A FINANCIAL MODEL OF ELECTROCHEMICAL CARBON DIOXIDE REMOVAL FROM SEAWATER FOR GEOLOGICAL SEQUESTRATION
To meet the Intergovernmental Panel on Climate Change’s goal to limit global temperature rise to 1.5°C by the end of the 21st century, carbon dioxide removal (CDR) appears increasingly necessary to stay within their representative concentration pathways. Commercial CDR technologies available today may not scale to the capacity necessary to fill this role, or may be too costly. One of the major drivers for inefficiency in CDR technologies like Bioenergy with Carbon Capture and Storage and Direct Air Carbon Capture and Storage is carbon dioxide’s (CO2) comparative dilute presence in the atmosphere. In seawater however, CO2 is over 100 times more concentrated by volume, and since CO2 maintains an equilibrium between the atmosphere and the ocean, removing it from seawater has the follow-on effect of removing it from the atmosphere. A technology recently developed by the Naval Research Laboratory to synthesize liquid hydrocarbon fuels at sea, extracts CO2 from seawater using continuous electrodeionization to temporarily acidify it, thereby shifting the carbonate equilibrium to favor CO2 such that it can be degassed. This paper proposes modifying their technology to focus on CO2 extraction for the purpose of geological sequestration, rather than fuel synthesis. It uses pro forma cash flow analyses of annual revenues and expenses to estimate the financial viability of the approach across three scenarios representing low, medium and high economic optimism. The levelized cost of CDR calculated through these scenarios were between $179 and $261 per tonne of carbon dioxide (tCO2), which does not reach the carbon pricing corridor proposed by the Carbon Pricing Leadership Coalition (CPLC) of between $50/tCO2 and $100/tCO2. While this suggests the technology is not yet mature enough to compete as an emissions offset, the availability of the 45Q tax credit does make it financially viable under one scenario. With this subsidy providing a financial runway for the technology to mature, the capital and operating expense rates can come down to a level that would support CDR within the CPLC’s carbon price corridor.
Carbon Dioxide Removal, Negative Emissions, Seawater, Electrochemistry