(524d) Equatic: The Development of a Seawater-Based Atmospheric Carbon Removal and Hydrogen Co-Production Platform

The trapping of carbon dioxide (CO₂) as an aqueous (bi)carbonate ion (e.g., HCO₃^–, CO₃^2–) or as a mineral solid is attractive because of favorable thermodynamics, and the durability and permanence of storage. Here, I will describe an approach to rapidly precipitate Ca- and Mg- carbonates and hydroxides from seawater to achieve large-scale, cost-effective CO₂ removal. This Equatic process electrolytically forces mineral carbonate precipitation – from seawater – thereby consuming CO₂ that is dissolved in seawater by locking it within carbonate minerals, and simultaneously producing alkaline mineral hydroxides that when (re)dissolved in seawater enable the drawdown of atmospheric CO₂. Specifically, 1 mol of CO2 is captured per 2 mol of OH^– produced by the formation of 1 mol CaCO₃. In addition, only 1.2 mol of OH^− are required per 1 mol CO₂ stored as dissolved HCO₃^– and CO₃^2– ions. This is because when dissolved into seawater, every mol of Mg(OH)2 leads to the absorption of up to ~1.7 mol of CO₂. In addition, I will describe the translational design, fabrication, commissioning and operations of pilot plants in Singapore and Los Angeles which demonstrate a net energy intensity (NEI) of ~1-to-1.5 MWh per tonne of atmospheric CO₂ removal.