Where do broken iPhone screens go after Apple replaces them?

Was just wondering where do broken iPhone screens go after Apple replaces them

Our business buys them back from non-official iPhone repair centers but it seems Apple stores don't have the authority (for good cause) to sell to a company like ours. Regardless, I was wondering what Apple might do with them as I'm sure it's tens of thousands a week if they added up from all of their locations in just the US alone.