Bridging the Gap: A Cost Comparison of Electrochemical and Thermochemical Carbon Capture Technologies
Authors: Ripley Katelyn M. , Brushett Fikile R. 
Published: December 2024

Replacing fossil fuels with renewable energy and removing carbon dioxide (CO2) via carbon capture, utilization, and storage (CCUS) are necessary steps to addressing the current climate crisis and achieving net-zero emissions by 2050.1 While renewable energy is predicted to contribute 62.5% of all net electricity generation in the United States by mid-century, it is also predicted that coal and natural gas plants will need to continue operating in the near-term to meet growing energy demands.2,3 This, coupled with the persistence of hard-to-decarbonize processes such as the manufacturing of steel, iron, cement, and other chemicals, requires point-source capture technologies to mitigate remaining CO2 emissions. State-of-the-art CO2 separation systems are typically based on low efficiency, temperature-swing cycles that exploit the natural affinity of alkanolamines for CO2 at ambient conditions. Recently, electrochemical capture systems have been proposed that may enable CO2 removal from flue gas streams at higher energetic efficiencies while also offering more modular and scalable designs.4 However, direct comparisons between the thermochemical and electrochemical approaches are scant, likely due to the nascency of the latter.

In this presentation, we introduce a process cost model to investigate the conditions that allow 4-stage electrochemical systems (i.e., comprise of an electrochemical reactor, absorption column, and flash tank) to compete economically with an amine scrubbing system. To do this, we first develop an Aspen Plus® model to determine the material and energy flows in a baseline thermochemical system. Second, we develop an in-house model of the electrochemical system to probe the effects of varying molecular properties, operating conditions, reactor configuration, and scale on the overall performance. We then feed the outputs from each of these models to a levelized cost of capture model to directly compare the costs of the electrochemical system to those of the thermochemical baseline, given the same set of assumptions. Finally, we use these models and parameter sweeps to assess the likelihood that electrochemical systems can outperform thermochemical systems on a cost, energy, and indirect emissions basis. Ultimately, this work seeks to lay the foundation for quantitative comparisons between different technologies available for point-source capture applications while also offering a pathway to shift from generalized sensitivity studies towards investigating the viability of promising molecules and electrolytes.

References

International Energy Agency. International Energy Agency (IEA) World Energy Outlook 2022. International Energy Agency 524 (2022).

Annual Energy Outlook 2023. (2023).

International Energy Agency. Energy Technology Perspectives 2020 - Special Report on Carbon Capture Utilisation and Storage. Energy Technology Perspectives 2020 - Special Report on Carbon Capture Utilisation and Storage (2020).

Renfrew, S. E., Starr, D. E. & Strasser, P. Electrochemical Approaches toward CO2 Capture and Concentration. ACS Catal
10, 13058–13074 (2020).