I agree, we should stop generating electricity using fossil fuels.

That said, I don't think it's right to just short the connection between "coal" and "bitcoin", we aren't mining coal to get bitcoins, it just so happens that majority of the electricity generated is through coal and mining uses electricity, so does our conversation on the internet.

> And the legacy systems from barter to bitcoin are all still around.

I'm not sure I get your point here. At some point, money of any form will be exchanged for goods or services.