The disk in question is disk04 - a 128 GB SSD drive in an external USB enclosure. I booted the Macbook from a X.11 USB install drive and there was an internal SSD drive as well. a simple fdisk ...
If you only have a few hard drives to erase, then a software solution such as DBAN or a hardware solution such as using a hammer to pound 6-inch nails through the drives is workable. But if you go ...