A government strong enough might have the ability to control Bitcoin mining over the holders, but breaking decentralization in this way will kill Bitcoin in its fundamental, and it seems that no such government is going to do this for now, especially when the reason is "environmental problems", which is generally not in high priority. Beside this idea, maybe a BIP (Bitcoin Improvement Proposal) is the best way of achieving consensus, but I can't imagine such a proposal being approved based on its limited feasibility.
What seems possible is to check what miners mined a block, and externally verify their footprint. But I don't think there is a decentralized way to do it. An entity certifying "green miners" would be a centralized authority.
Bitcoin are being traded by energy companies to subsidize their infrastructure and improve energy efficiency and capacity.
In some ways Bitcoin is a battery, because hydro dams don't idle generators as often they can sell their excess energy production and subsidize the dry season. Oil companies capture the natural gas flares and use it to power generators to mine bitcoin, etc. There really only needs to be one POW coin, and I think it's pretty obvious that Bitcoin is it.
proof of work is the only thing that maintains unforgeable costliness.
Every proof of stake system eventually centralized and failed.
And of course proof-of-work isn't necessarily immune to wealth centralization either.