...his negative survey misses a lot of points and is nowhere near comprehensive.
First of all, it is widely recognized that seawater, on a volumetric level contains far more CO2 than does air, moreover in multiple chemical forms, solvated carbon dioxide being one, bicarbonate another, and carbonate as a third, depending on pH. (While the ocean is being acidified, it is still relatively basic.
Dr. Heather Willauer has demonstrated on a pilot scale, using ion selective membranes that let carbon dioxide species pass through the membrane of an electrolytic cell, she can generate hydrogen and carbon dioxide, which, using the FT synthesis to make jet fuel at sea in nuclear powered aircraft carriers, perhaps making this form of war mongering carbon neutral. The cost of jet fuel produced in this way is around $6.00/gallon, close to California gas prices last I was there, and lower than the true cost at some US Naval bases around the world.
Other opportunities present themselves, by using processes already in place, wherever air compression is required. (For various reasons connected with air purification as a side product, I have suggested to my son, Brayton cycles where air is the working fluid on a powerplant. Under these conditions, I propose aqueous solutions of group one or group two metals, preferably radioactive where the carbon would be removed in the compression stage, and continuously precipitated with group 2 oxides (hydroxides in aqueous phases).
It is important that the laws of thermodynamics definitely apply in these conditions, but they can be managed in such away that the carbon dioxide is removed using heat energy that might have been rejected to the environment without being captured as exergy. Most modern nuclear plants are Rankine cycle devices, and thus have roughly 33% to 34% thermodynamic efficiency. This is an outgrowth that original designers of the nuclear plants we now use considered the heat from nuclear reactions to nearly identical to the heat used by coal. (It is also true that materials science was poor in designs that worked other ways: Some Brayton type reactors have operated commercially, however with limited success. The point is that via process intensification we can utilize some of the 67% of wasted exergy for other purposes, a process that I might add, would reduce demand for cooling water.
To my son I preach process intensification via stepped heat transfer to a point which may induce nausea in him.
As for the article. It is not really helpful, since the focus is very narrow. I can assure that the world expert in DAC, Dr. Christopher Jones at Georgia Tech is unlikely to shut his lab on reading this limited overview.
As for where to put the carbon dioxide removed, it can either be recycled, as recommended by Nobel Laureate George Olah 15 years ago, shortly before his death, or be utilized in materials setting.
Anthropogenic Chemical Carbon Cycle for a Sustainable Future George A. Olah, G. K. Surya Prakash, and Alain Goeppert Journal of the American Chemical Society 2011 133 (33), 12881-12898
The thermodynamics of producing these materials once the thermodynamics has been expended to remove from water or air, will involve recovering all of the energy put out when combustion put them there; but again, increasing the thermal efficiency of nuclear plants to around 70% or slightly more, which strikes me as feasible, makes the reduction of carbon dioxide for materials, polymers, and portable fuels where necessary, feasible.
Air capture to greenwash dangerous fossil fuels, like sequestration to greenwash fossil fuels, and like hydrogen to greenwash fossil fuels is a very dubious idea. However, in a world free of fossil fuel energy - an outcome only feasible with nuclear energy - we may be able to slowly restore the atmosphere.
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