Except generating a different kind of "money value", what is the sustainable value of crypto currencies compared to the energy consumed to generate them?
Compared to currencies working with sophisticated papers and metals that have to be changed after some time of use by new notes and coins, crypto currencies do not seem to consume materials. However, they are generated in big data centres that need a lot of power to run. They say that the Bitcoin-System already consumes as much energy like the whole Swiss economy.
As the assumptions of the author were considered as "flawed" I recommend to read his thoughts and study.
I read the other question according to Bitcoins, but think that my question is different to that one, even after having edited title and text, which now allows to discuss above the used technology or algorithms.
As new information of today (Nov. 2018) they (Spiegel) state that Bitcoin consumes more energy than total Danmark. In addition the consumed energy is frequently produced in "dirty" coal power plants.