Automation of User Accounts for iRecruitment and Self-Service

We are a manufactuing facility and not all of our production workers have internal email accounts.  We are rolling out irecruitment and HR self-service.  We don't want to manually create user accounts for everyone if we don't have to -- I'm look to see if anyone know of an automated way to create / manage accounts, or possibly if anyone has used the registration process to create accounts by employee ID (instead of the default email)