You asked a very good and important question. I don't want to share the answer, but know that it explains a very important topic on economic systems.

Since I'm not going to be giving away the answer, I want you to at least ask yourself:

Does the practice of pressing buttons and printing dollars provide value at the value the units represent?

And since your concern seems to be the environmental cost of bitcoin mining, what are the environmental costs to pressing buttons on a computer adding dollars into a digital dollar network along with running printers to create a few sheets of paper money?

Are there any environmental costs beyond the electricity that runs the printers and the computer and the trees cut down to print the money on?

If so what would those environment costs be and where would they be coming from?

If not, where is the value of that dollar coming from to begin with?