I’m not sure I understand what you mean. Sure, assuming that Hawking radiation exists, you could use a black hole to convert mass to electromagnetic radiation (although the emission power would be exceptioally low for any macroscopic black hole).
Strictly speaking, you’re completely destroying the mass, but in the process gaining equivalent energy from nowhere. Of course, it balances out in the end.
Strictly speaking, you’re completely destroying the mass, but in the process gaining equivalent energy from nowhere. Of course, it balances out in the end.