This aspect of bitcoin energy and the environmental impact had been discussed already on a mega thread created by fillippone https://bitcointalk.org/index.php?topic=5325350.msg56613804#msg56613804 if you can go through the discussion, you will discover that bitcoin has in many ways being a solution to the environment than contributing to the environmental disaster in it, bitcoin mining might be proof of work but it's not the problem to the hazard in the environment, rather it is providing more solution to this lingering environmental challenges through bitcoin mining, you can discover more on the thread link provided above.