1
$\begingroup$

As far as I know, the cheapest non-chemical solution is: grow grass, and burn it. The resulting $\ce{CO2}$ is from the air. But I am interested on chemical industrial solutions now.

As far as I know, the main difficulty of the process is that the ratio of the $\ce{CO2}$ in the air is very low. Thus, extracting it means a large entropy difference.

My layman's intuition is that maybe some substance exists - probably an organic compound - which binds especially strongly to $\ce{CO2}$ and it is easily regenerated. One would pump air through it, and then regenerate it to get the $\ce{CO2}$ back. If such a compound exists, what is it?

The process should be powered by electrical energy only. Thus, solutions such as "buy gas, burn it, and you get much cheaper $\ce{CO2}$" are not acceptable.

On "cheapest" I understand, what is cheapest in industrial size, not in a laboratory? (for example, in a large chemical factory)

$\endgroup$
  • $\begingroup$ Surprisingly, the cheapest solution might be refrigeration. Water vapor will freeze out at $0\ ^\circ\mathrm{C}$ and the next major component of air to freeze out will be carbon dioxide at $-78\ ^\circ\mathrm{C}$. $\endgroup$ – Ben Norris Sep 9 '15 at 17:51
  • $\begingroup$ @BenNorris The ratio of CO2 in air is 0.035%, what is the vapor pressure of -78% CO2? Ok, maybe there is an optimum which depends on the cost of the freezing (and the heat exchanger), where the extracted CO2/$ is maximal. $\endgroup$ – peterh Sep 10 '15 at 22:32
2
$\begingroup$

Your intuition is correct, and such compounds are plenty. The cheapest are probably $\ce{NaOH}$, $\ce{Ca(OH)_2}$ and the like, but these are not easily regenerable. Then there are organic amines, like monoethanolamine, which can do the same in a reversible manner. Indeed, they are used in industry.

$\endgroup$
  • $\begingroup$ This is right. Organic amines are what I've heard the most about for recovering CO2 from gas streams. $\endgroup$ – Sean Doris Sep 9 '15 at 23:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.