Techno-economic analysis of indirect carbonation processes for carbon sequestration using mining waste†

Abstract

Carbon mineralization offers the potential to durably store gigatonne-scale CO₂ emissions, with mining waste representing an especially promising feedstock due to its relatively small particle size, global availability, and opportunities for decarbonizing the mining sector. Despite significant research into the scale and potential of this technology, there remains a lack of techno-economic analyses (TEAs) that comprehensively capture the full-process costs of indirect carbonation using a pH-swing approach. This approach enables both CO₂ storage in carbonates, potentially usable to decarbonize concrete, and the extraction of critical minerals, incorporating the costs and revenues of coupling these processes. To address this gap, we developed a Class IV TEA tailored to estimate the costs and life cycle assessment (LCA) of combining critical mineral extraction and carbon mineralization in mining wastes. The model evaluates scenarios for various waste types (i.e.., legacy asbestos waste, aggregate quarry tailings, platinum group metal tailings) under different extraction conditions (acid type, temperature, strength) and carbonation parameters. Additionally, sensitivity analyses explore the effects of reactor design, internal acid–base recycling, and other factors on process costs and carbon efficiency. Our findings show carbon efficiencies of up to 95%, depending on process design. Acid–base recycling is critical for cost-effective and carbon-negative operations: without recycling, process costs exceed $3000 per tCO₂ and yield a carbon efficiency of −280%, while internal acid regeneration reduces costs to $500–800 per tCO₂ with carbon efficiencies ranging from 41–72%. Process costs vary by waste type and process conditions, ranging from $800–1800 per tCO₂ (assuming 10% reagent makeup), with the carbonate precipitation step contributing 34–78% of total costs. The TEA highlights that acid–base recycling is essential for scaling the pH-swing process on mine tailings and should be a research priority to enable gigatonne-scale CO₂ storage by mid-century. Additionally, selectively recovering critical minerals in wastes where magnesium and calcium are not exclusively leached could significantly offset capital costs.