Sequestering CO₂ by Mineral Carbonation: Stability against Acid Rain Exposure

Abstract

Mineral carbonation is a potentially attractive alternative to storage of compressed CO(2) 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 CO(2) 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 CO(2) 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.

A Novel Method for CO2 Sequestration via Indirect Carbonation of Coal Fly Ash

“…1 This method is highlighted by its huge storage capacity and considered to be a long-term option for CO 2 storage. 2−4 The raw materials used for mineral sequestration can be natural Ca/Mg silicate ores or industrial alkaline residues.…”

Mineralization of Carbon Dioxide: A Literature Review

“…The ex situ methodologies using mafic/ultramafic rock types and/or industrial byproducts as the cation source must also deal with the sheer feed volume, and the increased product volume, as carbonation results in a weight and volume gain. An uncertain factor that needs further investigation is the ultimate environmental stability of the formed carbonate material [222,223]. While large surface deposits of silicate minerals occur worldwide, greatly exceeding available quantities of fossil fuels [13], the scale of mining operations could be problematic.…”

Engineered Mammalian Carbonic Anhydrases for CO2 Capture

“…The sequestered gas can be either pressurized to a liquid or chemically converted to a stable compound, which can then be stored underground or in the ocean (18,34). This potential shortcoming can be superseded if the carbonates are stored in geographic regions that would be better suited for geosequestration such as in serpentinite or wollastonite deposits (for magnesite and calcite, respectively) or in an area where the average annual rainfall is low (35). This potential shortcoming can be superseded if the carbonates are stored in geographic regions that would be better suited for geosequestration such as in serpentinite or wollastonite deposits (for magnesite and calcite, respectively) or in an area where the average annual rainfall is low (35).…”