In a shock announcement, the Eden Project has revealed that it is going to start hydraulically fracturing rocks beneath its site in a bid to extract geothermal energy. They are keen to emphasise the differences between what they are going to be doing and shale gas operations but a glance suggests these are largely distinctions without a difference.
Fracking the rock to create a geothermal heat exchanger is not the same as fracking for shale gas. We will not be releasing fossil fuels for burning. Geothermal developments are much deeper and in granite so there is much less chance of surface damage or contamination to the water table. We have no plans to use proppants or associated viscous chemical fluids to keep the circulation open. France encourages geothermal development but has a moratorium on fracking for gas.
The bit about the developments being "much deeper" than shale is not true. The image on the Eden project puts the depth at something like 4 or 5 km, which is pretty much the same depth at which the Bowland shale sites will be operating. Non-use of proppants - i.e. sand - seems to me to be a diversion rather than a meaningful distinction.
I also wonder if the planners are going to be presented with a dilemma over the noise levels:
Rigs are hired from the oil industry, so drilling will take place 24 hours a day to minimise the cost. It will take around 20 weeks per well. The rig will be one specifically for use in a populated area and heavily soundproofed, producing up to 45dBA at 200m. During operation, the generator will make a constant noise: a maximum of 30dBA at a distance of 200m. But because buildings are low, the noise can be tempered by landscaping.
Readers will recall that similar noise levels were deemed entirely unacceptable for shale gas operations.