We destroy it in an active cement kiln! The Montreal Protocol has a Technology and Economic Assessment Panel outlining approved destruction options[1] and this is one of their approved technologies. It's great for a few reasons:

1. Already operates at negative pressure with a high enough temperature and long enough residence time 2. Alkaline environment neutralizes the HF and HCl that are produced when the refrigerant burns. 3. Already consuming massive amounts of energy so the marginal energy use is negligible. 4. Allows use to use an existing facility instead of building our own -- great for developing countries where building infra is harder (but cement plants are everywhere).

[1] https://ozone.unep.org/sites/default/files/2019-04/TEAP-DecX...