Electrochemical CO2 Capture and Storage With Hydrogen Generation

Electrochemical 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. CaCO(3) is dissolved in the presence of the highly acidic anolyte of a saline water electrolysis cell, forming Ca(OH)(2) and H(2)CO(3) (or H(2)O and CO(2)). By maintaining a pH between 6 and 9 in the resulting solution, subsequent hydroxide reactions with CO(2) primarily produce dissolved calcium bicarbonate, Ca(HCO(3))(2). Thus, for each mole of CaCO(3) split, there can be a net capture of up to 1 mole of CO(2). The resulting dissolved Ca(HCO(3))(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 CO(2) mitigated. Other potential co-benefits of the approach include: i) production of significantly carbon-negative H(2) 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 H(2), 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 CO(2) absorption and Ca(HCO(3))(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 CO(2) mitigation and "super green" hydrogen generation. (C) 2008 Elsevier Ltd. All rights reserved.