made the top 300, page-17

My take on UCG vs CSM comes down strongly on the side of CSM - here's why:

UCG is a quick and dirty way of monetising an underground coal resource. It's like an inefficient version of a gas works. A conventional gas works produces mostly coal gas (mixture of methane and carbon monoxide (CO)), ammoniacal liquors and coke. The liquids are used as chemical industry feedstock and coke has many uses (blast furnaces, thermal power stations eg). UCG produces coal gas and the coke left underground as a waste product. The coal gas cannot be used as natural gas or CSM substitute as it burns differently and is exceptionally toxic (the CO component).

CSM on the other hand produces pure methane. This methane would have escaped into the atmosphere in the fullness of time in any case - either through conventional coal mining or through natural movements in water tables, earth tremors etc. Methane is interchangable with natural gas (once the NG has been cleaned up) and CSM is available across most of this country - reducing reticulation costs.
Once a coal seam has been exhausted through CSM extraction, holes are plugged, collection equipment removed and the environment returns to normal (leaving the coal available for mining if needed).

The fact that world leaders in UCG are/were Soviet Russia and the apartheid regime of South Africa - neither famed for their environmental credentials tells its own tale.

IMO - when our politicians look closely at the overall impact of UCG, it will ultimately be banned.