Natural gas accounts for 21.3% of the total primary energy supply. In particular, with the shale gas boom, its application has experienced an exponential growth rate. Nevertheless, natural gas has the highest hydrogen to carbon ratio among all hydrocarbons and the dilute (with respect to CO2) exhausts of its combustion pose considerable thermodynamic challenges for carbon capture. Solvent-based carbon capture can potentially mitigate the carbon emissions. Nonetheless, minimizing the penalties associated with the costs of carbon capture requires detailed understanding of the underlying physical and chemical phenomena. The present research exploits a rigorous methodology based on rate-based distributed modelling and statistical associating fluid theory (SAFT). The important characteristics of this modelling approach include abstract formulation in conjunction with high predictability. The present research aims at establishing the performance of a new solvent (an amine-promoted buffer salt, APBS) in comparison to the baseline solvent, i.e., monoethanolamine (MEA). The features of interest include: (i) developing a high fidelity mathematical model of the carbon capture process, (ii) validating the model with pilot plant data, (iii) quantification of the energetic and technical performances of the solvents using key process indicators (KPIs), and (iv) employing optimization programming for further solvent performance improvement.