How to destroy the recovery information for an Drive Encryption installed system
When you want to secure-erase the drives in your Drive Encryption installed system, remove all users from the system (including those inherited from parent branches in the system tree). This makes the disks inaccessible through normal authentication as there are no longer any users assigned to the system. You must then destroy the recovery information for the system using the option Menu | Systems | System Tree | Systems tab | Actions | Drive Encryption | Destroy All Recovery Information in the ePolicy Orchestrator console. You must also disable the Add local domain user option in the Product Setting Policy. This means that the system can never be recovered.