For low security applications I just (carefully) break them by hand (careful: ballistic polycarbonate, so cover your eyes). Shredding would be good, but it would take an expensive shredder. Sudden thermal stress (liquid nitrogen, etc) might be good enough to delaminate, leaving clear disks behind. ----- Forwarded message from Peter Gutmann <pgut001@cs.auckland.ac.nz> -----