I did a whole heap of research about recycling FDM filament for a university assignment last year. I'll add my two cents, albeit it sadly doesn't do much to answer your question Tahu.
Like Sgt Saint said, it's very hard to recycle filament. Firstly, as we know, filament is very tempremental and any slight flaws can cause a defect in the print or stuff up the printer, like a clog. That means any foreign particles (ie. dust), moisture, mixture of different filaments - or even same filament but different colour - that gets recycled can end up jeapardising the end result. So it's quite tricky to get it all prepped.
After each "life" that plastic gets recycled, it starts to lose its materialistic properties. After plastic gets recycled over and over, it becomes inconsistant and behaves much differently to virgin material, thus becoming unreliable.
That's uh... that's all I can remember right now at 11pm about an assignment that I finished a year ago. I also did a bit of research on the ability to break down plastics in composte. I'm happy to go back over my research if anyone wanted to discuss it further.