Gama et al. (2024): Process Operability Analysis of Membrane-Based Direct Air Capture for Low-Purity CO2 Production

Vitor Gama, Beatriz Dantas, Oishi Sanyal, Fernando V. Lima IN: ACS Engineering Au, https://doi.org/10.1021/acsengineeringau.3c00069

This study investigates the feasibility of using membranes as direct air capture (DAC) technology to extract CO2 from atmospheric air to produce low-purity CO2. In this work, a two-stage hollow fiber membrane module process is designed and modeled using the AVEVA Process Simulation platform to produce a low-purity (≈5%) CO2 permeate stream. Such low-purity CO2 streams could have several possible applications such as algae growth, catalytic oxidation, and enhanced oil recovery. An operability analysis is performed by mapping a feasible range of input parameters, which include membrane surface area and membrane performance metrics, to an output set, which consists of CO2 purity, recovery, and net energy consumption.


Robertson et al. (2024): Polymer Sorbent Design for the Direct Air Capture of CO2

Mark Robertson, Jin Qian, Zhe Qiang IN: ACS Applied Polymer Materials, https://doi.org/10.1021/acsapm.3c03199

Here, direct air capture (DAC) represents an essential need for reducing CO2 concentration in the atmosphere to mitigate the negative consequences of greenhouse effects, involving systems that can reversibly adsorb and release CO2, in which polymers have played an integral role. This work provides insights into the development of polymer sorbents for DAC of CO2, specifically from the perspective of material design principles. The authors discuss how physical properties and chemical identities of amine-containing polymers can impact their ability to uptake CO2, as well as be efficiently regenerated. 


Ünal et al. (2024): The nexus between direct air capture technology and CO2 emissions in the transport sector

Emre Ünal, Alexander Ryota Keeley, Nezir Köse, Andrew Chapman, Shunsuke Managi IN: Applied Energy, 363, 123112, https://doi.org/10.1016/j.apenergy.2024.123112

British Columbia provides a substantial chance to examine emissions that were produced after the DAC actions were put into place in 2015. In this study, the difference-in-differences methodology is employed for the very first time to compare the emissions that are produced by the transport sectors in British Columbia with those emitted by other provinces in Canada. The role that GDP and population play in the release of emissions is also taken into consideration in this paper. Based on the research results, it can be observed that the implementation of DAC initiatives has yielded notable effects. 


Nature – Scott-Buechler et al. (2024): Communities conditionally support deployment of direct air capture for carbon dioxide removal in the United States

Celina Scott-Buechler, Bruce Cain, Khalid Osman, Nicole M. Ardoin, Catherine Fraser, Grace Adcox, Emily Polk, Robert B. Jackson IN: Communications Earth & Environment, 5, https://doi.org/10.1038/s43247-024-01334-6

Direct air capture has gained traction as a method for carbon dioxide removal. How and whether direct air capture can be deployed requires securing social license to operate, and increasingly demands environmental justice and just transition principles. Here the authors use a nationally representative survey to evaluate public perceptions of direct air capture, paired with focus groups to assess community perceptions across four communities in the United States: Houston, Texas; Monaca, Pennsylvania; Bakersfield, California; and Rock Springs, Wyoming. 


Zhu et al. (2024): Confinement Effects on Moisture-Swing Direct Air Capture

Yaguang Zhu, Austin Booth, Kelsey B. Hatzell IN: Environmental Science & Technology Letters, https://doi.org/10.1021/acs.estlett.3c00712

Direct air capture technologies are energy intensive and often utilize pressure and temperature swings for sorbent regeneration. An alternative approach, called moisture-swing direct air capture, relies on the hydrolysis of a confined anion to produce hydroxide anions. These hydroxide anions are active sites for CO2 capture. Here, the authors examine how confinement affects moisture-swing CO2 capture and regeneration mechanisms.


PhD-thesis: Concentrating Alkalinity for Direct Air Capture of Carbon Dioxide: Using Osmotic Pressure for Concentration and Separation

Anatoly Rinberg, Harvard University, https://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37377926

First, the author proposes a new approach for removing atmospheric CO2, the alkalinity concentration swing (ACS), driven by concentrating and diluting aqueous alkaline solution, which increases and decreases the partial pressure of CO2 of the solution, respectively. Second, he improves on the ACS process by introducing a selectivity step, which separates bicarbonate ions from carbonate ions. A theoretical investigation reveals that bicarbonate-enrichment allows for reaching higher cycle capacity, higher CO2 partial pressure, and improved absorption rates. Third, nanofiltration is experimentally studied, and confirmed as a mechanism to enrich bicarbonate ions, reaching bicarbonate-carbonate selectivity factors above 30. Fourth, he experimentally demonstrates the ability to use reverse osmosis, a membrane-based separation process driven by applied pressure, as a method for concentrating alkalinity.


Wenger & D’Alessandro (2024): Improving the Sustainability of Electrochemical Direct Air Capture in a 3D Printed Redox Flow Cell

Samuel R. Wenger & Deanna M. D’Alessandro IN: ACS Sustainable Chemistry & Engineering https://doi.org/10.1021/acssuschemeng.3c07866

To enable the scale-up of electrochemical direct air capture (DAC), it is critical to enhance the sustainability of the process by maximizing efficiency and optimizing for targeted durability. Currently, many of the organic molecules reportedly used for electrochemical CO2 capture suffer from degradation upon extended redox cycling in the presence of oxygen, which generates chemical waste. Furthermore, off-the-shelf electrochemical flow cells─an integral piece of equipment for redox flow processes─cost thousands of dollars to procure. In this work, we addressed these challenges by exploring the DAC cyclability of five organic molecules.


Béres et al. (2024): Assessing the feasibility of CO2 removal strategies in achieving climate-neutral power systems: Insights from biomass, CO2 capture, and direct air capture in Europe

Rebeka Béres, Martin Junginger, Machteld van den Broek IN: Advances in Applied Energy, 14, 100166, https://doi.org/10.1016/j.adapen.2024.100166

In this study the European power system in 2050 is modelled at an hourly resolution in the cost-minimization PLEXOS modelling platform. Three climate-neutral scenarios with targets of 0, -1, and -3.9 Mt CO2/year (which agree with varying levels of climate justice) are assessed for different biomass levels, and CCS availability. Findings under baseline assumptions reveal that in a climate-neutral power system with biomass and CCS options, it is cost-effective to complement variable renewable energy with a mix of combined cycle natural gas turbines (CCNGT) for flexibility and BECCS as base load to compensate for the CO2 emissions from natural gas and additional carbon removal in the net-negative scenarios.


Garrido et al. (2023): Implementing vanadium peroxides as direct air carbon capture materials

Eduard Garrido Ribó, Zhiwei Mao, Jacob S. Hirschi, Taylor Linsday, Karlie Bach, Eric D. Walter, Casey R. Simons, Tim J. Zuehlsdorff, May Nyman IN: Chemical Science, DOI: 10.1039/D3SC05381D

Here the authors explore metastable early d0 transition metal peroxide molecules that undergo stabilization via multiple routes, including DAC. Specifically here, they describe via experiment and computation the mechanistic conversion of A3V(O2)4 (tetraperoxovanadate, A = K, Rb, Cs) to first a monocarbonate VO(O2)2(CO3)3−, and ultimately HKCO3 plus KVO4. Single crystal X-ray structures of rubidium and cesium tetraperoxovanadate are reported here for the first time, likely prior-challenged by instability. Infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), 51V solid state NMR (nuclear magnetic resonance), tandem thermogravimetry-mass spectrometry (TGA-MS) along with calculations (DFT, density functional theory) all converge on mechanisms of CO2 capture and release that involve the vanadium centre, despite the end product of a 300 days study being bicarbonate and metavanadate. 


Cameli et al (2024): Conceptual Process Design and Technoeconomic Analysis of an e-Methanol Plant with Direct Air-Captured CO2 and Electrolytic H2

Fabio Cameli, Evangelos Delikonstantis, Afroditi Kourou, Victor Rosa, Kevin M. Van Geem, Georgios D. Stefanidis IN: Energy Fuels, https://doi.org/10.1021/acs.energyfuels.3c04147

CO2-based methanol synthesis routes solely based on renewable electricity have been proposed. However, the production route via direct air-captured (DAC) CO2 and green H2 from water electrolysis (WE) is not industrially available, and in-depth feasibility studies are needed to determine its viability. By designing a 50 kt y–1 e-MeOH production plant based on DAC-CO2 and electrolytic H2, the authors assess the plant’s performance and economic feasibility against the state-of-the-art industrial manufacturing based on natural gas steam reforming. Absorption-based DAC accounts for the highest capital expenditure (CAPEX) of the plant, whereas the proton-exchange membrane WE drives electricity consumption.