Hi Catur,
CCS can simply be modeled as a lower CO2 emission factor per unit of fossil fuel burned. As far as I am aware most CCS installations are still in an early pre-commercialized phase of development and most are only capturing a fraction of CO2 generated. The fraction actually stored (i.e. not emitted) is lower still.
Bear in mind that CCS with biomass (BECCS) could potentially have net negative emission factors.
Hope this helps,
Charlie