Direct Capture of CO₂ from Ambient Air

Abstract

The increase in the global atmospheric CO concentration resulting from over a century of combustion of fossil fuels has been associated with significant global climate change. With the global population increase driving continued increases in fossil fuel use, humanity's primary reliance on fossil energy for the next several decades is assured. Traditional modes of carbon capture such as precombustion and postcombustion CO capture from large point sources can help slow the rate of increase of the atmospheric CO concentration, but only the direct removal of CO from the air, or "direct air capture" (DAC), can actually reduce the global atmospheric CO concentration. The past decade has seen a steep rise in the use of chemical sorbents that are cycled through sorption and desorption cycles for CO removal from ultradilute gases such as air. This Review provides a historical overview of the field of DAC, along with an exhaustive description of the use of chemical sorbents targeted at this application. Solvents and solid sorbents that interact strongly with CO are described, including basic solvents, supported amine and ammonium materials, and metal-organic frameworks (MOFs), as the primary classes of chemical sorbents. Hypothetical processes for the deployment of such sorbents are discussed, as well as the limited array of technoeconomic analyses published on DAC. Overall, it is concluded that there are many new materials that could play a role in emerging DAC technologies. However, these materials need to be further investigated and developed with a practical sorbent-air contacting process in mind if society is to make rapid progress in deploying DAC as a means of mitigating climate change.

The CO2capturing ability of cellulose dissolved in NaOH(aq) at low temperature

“…Today, there are several materials capable of efficiently capturing CO 2 such as different types of amines and MOFs (metal-organic frameworks). 1 However, many of these systems suffer from being expensive or from being difficult to synthesise, and are to some extent not sustainable since a lot of energy is needed to regenerate CO 2 and to recycle the capturing agent. In this aspect, another interesting system for capturing CO 2 is NaOH (aq).…”

Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system

“…Moreover, in terms of NaOH(aq), the presence of dissolved CO 2 is likely to affect the properties of the solvent system itself by consuming the hydroxide ions in well-known conversions to HCO 3 -and CO 3 2- (Yoo et al 2013) and should as such be taken into account. Aqueous hydroxide sorbents, in itself, have been widely studied for direct capture of CO 2 from air (Sanz-Pérez et al 2016), but the only notation of possible effects of CO 2 on cellulose in an alkaline aqueous system could be found in a work of Pakshver and Kipershlak, dealing with effects of carbonate ions on xanthogenation and dissolution (Pakshver and Kipershlak 1980).…”

The Virtuous CO2 Circle or the Three Cs: Capture, Cache, and Convert

“…The Direct Air Capture (DAC) concept defined as the direct extraction of CO 2 from ambient air was introduced in 1999 [3] and a decade was spent on the viability of this technique as a potential climate change mitigation technology; in the following half decade, there was even increased interest with a large number of publications, but the current technologies do not provide energy/economical efficient separation of CO 2 since concentration in the atmosphere is too low. Thus, DAC techniques, which were effectively reviewed in a recent article by Sanz-Pérez et al [4], are not of particular interest in this paper.…”