A bitcoin miner in Pennsylvania is controversially burning waste coal and discarded tires to generate electricity. This pollutes the air but cleans land. Is that practice wise or not?

It should be noted that only some kinds of cryptocurrency (notably Bitcoin) use the "proof of work" method that entails using lots of electric power. There are other methods.

If burning waste coal to generate electric power is acceptable, it doesn't have to be used for cryptocurrency. It could replace other forms of generation. Thus, the crucial question is whether that method makes more/worse pollution or less/milder pollution. I don't know enough to judge the answer to that.