Analysis of new strategies integrating bipolar membrane electrodialysis and absorption systems in DAC applications

Abstract

Solvent-based carbon dioxide capture technologies remain among the most promising capture strategies but conventional thermal regeneration methods are hindered by significant drawbacks. In this context, electrochemical regeneration, particularly through the bipolar membrane electrodialysis, offers potential advantages. However, its application is challenged by carbon dioxide bubble formation in the acid compartment, which increases energy requirements. To address this issue, a novel process is proposed in which carbonates in the rich solvent react with weak organic acids to release carbon dioxide while forming acid salts treated in the electrodialysis unit, enabling simultaneous the regeneration of both acid and solvent. To date, comprehensive economic and environmental assessments of such approaches are lacking in the state-of-the-art. This study aims to fill that gap by simulating both the conventional process and alternative pathways based on formic acid and a formic/acetic acid mixtures. Comprehensive material and energy balances are established, alongside detailed evaluations of capital and operating expenditures, and the environmental impact are conducted through life cycle assessment implemented in OpenLCA. Although the alternative processes exhibit higher energy consumption (2314 kWh/tonCO₂ vs 1907 kWh/tonCO₂ with formic acid, and 1943 kWh/tonCO₂ with the acid mixture), the conventional route remains more favorable in terms of both overall cost and environmental impact. Specifically, the total cost and climate change impact of the conventional capture process are estimated to be 480 $/tonCO₂ and –0.9593 kgCO₂_eq/kgCO₂, respectively. On the other hand, the alternative process using formic acid and the mixture acid incur higher costs of 510 $/tonCO₂ and 519 $/tonCO₂ with corresponding environmental impacts of -0.9378 kgCO_2eq/kgCO₂ and 0.9238 kgCO_2eq/kgCO₂, respectively. Further optimization of the conventional process, particularly in mitigating carbon dioxide bubble formation, appears essential to fully exploit its economic and environmental potential.