I recently picked up a garden shredder on ebay for 15€ in the hopes I can misuse it for shredding plastics. This should then be fed to my Filament Factory to create 3D printer filament.
The Einhell EGC 2400 has a 2400 Watt motor. Plenty of power to shred branches and plastics. I went with Polypropylen flower pots. At my local florist I asked for those old pots and got a whole load of the precious resource.
I made some pictures and a video of the outcome. The shredder had no problems processing the pots but the pieces are still too big even after shredding them twice. See for yourself.