CO2 mineralization of kimberlite residues from the Gahcho Kué Diamond Mine, Northwest Territories, Canada

• CO 2 batch leaches, shot-term assessments, and year-long weathering columns were used to predict and quantify CO 2 sequestration. • Gahcho Kué Diamond Mine resides can remove 12 kg CO 2 /t based on labile Ca and Mg. • Year-term monitoring predicted a sequestration rate of 0.63 kg CO 2 /t/yr without enhancements. • An assessment of CO 2 sequestration for 40-days immediately following deposition reveals the total removal 0.86 kg CO 2 /t, as the residues were allowed to dry. • Incorporating enhanced weathering into mine closure would lead to substantial CO 2 removal. Kimberlite residues generated at diamond mines have the potential to substantially reduce net greenhouse gas emissions and contribute towards carbon-neutral mining. As part of the De Beers CarbonVault™, we conducted experiments using fine kimberlite residues from the Gahcho Kué Diamond Mine, Northwest Territories, Canada, to assess the mine's potential for CO 2 sequestration. Batch CO 2 leach tests indicate a CO 2 sequestration potential of 12 kg CO 2 /t based on easily extractable cations from non-carbonate sources. However, an evaluation of the short-term reactivity of the residues post-deposition revealed the ability to sequester 0.86 kg CO 2 /t when residues were allowed to dry through optimal water saturation (30–40 %). Furthermore, year-long weathering columns determined a CO 2 removal rate of 0.63 kg CO 2 /t/yr, primarily through mineral trapping. Extrapolating these rates to current annual residue production and emissions indicates that 7 % of the mine's estimated CO 2 e emissions could be sequestered over the life of mine. These rates are based on optimal storage conditions that keep residues exposed for long periods, which should be a consideration of residue management practices during the operating life of the mine and post closure. Further on-site investigations are necessary to refine rates and account for climatic conditions. Assessments conducted in this study affirm the suitability of Gahcho Kué residues for CO 2 sequestration and present strategies for optimizing this process.