Scotland began a consultation on whether to allow unconventional oil and gas extraction such as fracking, its government said on Jan. 31, with a vote expected at the end of 2017.

Substantial amounts of shale gas are estimated to be trapped in underground rocks, and the British government wants to exploit it to help offset declining North Sea oil and gas output.

However, hydraulic fracturing, which involves extracting gas obtained from rocks fractured at high pressure, has faced opposition from environmentalists and local campaigners and was banned in Scotland in January 2015 while the government there gathered information on its potential impacts.

"The Scottish government has a very important decision to make in determining the future of unconventional oil and gas," Paul Wheelhouse, Scotland's minister for business, innovation and energy, said in the consultation document.

"The consultation does not set out or advocate a preferred Scottish government position or policy. Instead, we want to create space for dialogue and allow different perspectives to come forward," he said.

The consultation is open to members of the public as well as industry.

Resources in central Scotland are estimated to hold at least 49.4 trillion cubic feet (Tcf) of shale gas, the consultation said, with about 2% of this likely to be commercially viable for production.

Annual gas consumption in Scotland is about 150 Bcf per year, with about 78% of homes using gas as their primary heating fuel, the consultation said.