What is Carbon Mineralisation?
It is a natural process by which Carbon Dioxide (CO2) from the atmosphere reacts with minerals containing calcium or magnesium in solid or dissolved forms in soils, oceans and rocks converting to a carbonate compounds. This process permanently captures CO2 and stores (sequesters) this for many years, effectively removing excess CO2 from the atmosphere and thus mitigating climate change. These phenomena occur organically across various domains, which are briefly elucidated below.
ROCKS
Certain types of rocks, such as calcium and magnesium silicates, can react with atmospheric CO2 over geological timescales. This mineral carbonation process converts CO2 into stable carbonates like calcium carbonate (CaCO3), effectively locking away carbon in solid mineral structures permanently.
OCEANS
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Calcium Carbonate Formation: Dissolved CO2 can react with calcium ions to form calcium carbonate minerals like aragonite and calcite, which can settle to the ocean floor and become part of sediments.
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This process is particularly important in marine environments, as it helps regulate ocean acidity and sequesters carbon over geological timescales
SOIL
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Numerous soil processes naturally capture and sequester CO2. Among these, there is the transformation of organic carbon within plant and microbial biomass into more enduring states, effectively locking away carbon and averting its release into the atmosphere as CO2. A diverse range of organisms, including algae, bacteria, fungi, and plants, play pivotal roles in facilitating carbon mineralization through their metabolic activities.
BUT, in its natural state, mineral carbonation is a slow process, taking thousands to millions of years to significantly reduce the rising CO2 levels from man-made emissions.
Existing technologies, such as Carbon Capture Usage and Storage (CCUS) technologies involve capturing CO2 emissions from industrial processes or power plants and injecting the captured CO2 deep underground into geological formations like depleted oil and gas reservoirs or saline aquifers. The biggest problem with storing CO2 in geological formations and under the sea are both physical and economic. Leakage of CO2 from geological storage reservoirs can lead to global and local risks.
Direct Air Capture (DAC) technologies are designed to capture CO2 directly from the ambient air. Once captured, the CO2 can be processed and mineralised by reacting it with suitable minerals to form stable carbonates.
Some industrial processes, such as cement production, steel manufacturing, and chemical production, release CO2 as a by-product. Various technologies and methods are being developed to capture CO2 emissions from these processes.
Each of these carbon capture technologies have their own disadvantages such as high energy requirements, land space and costs to facilitate. Carbon mineralisation presents significant potential as a carbon removal approach, within a larger suite of carbon removal and climate actions, to help reach global climate goals.