What scrap company around town will destroy parts in front of you?

Weird request I know, but I deal with parts from customers all over the country and inspect them. A lot of times they don't want to pay to ship their part back, so I have a large backlog of parts I need to scrap, but I must ensure they are destroyed beyond use before they leave my sight. Think of car seat frames, engine parts, sheet metal components, large steel framework for heavy equipment. What company can do this? Thanks