Some facts:

* Proof-Of-Work is dirty because the energy-grid is dirty.
* Banning proof-of-work will not clean up the energy gird.
* Cleaning up the energy-grid /would/ clean up proof-of-work.
* A buyer of last resort for energy can increase the viability of new energy projects.
* Unless we build new energy projects, we will burn all the coal.
* Coal that stays in the ground can't be used for proof-of-work-mining.
* Subsidizing energy projects cheaper than coal can keep coal in the ground.
* Proof of stake is just more oligarchy.

Hot take:
Bitcoin is greener than Tesla.