Chia is a great project, but proof of space and time is just another expression of proof of work. In this case the work is to procure disks, which are made from stuff, toxic stuff. I don’t think an environmental argument for chia works, no solar/wind farm can magic up Silicon for SSDs.
SSDs aren't required for Chia, they're just faster for plotting which is a one-time process anyway. Once plots are made they can be "farmed" (mined) indefinitely for the energy cost of idling drives. So the environmental cost is an up-front capital cost instead of an ongoing power cost which in my opinion is a lot better. And this is not to forget that the storage market is already huge anyway and that "procuring drives" can be used for storage other than Chia, whereas the energy wasted by ASIC Bitcoin miners is just a complete waste.
