[evilduck]

Something like a PET milk jug is harder since you’d need to shred it and remelt a good portion of the jug into filament since the handle area would be hard to deal with, which is hard to do in a DIY manner. Same for reprocessing failed prints and scrap support pieces of prints, plus various coloring agents and manufacturer additives make a blend of recycled bits inconsistent. It’s probably easier to DIY a high temp composter than to recycle PLA.

But there’s a ton of people out there with jig designs to spiral cut a normal cylindrical bottle and feed it into a hotend that creates filament from it. Here’s one example https://www.printables.com/model/768657-petalot-plastic-bott.... YouTube has dozens of videos of these in action. Generally speaking you won’t get as good of results as commercial filament since filament diameter needs to be carefully controlled and it affects flow rate which then affects resulting print quality. If you print something simple, large, and practical it’s fine, if you need something finely detailed it can be fiddly.