-140C only works for CO2-rich streams (> 10%). As the partial pressure of CO2 decreases, you'll need to get asymptotically closer to the melting point of oxygen

-140C only works for CO2-rich streams (> 10%). As the partial pressure of CO2 decreases, you'll need to get asymptotically closer to the melting point of oxygen/nitrogen. You'll also need to increase the pressure, but again that only gets you reasonable temperature gains if the partial pressure of CO2 is >>0mmHg. Currently it is 0.3mmHg @ 400ppm. In short, this is not a viable method for removing CO2 from the atmosphere. For a fun take on some of this see https://wattsupwiththat.com/2009/06/13/results-lab-experiment-regarding-co2-snow-in-antarctica-at-113f-80-5c-not-possible/ https://wattsupwiththat.com/2009/06/13/results-lab-experimen...