they have a shredder machine, that sorts all the metals, the copper, the aluminum, the steel... etc
part of the shredder even gets the change if any was left under the seat or carpet
if there are human remains in the trunk, the machine sense it, and stops.
"Strong Steel Products is a ferrous and non-ferrous metal recycler, operating a "megashredder" plant capable of handling scrap at a rate of 440,000 pounds per hour"
The Strong Steel site is a 9-acre yard and processes in excess of 200,000 tons per year. The operation is purely focused on shredder throughput. Flattened automobiles arrive on trailers. They are fed through the shredder and ferrous material is separated by a magnet.
https://localwiki.org/detroit/Strong_Steel_Products
http://www.fptscrap.com/locations/ftp-strong-steel-products-detroit-michigan/
http://sennebogen-na.com/fit-for-purpose-fpt-chooses-the-right-sennebogen-for-every-job/