gCCS is the commercial system modelling environment for whole-chain CCS applications that has been developed through the ETI’s CCS System Modelling Took-Kit Project and is now commercially available from PSE. gCCS operates like many standard process flowsheeting tools, but unlike these it contains high-fidelity models of all major CCS operations. In addition, powerful modelling and solution capabilities mean that it can be used for detailed steady-state and dynamic simulation and optimisation across large sections of CCS networks.