Recycling filament is more difficult that one might assume it is. You'd have to make sure you kept different materials separate. There are extruders out there, but they aren't super cheap. I have considered designing an DIY extruder in the past, but the logistics usually haven't worked out for me to continue.

I almost see it like buying a bread-maker or pasta-maker for your kitchen. The idea is great and you get all excited to use it, but after that initial enthusiasm runs out you just head down the street and pick up a loaf of bread of box of spaghetti instead because its easier.