Maja Bar Rasmussen receives DKK 2,9 million from Independent Research Fund Denmark

"The use of calcium-rich silicates and related waste can become part of the solution to our current climate crisis by actively capturing and storing CO₂ through chemical weathering," says postdoc Maja Bar Rasmussen, who has just received funding from the Independent Research Fund Denmark through their green initiatives.

Calcium-rich plagioclase constitutes up to 90 per cent. of the minerals in the rock type anorthosite and is a common mineral all over the globe and while making up a large proportion of our Earth's lower crust. In addition to calcium, the mineral is rich in aluminum and can be used to produce cement, fiberglass, and other building materials.

In the Nuuk region of Greenland, there are pure anorthosite deposits, which in some cases also contain precious stones, enabling future mining activities here. Waste from these mines is expected to be crushed calcium-rich plagioclase as well as calcium-rich residues from the extraction of aluminum, so-called wollastonite-slag, and these materials theoretically have the potential to capture large amounts of CO₂ from our atmosphere.

"Calcium-rich plagioclase in itself is relatively reactive and has the potential to store 1 g of CO₂ per 6 grams of plagioclase, while wollastonite-slag is significantly more reactive, and thus reacts even faster with the CO₂, in order to precipitate lime-like phases”, Maja explains.

The crushing process is often an obstacle to using minerals to capture CO₂ directly from the atmosphere. The minerals should preferably be very finely crushed, and this in itself requires a lot of energy thus emitting CO₂. But the crushing that already occurs in the mining process helps to make plagioclase and the mining waste attractive to use for CO₂ mitigating measures.

Maja elaborates; "The crushing process which is already associated with the mining work means that this plagioclase does not necessarily have to be further crushed before use, as is now the case with, for example, olivine. In this way, we avoid a CO₂-release that would otherwise be emitted through the crushing, and this plagioclase thus constitutes a more overall green solution when you consider the CO₂ budget for the entire process from extraction to storage use".
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