Hey Lads

is there an easy way to secure erase the free space in OS X El Capitan? It's gone from the new Disk Utility

Use File Vault. Encrypting the whole disk has exactly the same effect as 'secure erase free space' and 'secure empty trash' in terms of security, but without the cost. And it's best practice with mobile devices anyway.

read here:

http://www.macissues.com/2015/10/03/how-to-securely-delete-files-in-os-x-10-11-el-capitan/

You're probably right