I am sorry to say that people propose filament recycling to me often enough that I now have a policy that I will not discuss it further until the interested party can show me that they have recycled 10 kg of filament.
This is not because I think it’s a bad idea. I think 3D printing is an environmental nightmare, and I would love to see the problem solved. Unfortunately, most people who want to talk about it never get anywhere, so I’d rather not spend the time to go through what has proved to be a futile exercise thus far, unfortunately.
Here are some other statistics that could be useful: in the Tufts School of Engineering, we have around 17 3D printers in regular use. Most of them are Prusa MK4’s printing PLA. We buy around 500 rolls of filament per year for around $20 each. This is at least 80% of the 3D printing that happens at Tufts. There is some fancy SLA printing that happens in the Tufts Dental School, but I think that’s relatively low volume.