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

Abstract

High Resolution Image Download MS PowerPoint Slide CO 2 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 CO 3 2– with HCO 3 – in the contactor effluent greatly diminishes the electrolyzer performance and eventually results in a reduced CO 2 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 CO 2 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.