Seawater electrolysis enables high-quality carbon removal
Abstract
We present the mass balances associated with carbon dioxide (CO2) removal (CDR) using seawater as both the source of reactants, and as the reaction medium via electrolysis. This process involves the application of an electric overpotential that splits water to form H+ and OH– ions, producing acidity and alkalinity, i.e., in addition to gaseous co-products, at the anode and cathode, respectively. The alkalinity that results, i.e., via the “continuous electrolytic pH pump” results in the instantaneous precipitation of calcium carbonate (CaCO3), hydrated magnesium carbonates (e.g., nesquehonite: MgCO3·3H2O, hydromagnesite: Mg5(CO3)4(OH)2·4H2O, etc.), and/or magnesium hydroxide (Mg(OH)2) depending on the CO32– ion-activity in solution. This results in the trapping, and hence durable and permanent (at least ~10,000–100,000 years) immobilization of CO2 that was originally dissolved in water, and that is additionally drawn down from the atmosphere within: a) mineral carbonates, and/or b) as solvated bicarbonate (HCO3–) and carbonate (CO32–) ions (i.e., due to the absorption of atmospheric CO2 into seawater having enhanced alkalinity). Taken together, these actions result in the net removal of ≈4.6 kg of CO2 per m3 of seawater catholyte processed. Overall, this analysis provides direct quantifications of the ability of the process to serve as a means for technological CDR to mitigate the worst effects of accelerating climate change.
Bio Erika La Plante
Erika La Plante is a Co-founder and the Head of Measurement, Reporting, and Verification (MRV) and Environmental Impact Assessment at Equatic. She is also an Assistant Professor of Materials Science and Engineering at the University of California, Davis. She obtained her Ph.D. in Earth and Environmental Sciences with a focus in Geochemistry at the University of Illinois at Chicago and her B.S. in Geology from the University of the Philippines. Erika applies her expertise in the kinetics of low-temperature aqueous processes at mineral-fluid interfaces to address the many research questions in the fields of climate, sustainability, built environment, and energy.
Bio Dante Simonetti
Dante Simonetti is an Associate Professor of Chemical Engineering and is also the Associate Director for Technology Translation in the Institute for Carbon Management at UCLA. The institute’s ongoing projects include SeaChange, an energy-efficient technology that removes carbon dioxide dissolved in seawater; x/44, a method for achieving electrochemical direct air capture; and EPOCH, an electrochemical process for producing portlandite — a limestone and cement replacement — designed to greatly reduce the carbon dioxide emissions associated with cement and concrete production. Dante received B.S. and Ph.D. degrees in chemical engineering from the University of Notre Dame and the University of Wisconsin-Madison, respectively. He joined the UCLA faculty in 2014 after working as an R&D project leader at Honeywell’s UOP. His research interests include reaction chemistry and engineering with a specific focus on reducing the carbon footprint of industrial process and energy generation while also remediating legacy emissions. In addition to his research, Dante has published several peer-reviewed scientific publications and holds several patents in this area of expertise.