Direct Air Capture (DAC) is regarded as an effective method to decrease the concentration of CO2 in the atmosphere and thus alleviate the greenhouse effect. This article conducts a comparative analysis of the CO2 emissions of 12 state-of-the-art DAC technologies. The evaluations consider regional (EU, USA, and China) and temporal (years 2023, 2030, and 2050) energy supply variations. It is found that the CO2 emissions generally decrease over time for all the different regions considered. The best CO2 emission performance is found in Europe, followed by the United States and China. The evaluation also finds that currently a substantial number of DAC technologies could not achieve net-negative emission, especially for China. In 2050, most of the DAC technologies are found to perform significantly better in terms of their negative emission performance. We also found that the utilization of fossil fuels, especially coal, needed to operate the DAC process, substantially hinders its ability to achieve net-negative emission. Electrochemical-based technologies are found to outperform others in all scenarios, especially when powered with renewable electricity. The DAC technologies relying on steambased sorbent regeneration can greatly reduce their CO2 emission when low-carbon energy is used for steam generation. Finally, in all the different scenarios, the DAC technologies incorporating high-temperature calcination regenerations exhibit the worst performance due to the lack of low-emission energies for generating fired heat.