## 3 Results and Discussion
### KPIs: Energy Consumption and Cost of DAC Systems
Economic analysis is carried out with the evaluation of CAPEX and OPEX for each process with different sorbents. Table S3 shows the analysis of capital costs for different adsorbent beds, starting from the evaluation of equipment (adsorber and fan) costs. For the adsorber, the mass of the shell of carbon steel is calculated according to the relation provided by [PERSON] and [PERSON] [107] and equal to 1200 kg. For the fan, the impeller diameter is evaluated to be 0.38 m [108]. Overall, CAPEX is determined by the sum of working capital and fixed capital investment, working capital assumed to be 15% of total capital investment. Results show that for all sorbents, annualized capital costs are 11500 USD/year, while the CAPEX cost breakdown is reported in Figure S2. Specific capital costs are lower for amine-functionalized sorbents: 214 USD/tonneCO2 for the cellulose-based sorbent and 221 USD/tonneCO2 for the silica gel-based sorbent. For MIL-101, MOF-177, and MOF-5, specific capital costs are, respectively, 446 USD/tonneCO2, 447 USD/tonneCO2, and 479 USD/tonneCO2. The evaluation of operating costs is reported in Table S4 while the OPEX breakdown cost in reported in Figures S3-S7. Here, the OPEX is different for each adsorbent bed, and higher operating costs are required for physiospents due to higher costs for utilities, especially cooling water (since a greater amount of cooling water is required to remove the greater overall amount of heat that is required for the regeneration step) and thermal energy. Specific OPEX for SI-AEATPMS and APDES-NFC-FD are, respectively 7.756 USD/tonneCO2 and 5.537 USD/tonneCO2. On the other hand, for MIL-101, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sorbent** & **MIL-101** & **MOF-177** & **MOF-5** & **SI-AEATPMS** & **APDES-NFC-FD** \\ \hline Regeneration mode & TSA & TSA & TSA & TSA \\ Regeneration temperature (K) & \(3.73\times 10^{2}\) & \(3.73\times 10^{2}\) & \(3.73\times 10^{2}\) & \(3.83\times 10^{2}\) & \(3.73\times 10^{2}\) \\ Pressure drop (Pa) & \(1.94\times 10^{3}\) & \(1.94\times 10^{3}\) & \(1.94\times 10^{3}\) & \(7.34\times 10^{2}\) & \(6.36\times 10^{2}\) \\ Electrical energy (kWhel/tonneCO2) & \(1.54\times 10^{3}\) & \(1.35\times 10^{3}\) & \(1.52\times 10^{3}\) & \(3.57\times 10^{2}\) & \(2.99\times 10^{2}\) \\ Working capacity (mol/kg) & \(3.5\times 10^{-4}\) & \(3.9\times 10^{-4}\) & \(8.4\times 10^{-4}\) & \(3.67\times 10^{-1}\) & \(7.71\times 10^{-1}\) \\ Regeneration energy (kWhth/tonneCO2) & \(1.07\times 10^{6}\) & \(1.3\times 10^{6}\) & \(4.94\times 10^{5}\) & \(1.88\times 10^{3}\) & \(1.4\times 10^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Energy consumptions for different adsorbent beds. MOF-177, and MOF-5 these costs are 66,100 USD/tonneCO\({}_{2}\), 38,900 USD/tonneCO\({}_{2}\), and 15,800 USD/tonneCO\({}_{2}\). Overall, total costs are 751 USD/tonneCO\({}_{2}\) for the cellulose-based sorbent, 977 USD/tonneCO\({}_{2}\) for the silica gel-based sorbent, 66,600 USD/tonneCO\({}_{2}\) for the MIL-101 sorbent, 39,400 USD/tonneCO\({}_{2}\) for the MOF-177 sorbent, and 16,300 USD/tonneCO\({}_{2}\) for the MOF-5 sorbent. The economic analysis suggests that operating costs have the highest influence on total costs for all investigated systems, especially for those using MOFs. In particular, the contribution of OPEX and CAPEX on total costs is, respectively, 72% and 28% for the system using the cellulose-based sorbent, 77% and 23% for the system using the silica gel-based sorbent, 99% and 1% for the process using MIL-101 and MOF-177, and 97% and 3% for the system using MOF-5. For the capture system using the SI-AEATPMS sorbent, the cost of cooling water is significant, suggesting the use of free air for the cooling stage in order to reduce costs. Another significant contribution is from the maintenance and repairs cost, which is evaluated as 2% of the fixed capital investment. This cost could be reduced by using equipment with another material that with a lower carbon content could allow lower costs.