Secure disposal of 3D prints
Big batches need you to be time efficient - or use a method that uses little work. So my suggestions are mainly needing oversight. Keep a fire extinguisher and safety gear handy though!
Melting together
Most filaments are melting at or around 200 °C.
I recently got rid of my box of (PLA) waste material by putting them on a tray and melting them together in a standard kitchen oven at 200 °C for about 1-2 hours. The resulting plate of plastic destroyed all structure that could be identified. This plate can be then broken up or recycled without the risk to disclose any company secrets.
I suggest to use a baking paper under the filament to be molten or a teflon coated tray, as the filament will be REALLY sticky to a blank metal surface.
About 4 liters of broken prints resulted in approximately a 5x450x300 mm sheet. If you make sure that no filament can touch the heating elements, you can get rid of quite a lot of material in each batch.
Don't do this with ABS and don't contaminate your food trays with plastic rests - use specially marked ones that are for disposal of prints only.
Green destruction
If you want to be green when destroying prints: a box solar cooker with a glass lid easily runs at 200 °C, is decently cheap and runs all day on just a couple seconds of adjusting every hour or so. You have to set it up in an access restricted area, but as long as the sun shines, it runs pretty much for free. Just make sure to put the prints to be destroyed onto some kind of non-combustible carriers, like tinfoil or aluminium trays.
ABS in Acetone
If you use ABS, exposing it to acetone fumes for a short time (seconds to half a minute will smooth the surface. Give it some minutes can destroy the structure into a batch of plastic waste without heat that hardens as the acetone evaporates again, though complex structures might need as much as an hour. Dunking ABS into acetone results in pure chemical waste, that is just a waste of acetone.
To save acetone and a way to the chemical waste disposal, try this:
Put a batch of several prints into a large, airtight box that isn't made from ABS. Pour some acetone on a tray and add a paper towel to generate a consistent acetone atmosphere in the box. Make sure to keep the tray on the floor of the box but in a way so no print will fall into it. This should dispose of the prints by merging them into a huge lump within about an hour.
Do this outside &amp; keep fire away.