Shredding 'by hand'

I haven't had the change to test my extrusion machine, but it's clear I need some way to turn my failed prints into small pieces. Since I don't want to spend a lot of money before I know if this is something that makes sense, I'm trying out some different things to shred the plastic 'by hand'.

My main trick now is to heat it with a tosti-iron, and then cut it to pieces with cuttin plyers. Not fast, but effective.