No. There is not.
In fact, it is scary to me that rising wealth inequality at the top make it possible to consider buying out and shutting down the entire U.S. coal industry for environmental reasons. “Only” fifty billion dollars? Private wealthy individuals making social decisions of that magnitude? Frightening.
It is unlikely to happen. First, usually when somebody tries to buy a company they have to offer more than the current market capitalization. The reason is that the price represents the marginal seller of shares. When the demand for those shares goes up, as happens when you want to buy a controlling stake in a company at once, the price goes up. So even if the $50 billion number correctly represents the market capitalization of all current coal companies, the price to buy a controlling stake would be higher.
Second, there are other costs. Much of the assets will have very little realization value, but the debts will need to be paid. There may be other hidden costs: cleanup, for example.
Finally, if one group can bid for political reasons, another group can counterbid for political reasons. That will also serve to drive up the costs.
In short, it is a provocative idea, but having environmentally-conscious rich people buy out the coal industry is (a) terrifying in-and-of-itself; (b) more expensive than advertised; and (c) is a game that other more-evil rich people can play.