iPhone secure shredding is not a simple decision because the process needs to manage the small data items inside.
The first step is to find a certified secure destruction company. This company must have three parts to their destruction process for it to be secure.
1st – disassemble the phone and make sure to remove the battery before destruction.
2nd – destroy the iPhone using a grinder/disintegrator that insures the smallest parts are completely destroyed.
3rd – They must utilize an R2 certified recycler that manages the shredded materials in the proper way.