The potential for fracking shale gas in the UK is huge.
A recent study by the British Geological Survey suggested there could be as much as 1,300 trillion cubic feet of shale gas in the north of England alone.
The UK consumes about three trillion cubic feet annually. But where scientists disagree is how much of those reserves could be extracted.
Some experts say around three per cent could be easily recovered - that would supply the UK's total gas demand for a decade.
There are many hurdles to overcome. Some are geological ones: where is the gas; how much can be accessed; what regulations might the government impose?
But the biggest hurdle will be one of public opposition.
There are concerns about contamination of the water supply; about the potential for earthquakes; about the chemicals pumped underground; and the number of lorries which will be needed to transport materials to and from fracking sites.
It's why the Government is being accused of bribing councils with its announcement today that they can keep 100% of the business rates from any shale gas wells.
So until public unease over fracking can be addressed, the opposition to a potentially large reserve of cheap energy will remain.