An inkjet cartridge is a component of an inkjet printer that contains the ink that is deposited onto paper during printing.
Inkjet cartridges can normally be returned to the supplier for reuse or donated to charities that collect them as a revenue stream.
When purchasing new cartridges ask your supplier about returning the empty cartridge for reuse.
Alternatively check to see if your favourite charity collects these for reuse. Irish charities such as https://www.ispca.ie/ provide this service.