Electrochemical CO2 capture and storage with hydrogen generation

AbstractElectrochemical splitting of calcium carbonate (e.g., as contained in inexpensive and abund ant minerals such as limestone) is proposed as a novel method of forming hydroxide solutions that can absorb, neutralize, and store carbon dioxide from the air or from waste streams. CaCO3 is dissolved in the presence of the highly acidic anolyte of a saline water electrolysis cell, forming Ca(OH)2 and H2CO3 (or H2O and CO2). By maintaining a pH between 6 and 9 in the resulting solution, subsequent hydroxide reactions with CO2 primarily produce dissolved calcium bicarbonate, Ca(HCO3)2. Thus, for each mole of CaCO3 split, there can be a net capture of up to 1 mole of CO2. The resulting dissolved Ca(HCO3)2 can be diluted and stored in the ocean, or in reservoirs on land or underground. Net process cost is estimated to be <$100/tonne CO2 mitigated.Other potential co-benefits of the approach include: i) production of significantly carbon-negative H2 if renewable - or nuclear - derived electricity is used as the power source, ii) the option of locally producing electricity and freshwater via fuel cell oxidation of the H2, iii) direct neutralization of ongoing ocean acidification if the Ca(OH)2 generated is added to seawater, iv) preservation or enhancement of otherwise threatened marine shellfish and coral populations, via CO2 absorption and Ca(HCO3)2 formation in or addition to the marine environment, and v) safe ut ilization of the ocean’s vast carbon storage and energy production potentials for CO2 mitigation and “super green” hydrogen generation