Just focusing on PoW via nuclear power production, we can power the Bitcoin blockchain for centuries, if not millenia, on clean nuclear energy. This hand-wringing about Bitcoin PoW is hysterically overblown, and amounts to a proxy argument about our inability to generate clean energy while ignoring our ability to generate clean energy.
[1] https://www.statista.com/statistics/1200477/bitcoin-mining-b...
[2] https://en.wikipedia.org/wiki/Nuclear_power_in_China
[3] https://en.wikipedia.org/wiki/List_of_countries_by_uranium_r...