I don't know why this new sustainability saga is going around the World. Almost every business these days have to showcase their contribution to environment. I don't think this is wrong but to be true most of it is just a sham and actuality is far away from truth. Companies often say false in these statements. Talking about bitcoin the only way it can be energy efficient is if it shifts to mining using only and only renewable energy methods which is very difficult considering most of the mining is still done in developing nations, other way out is to shift to pos which will defeat the very purpose of bitcoin so makes no sense to shift on that as well.