Mark Stevenson

“you’ve done a bit of chemistry, you might recall that sodium carbonate reacts with CO2 to create sodium bicarbonate (baking soda). Well, in Klaus’s machines there is a hanging gallery of strands of a ‘sorbent’ resin – impregnated sodium carbonate – which react with the CO2 in the air flowing over them, the captured CO2 helping to create baking soda. Capturing CO2, though, is only one half of the job. Somehow you’ve got to get the CO2 off the sorbent if you want the apparatus to be reusable and therefore cost-effective. Restocking the whole shebang with a new supply of sorbent resin makes things prohibitively expensive and energy hungry. This is where Lackner’s resin comes into its own, by doing something that even Klaus admits is counterintuitive. In the presence of water the resin changes its affinity for CO2, shedding its recently collected bounty. The ‘collection’ reaction takes a reverse step. Sodium bicarbonate becomes sodium carbonate. What this means is that if Klaus pumps water vapour into his machines, CO2 from the sorbent will ‘fall off’ the resin, allowing the whole apparatus to be reused. Condensing that vapour allows the captured CO2 to bubble out the top, in the same way CO2 bubbles rise to the top of champagne. There’s a kind of sweet poetry to one greenhouse gas (water vapour) collecting another (CO2). After all, one of the problems with CO2 in the atmosphere is that it encourages more water vapour into the air, thereby amplifying the warming effect. Here, thanks to the chemistry of Lackner’s sorbent, the opposite is happening. Water vapour is being used as part of a process to take CO2 out of the air.”
― Mark Stevenson, An Optimist's Tour of the Future