If your plan is to recycle old prints, you should try shredding what you have first. That way, you will realize it is ridiculously difficult without spending thousands.
Filament is so cheap these days, it's really not worth making your own with 100% new material (+ colorant) and shredding old prints down to granule size is too difficult to be viable for low volume.
I can give this advice because this is where I'm stuck hah.
I have tried retrofitting paper shredders and blenders and not had much luck getting small, consistent shreds to use in my filastruder (which is also jammed and was always finicky).