Closing the Loop: Unexamined Performance Trade-Offs of Integrating Direct Air Capture with (Bi)carbonate Electrolysis

Hussain M Almajed; Recep Kas; Paige Brimley; Allison M Crow; Ana Somoza-Tornos; Bri-Mathias Hodge; Thomas E Burdyny; Wilson A Smith

doi:10.1021/acsenergylett.4c00807

Closing the Loop: Unexamined Performance Trade-Offs of Integrating Direct Air Capture with (Bi)carbonate Electrolysis

ACS Energy Lett. 2024 May 1;9(5):2472-2483. doi: 10.1021/acsenergylett.4c00807. eCollection 2024 May 10.

Authors

Hussain M Almajed^{1

2}, Recep Kas³, Paige Brimley^{1

2}, Allison M Crow^{1

2

3}, Ana Somoza-Tornos⁴, Bri-Mathias Hodge^{2

3

5

6}, Thomas E Burdyny⁴, Wilson A Smith^{1

2

3}

Affiliations

¹ Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.
² Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80309, United States.
³ National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
⁴ Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
⁵ Department of Electrical, Computer and Energy Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.
⁶ Department of Applied Mathematics, University of Colorado Boulder, Boulder, Colorado 80309, United States.

Abstract

CO₂ from carbonate-based capture solutions requires a substantial energy input. Replacing this step with (bi)carbonate electrolysis has been commonly proposed as an efficient alternative that coproduces CO/syngas. Here, we assess the feasibility of directly integrating air contactors with (bi)carbonate electrolyzers by leveraging process, multiphysics, microkinetic, and technoeconomic models. We show that the copresence of CO₃^2- with HCO₃^- in the contactor effluent greatly diminishes the electrolyzer performance and eventually results in a reduced CO₂ capture fraction to ≤1%. Additionally, we estimate suitable effluents for (bi)carbonate electrolysis to require 5-14 times larger contactors than conventionally needed contactors, leading to unfavorable process economics. Notably, we show that the regeneration of the capture solvent inside (bi)carbonate electrolyzers is insufficient for CO₂ recapture. Thus, we suggest process modifications that would allow this route to be operationally feasible. Overall, this work sheds light on the practical operation of integrated direct air capture with (bi)carbonate electrolysis.