The carbon dioxide pollution caused by BTC mining is almost negligible compared with the traditional industrial carbon dioxide production!
Compared to the exploitation of oil, gold mining, BTC mining is very environmentally friendly!
I think electricity is not really a problem in Bitcoin mining because there are so many invention today that can really help our mother earth and in terms of electricty we can now use solar panels to generate electriciy and you don't need to burned trees or use gasoline that creates smokes.