Earth-observation for CO2 sequestration at mine waste sites

Mining generates more than 14 billion tonnes of waste each year, which must be safely stored and managed over decades. In circular-economy frameworks, mine waste is increasingly recognised not only as an environmental liability but also as a potential secondary resource, and industrial-scale valorisation initiatives are already being implemented by major mining companies and specialised start-ups. Using mining waste for CO₂ sequestration presents a particularly promising valorisation approach, as it promotes both the “zero waste” as well as the “net zero CO₂” principles. 

In this contribution, we explore integrated Earth-observation (EO) workflows to support the assessment of CO₂ sequestration potential at mine waste sites through two complementary pathways: (i) passive mineral carbonation, where atmospheric CO₂ is bound through natural weathering of reactive waste materials, and (ii) carbon sequestration through revegetation and improved stewardship of post-mining landscapes. 

Mafic and ultramafic waste materials rich in Mg-Fe-Ca-bearing silicates, including olivine, serpentine, pyroxenes, amphiboles and smectites, exhibit high carbonation potential and occur widely in waste derived from mining of e.g. asbestos, diamonds, Ni-Cr, PGM, and Pb-Zn ores. Despite their abundance in active and legacy waste facilities, identifying and quantifying these minerals at scale remains challenging, as mine waste is intrinsically heterogeneous and existing mine-waste inventories rarely include spatially explicit mineralogical information. Using resolution-enhanced satellite hyperspectral data, we derive spatially continuous maps of reactive mineral assemblages in mine waste deposits through band-ratio analysis, minimum-wavelength mapping, and spectral unmixing based on dedicated mineral libraries. These products support the screening, targeting, and design of mineral-based CO₂ sequestration strategies such as enhanced weathering or ex-situ carbonation. 

In parallel, we monitor revegetation dynamics on mine waste deposits as a proxy for vegetation-based carbon sequestration. Reclamation commonly involves the addition of topsoil or the construction of technosols from waste materials to enable plant growth and soil development. However, revegetation success is often spatially variable due to hydrology, nutrient limitations, toxicity, and surface instability. We apply decomposition and trend analysis to long-term Sentinel-2 and Landsat vegetation-index time series to quantify revegetation trajectories across multiple closed mine sites. This approach reveals fine-scale patterns in rehabilitation success, identifies erosion-affected or delayed-recovery zones and provides objective indicators for optimising reclamation strategies. Where available, LiDAR and hyperspectral data are integrated to characterise vertical vegetation structure and species composition, providing a basis for above-ground biomass estimation, for carbon accounting and crediting assessments.

The presented EO-based monitoring framework, developed within the EU-funded MOSMIN project, enables consistent comparison, prioritisation, and tracking of CO₂ sequestration potential across heterogeneous waste deposits, supporting more sustainable land-use and waste-management strategies.