To secure erase when that option isn't available in Disk Utility. For example, for SSDs. Boot from another disk or recovery mode. Erase the disk encrypted, with a complex key. Fill the disk with zeros. Erase it again, without encryption or with a different key.
Options to fill with zeros
If it is available, use mkfile, otherwise use dd...
I usually write a blog post about once a week. The latest post can be viewed here: The Social Sciences: I hope you can see where my general frustration with social science comes from! (posted 2024-10-25 at 12:18:53). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2024-08-22 Stirring Up Trouble: Let's just get every view out there and fairly debate them..