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A ban on chemically transforming underground coal into synthetic natural gas has been imposed.

Natural Resources Minister Carl Sargeant has imposed a moratorium on underground coal gasification (UCG).

Mr Sargeant said this forms part of a "precautionary approach" towards the development of unconventional oil and gas resources, which includes a temporary ban on fracking.

Any council not proposing to refuse an application must refer it to ministers.

Mr Sargeant said: "The direction has been issued to require that any planning application connected to the gasification of coal must be referred to Welsh ministers where local planning authorities are minded to approve them."

It applies to any onshore application registered on or after 25 March and Mr Sargeant said it was to "avoid any ambiguity".

A study by Duke University in the US suggested synthetic natural gas emits seven times more greenhouse gases than natural gas and almost twice as much carbon as a coal plant.

Underground coal gasification