and shale gas advocate Nick Grealy of consultancy No Hot Air said that the earthquakes were "imperceptible".

"It's worth noting that in the original Richter scale, Richter himself didn't think anything under three could even be measured. People would be in their beds, asking themselves: 'Was that a 1.5 earthquake, or the cat flap?'" he said.

However, he said the shale gas industry understood people's concerns and would work with them. Cuadrilla also said in a statement that it had been "very open" in showing people around their sites in Lancashire.

People would be in their beds, asking themselves: 'Was that a 1.5 earthquake, or the cat flap? Nick Grealy, energy expert

Environmental risks

Mr Grealy said the environmental risks were negligible compared with the benefits of shale gas.

He said: "Yes, it is a fossil fuel, but it is at least 50 per cent less carbon intensive than coal. The real enemy here is coal - and if we continue talking about gas, we are ensuring that more and more coal is burnt. Realistically, in many parts of the world it is going to be gas or coal."

He also said the environmental risks in the UK, including air pollution and water pollution, were already addressed by current regulations and even the Environment Agency had concluded it was not an issue.

Mr Grealy added: "We have been through a number of stages: ignorance about shale gas; now we are in a situation where people are in denial - 'oh it wouldn't work, we don't have that much'. What the UK debate needs to do is have a 'what if' these things, which are optimistic, come to pass."

He said it isn't yet clear if shale gas will be a bridging fuel until the question of how to replace fossil fuels is solved, or if shale gas itself will answer that question.

But for the moment, beyond the environmental debate, there is a pressing economic argument for shale gas, he told Channel 4 News. Other fuels are running out and the UK cannot, yet, rely on renewable technologies. So if the debate continues with no more action, the UK could be forced into using shale gas anyway - but it will miss out on exploiting its own natural resources.

"The reality here is that if we don't use UK shale gas, we are going to end up importing US shale gas," he warned.