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

Department of Geosciences and Natural Resource Management

The money will be used to investigate whether calcium-rich silicates can be part of the solution to storing excess atmospheric CO2.

Maja Bar Rasmussen will investigate the potential for using anorthosite to capture CO2 using laboratory-based experiments with anorthosite and materials related to the extraction of aluminum from anorthosite mines in Greenland. Photo: Kent Pørksen.

"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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