I may have responded to the wrong person.
The main point was to take it off the market. It would not be available to the market by the time the price may have been practical due to diminishing supplies of the cleaner burning coal.
Anytime a portion of a non-renewable resource is made unavailable it increases the value of what remains. That is why there is a "oil depletion allowance" to deduct the increasing cost of retrieving an energy source. In the existing tax code, certain oil, gas, coal and uranium producers receive a huge subsidy through the percentage depletion allowance.
I could stand corrected, but I believe the "oil depletion allowance" went the way of the Dodo bird as part of Carter's assault on "excess profits" in the '70s. Since the demise of the allowance, there hasn't been any "depletion" of oil reserves at all! Oil reserves have increased annually ever since, as the Oil companies were forced to earn money through the production of oil, rather than through a tax gimmick.