Here, however, we analyze DAC technologies assuming existing energy supply systems, and translated the energy demand values from Table to operational costs for different regions in the world b , using costs and emission intensities for four case study countries and one 'best case' scenario (see Table ). The 'best case' scenario combines the lowest observed energy a It has been stated that the energy requirements of a cryogenic DAC unit are comparable to other DACs only when cryogenic refrigeration units reach efficiencies above 30% (currently around 15%) and heat exchangers operate with a temperature difference between the cold and warm air of less than 3K at the cold end. These operating conditions are limited to arctic regions. Furthermore, these regions are exposed to seasonality, limiting the suitable operation time to 6 to 9 months per year. All these challenges make its scalability to Gt-scale extremely far more difficult than for other processes. Still, RD&D in cryogenic applications is vital, as cryogenic technologies become more competitive in post-combustion capture where CO 2 concentrations are much higher.