2025 Spring Meeting and 21st Global Congress on Process Safety
(55b) Techno-Economic Evaluation of DAC-HVAC CO2 Capture for Electrochemical Formic Acid Synthesis
Authors
Yusuf Bicer, Hamad Bin Khalifa University
Aliya Banu, Hamad Bin Khalifa University
Namra Mir, Hamad Bin Khalifa University
Abdulkarem I. Amhamed, Hamad Bin Khalifa University
Tareq Al-Ansari, Hamad Bin Khalifa University, Qatar Foundation
Direct Air Capture (DAC) has emerged as a crucial technology for meeting climate mitigation goals, particularly in sectors where point-source CO2 capture is not sufficient to reduce emissions. To meet the Paris Agreement's goal of limiting the global temperature rise, it is not only necessary to reduce current emissions but also to remove previously emitted CO2. However, DAC is still facing significant limitations due to high initial investments, scalability challenges, and substantial operational costs associated with energy consumption. The captured CO2 offers several valuable utilization pathways, one of which is its electrochemical conversion to formic acid, a value-added product with multiple applications. Formic acid can serve as an efficient energy carrier, be directly converted to electricity in formic acid fuel cells and be used in agriculture as a feed preservative. This study presents a comprehensive thermodynamic and economic analysis of an integrated DAC-HVAC system coupled with a CO2 electrochemical reduction (ECR) system for formic acid production. Integrating DAC within HVAC, specifically within the Air Handling Unit (AHU), significantly reduces both the energy consumption and operational costs of the DAC system while also lowering initial investment costs by utilizing existing blowers from the HVAC infrastructure. Leveraging existing HVAC infrastructure for CO2 capture allows for shared resources, lowering the heating and cooling requirements and improving energy efficiency in the DAC process. A thermodynamic model was developed for the DAC-HVAC integration, accounting for regeneration heat, cooling requirements, compression needs, and blower energy requirements associated with CO2 capture. This assessment provides insights into the energy demands of the system and the operational requirements for its integration with the HVAC system. Additionally, modeling of the ECR process involved estimating the flowrates and energy requirements to scale the electrolyzer for the captured CO2. The economic model for the DAC system includes capital expenditures (Capex) for essential components such as vacuum pumps, heat exchangers, adsorbent filters, and compressors, as well as fixed and variable operational expenditures (Opex). The economic analysis for the electrochemical reduction (ECR) system is based on that of a water electrolyzer, utilizing system modeling parameters to align with CO2 electrochemical reduction. Key techno-economic metrics, including levelized cost, net present value (NPV), discounted payback period (DPP), benefit-cost ratio (BCR), internal rate of return (IRR), and break-even unit, were applied to evaluate the feasibility of the integrated DAC-ECR system. Multiple sensitivity analyses were conducted to assess the impact of varying operational variables, commodity prices, and economic parameters on the different economic metrics. Sensitivity factors included faradaic efficiency, current density, formic acid price, electricity price, and discount rate, all of which significantly influence the economics of the integrated system. Results demonstrate that with a DAC levelized cost of 202 $/ton CO2, the cost of formic acid is 0.49 $/kg. These findings suggest that the integrated system can be economically viable with a discounted payback period of 4.1 years and a benefit-cost ratio of 1.19. The positive DPP and BCR indicate that this DAC-ECR system for formic acid synthesis could be a promising pathway for CO2 direct air capture and utilization.
Keywords: DAC, CO2 capture, CO2 utilization, electrochemical conversion, formic acid.
Acknowledgement
The authors acknowledge the support provided by the Hamad Bin Khalifa University and Qatar Environment and Energy Research institute (QEERI) (a member of Qatar Foundation). This publication was made possible by Graduate Sponsorship Research Award (GSRA9-L-1-0430-22001) and NPRP12C-0821-190017 from the Qatar National Research Fund (a member of Qatar Foundation).