Energy is not the biggest concern. Entire data centers (such as Microsoft’s Azure data centers) are running entirely on clean energy (that’s right — zero percent carbon footprint). There’s no reason a mining rig couldn’t.

In addition, if you truly talk about replacing centralized banks (I am not saying bitcoin will), you have to account for the electricity and paper currently being consumed by centralized banks, as that is what the bitcoin network will replace.

Lastly, every technology that can be used for good, can be used for bad. The same is true of traditional currencies — euros, dollars, credit cards. The 9/11 hijackers made all their purchases using regular bank issued credit cards — so much for all our ‘tracking’ technology. In fact, owning bitcoin is probably going to get you noticed. In the U.S. at least, you need a KYC process to go from dollars to BTC or vice versa — there is no way to bypass that. The same is true for most developed countries.