Sequestering CO2 by Mineral Carbonation: Stability against Acid Rain Exposure

• Published in: Environmental science & technology Vol. 44; no. 7; pp. 2735 - 2739
• Main Authors: Allen, Daniel J, Brent, Geoff F
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2010
• Subjects: Applied sciences; Atmospheric pollution; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Energy and the Environment; Exact sciences and technology; External geophysics; General processes of purification and dust removal; Meteorology; Pollution; Prevention and purification methods; Asia; United States; China; Europe; America; Australia; North America; Oceania; USA; China, People's Rep; Sensitivity analysis; Carbon compound; Underground storage; Carbon dioxide; Acid rain; CO2 sequestration; Dissolution; Carbon sequestration; Dynamical climatology; Climate change; Geoengineering; Greenhouse gas; Carbonation; Air pollution; Pollution abatement; Industrial area; Kinetics
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es903212j

Mineral carbonation is a potentially attractive alternative to storage of compressed CO2 in underground repositories, known as geosequestration. Processes for the conversion of basic ores, such as magnesium silicates, to carbonates have been proposed by various researchers, with storage of the carbonate as backfill in the original mine representing a solid carbon sink. The stability of such carbon sinks against acid rain and other sources of strong acids is examined here. It is acknowledged that in the presence of strong acid, carbonates will dissolve and release carbon dioxide. A sensitivity analysis covering annual average rainfall and pH that may be encountered in industrialized areas of the United States, China, Europe, and Australia was conducted to determine maximum CO2 rerelease rates from mineral carbonation carbon sinks. This analysis is based on a worst-case premise that is equivalent to assuming infinitely rapid kinetics of dissolution of the carbonate. The analysis shows that under any likely conditions of pH and rainfall, leakage rates of stored CO2 are negligible. This is illustrated in a hypothetical case study under Australian conditions. It is thus proposed that sequestration by mineral carbonation can be considered to be permanent on practical human time scales. Other possible sources of acid have also been considered.