How is it possible to frame those systems as green?
It's power that goes away to computation
It's hard disks that nobody uses and that sit there, eating power
All those things have not only the energy cost, but also the environmental, production costs associated, and the damage done to countless companies that can't get the hardware anymore
Things are not either "green" or "not green". Something can be "more green", and just because it's not perfect doesn't mean we shouldn't go down that route instead.
The fact of the matter is that cryptocurrencies are not going away.
You can choose to be angry and resentful of that, or we can try to find ways to minimize the impact they have overall.
Hard drives use a fraction of the power that a CPU/GPU/ASIC uses, and there is just as much production energy and waste involved in those as in hard drives.
The world is not black and white.
This problem will only get worse, so finding productive use cases for this capacity is great.
While I think bitcoin makes some sense, I personally think the new coin Chia could make even more sense. "Farming" (aka mining) chia is very energy lite - but it does require "plotting" which is more energy intensive. If plotters run during the inexpensive energy periods and low cost farming is the only thing that runs during the peak energy cost periods, then the network wouldn't see huge fluctuations in mining and leave more vulnerable during periods of low mining and high energy costs.