A Comparison of Two Approaches to Direct Air Capture of CO2. [View all]

As it's open sourced, available for anyone to read, I will simply provide a linkto refer to, and make a brief comment on, this paper: On Comparing Packed Beds and Monoliths for CO2 Capture from Air Through Experiments, Theory, and Modeling Valentina Stampi-Bombelli, Alba Storione, Quirin Grossmann, and Marco Mazzotti Industrial & Engineering Chemistry Research 2024 63 (26), 11637-11653.

It's a nice mathematical approach to evaluating the merits of two approaches to two proposed methods of direct air capture.

Direct air capture, like all carbon capture, requires energy, the more dilute the stream, the more energy is required to overcome the entropy of mixing. Thus, in a situation in which CO₂ is being dumped into the air, as with the continuing use of dangerous fossil fuels, it is self defeating by definition. It is a thermodynamic loser.

On the other hand, in a situation in which sustainable clean energy is available - of which there is one, and only one form, nuclear energy - direct air capture might be of help restore the planet from the present conditions of extreme global heating, now observed worldwide. It strikes me as being at the edge of feasibility, albeit only in conditions of process intensification, in which heat is managed in a heat network, flowing from very high temperatures to ambient temperatures. For this to work, the situation would need to be a CCU, "carbon capture and utilization, not CCS, carbon capture and "storage." In this case, CCU, carbon dioxide would be utilized for all material purposes - chemical and structural - now provided by petroleum or coal sources.

This paper refers to two approaches for direct air capture. I'm not truly enamored of either approach, although coupled to Brayton cycles using air as the working fluid (as in a jet engine) with nuclear heat, they might have application.

I personally prefer chemical alkali carbonate formation, again in an air Brayton approach, preferably with radioactive cesium hydroxide, although it is, owing to secular equilibrium effects, unlikely, that we would ever manage to accumulate enough fission products, even in an ideal nuclear powered world, to do anything other than make a small dent in the currently observed disaster of extreme global heating. Rubidium and potassium hydroxides which are not very radioactive, even sodium hydroxide, would also work.

Just a note...