Hello,
There isn't an easy way to create an Automator workflow to simulate Secure Empty Trash using Terminal, because the srm command requires the full path to be entered for the file each time. Also, it really isn't needed any longer for Macs equipped with SSD or PCIe-based flash storage, as they store data in a different way than traditional hard drives. Because of this, many will recommend simply using FileVault 2 to encrypt the entire disk. Personally, I have never liked or recommended FileVault, as I have seen more problems than it is worth, especially for those who dare to run without Time Machine or another form of data backup. I have worked with many folks that have lost all of their data due to FileVault becoming corrupted, or people forgetting their password/recovery key and being unable to access their data.
-Does the Mac you have running El Capitan have an SSD or PCIe-based flash storage (i.e. Apple SSD)?
-Do you have sensitive enough data to require very strong encryption like FileVault 2?
-Are you using some for of backup for all of your data?
C
