The Science: Carbonate Formation
The heart of the Calera process is the formation of novel, metastable calcium and magnesium carbonate and bicarbonate minerals, similar to those found in the skeletons of marine animals and plants, by capturing carbon dioxide from flue gas and converting the gas to stable solid minerals. These novel 'polymorphs' make it possible to produce high reactive cements without calcining the carbonate as is the case with conventional portland cement.
Akin to portland cement and aggregate which derive from mining operations in quarries and subsequent processing, the precise stoichiometry of Calera's cements will vary somewhat by site and will include other trace/minor components. In particular, many trace components will be captured from the flue gas such as sulfur oxides and mercury and will be incorporated into the solid phase as insoluble sulfates and carbonates. After removal from the water and appropriate processing, the solids have value in a number of construction and other applications.
Depending on location and product offering, a Calera proprietary high-efficiency electrochemical process called Alkalinity Based on Low Energy (ABLE) is employed to produce NaOH and other industrial chemicals. This NaOH alkaline source is used in the MAP process to modulate pH to allow mineral carbonation to occur.