To Bettina, here an example about how obtain rudimental molds: https://www.youtube.com/watch?v=s4ogH-1RMwc Other considerations to this point you can do with the Rotational Moulding technique...
And here a link to make bioplastic at home: https://www.youtube.com/watch?v=5M_eDLyfzp8
Thanks Paul to your further links, expecially this one: https://www.youtube.com/watch?v=UEqshpJZT-A It supports the intention to replicate the shredder machine working in conjunction with a 3d printer!!
Yeah, in these versions (previously reported) with the same mechanism it is possible to shred by hand or with electricity.
There are a lot of "Filabot" projects realized and sold all around the world... I checked, the machine is already in distribution, and it has already similar versions. Look at: http://www.filabot.com/