Atmospheric carbon dioxide mineralisation in anthropogenically-derived carbonate deposits

[Geoengineering News]

https://oap.unige.ch/journals/sdk/article/view/1929

Authors: John MacDonald, Charlotte Slaymark, Amanda Stubbs, Marta Kalabová

14 September 2025

https://doi.org/10.57035/journals/sdk.2025.e31.1929

Abstract

Removing carbon dioxide from the atmosphere is important in minimising the impact of anthropogenically-induced climate change. Anthropogenic geomaterials, such as slag and cement, can be utilised in an engineered context for mineralising CO2. However, such anthropogenic geomaterials, typically waste products, were usually deposited on the land surface and left to passively mineralise CO2, resulting in the formation of anthropogenic carbonates. In this study, we document anthropogenic carbonates from a suite of locations across Scotland and Northern England, and use stable carbon and oxygen isotopes to show that they are formed from atmospheric CO2. Carbonates which formed in subaqueous settings recorded δ13C values of -25 to -28 ‰ and δ18O values of -15 to -20 ‰, which indicate rapid precipitation from atmospheric CO2. Subaerially-formed samples recorded slightly higher delta values, indicating partial re-equilibration of the dissolved atmospheric CO2 towards expected equilibrium values with ambient conditions before precipitation. The broad suite of samples from multiple locations across Scotland and Northern England show anthropogenic carbonates are more common than previously realised, which demonstrates their effectiveness in passive drawdown of atmospheric CO2.

Source: SEPM