The permanent geological storage of CO 2 has been demonstrated at large scale (up to 1 Mtpa). A number of suitable storage sites have been identified and characterised worldwide. Countries without local geological storage potential that choose to deploy CCS will need to make appropriate arrangements, which will require international agreements. A major hurdle regarding geological CO 2 storage is to develop understanding of the liability associated with abandoning a CO 2 storage site, i.e., "cutand-cap" procedures.