Hi there, normally with a compatible cartridge the recycling company can check if it's possible to recycle it again and turn it into a new cartridge. If it can, they generally will, but if not they normally crush it down and use the plastics to make other items. Some recycle companies however will not take them back, so it depends on which company they are returned to. You can find more information here:
https://www.tonergiant.co.uk/recycling/
