The Potential of Industrial Mine Waste for Gigatonne-Scale CO₂ Removal: Insights from DHT GeoSustainability Inc.
Introduction
Rising atmospheric carbon dioxide (CO₂) levels are a primary driver of climate change, necessitating innovative solutions for carbon capture and storage (CCS). Industrial mine waste, particularly from mafic, ultramafic, and alkaline rocks, presents a vast and underutilized resource for gigatonne-scale CO₂ removal. Recent research by DHT GeoSustainability Inc. highlights the potential of historical mine waste to sequester up to 21 gigatonnes of CO₂. This approach addresses both climate change and transforms mining byproducts into valuable assets for sustainable carbon management.
The Opportunity of Mine Waste in Carbon Capture
Mining operations generate significant quantities of waste rock and tailings rich in minerals that are chemically reactive with CO₂. Mafic and ultramafic rocks, commonly associated with nickel, platinum group elements, and chromite mining, are abundant in magnesium and calcium silicates. Alkaline mine waste, derived from materials like limestone and dolomite, also exhibits high reactivity with CO₂. These minerals naturally undergo weathering processes, reacting with CO₂ to form stable carbonate minerals and effectively locking away carbon for geological timescales.
Mafic and Ultramafic Rocks
Mafic and ultramafic mine wastes are particularly promising for CO₂ sequestration due to their high magnesium and calcium content. When exposed to air and water, these silicate minerals react with CO₂ to form magnesium carbonate (magnesite) and calcium carbonate (calcite). Recent research by others estimate that historical mafic and ultramafic mine waste could sequester approximately 6.5 gigatonnes of CO₂ through this mineral carbonation process. This substantial potential underscores the significance of these waste materials in global carbon management strategies.
Alkaline Mine Waste
Alkaline mine waste offers even greater potential for CO₂ removal. Materials derived from limestone, dolomite, and certain industrial byproducts react rapidly with atmospheric CO₂ to form stable carbonates. Due to their fast reaction kinetics, these materials can sequester CO₂ more quickly than other natural processes. Current research suggests projects that utilizie historical alkaline waste could enable the removal of up to 21 gigatonnes of CO₂ from the atmosphere. This represents a significant contribution to mitigating climate change impacts.
The Science of Mineral Carbonation
Mineral carbonation is a geochemical process where CO₂ reacts with reactive minerals to form stable carbonate compounds. CO₂ dissolves in water to form carbonic acid (H₂CO₃), which then reacts with minerals like olivine and serpentine, releasing cations such as Mg²⁺ and Ca²⁺. These cations combine with carbonate ions to precipitate carbonate minerals, effectively trapping CO₂ in a solid, stable form for millennia. This natural process can be accelerated in mine waste environments due to increased mineral surface area and exposure.
Advantages of Mineral Carbonation
A key advantage of mineral carbonation is its permanence; the carbon is securely locked into solid minerals, minimizing the risk of re-release into the atmosphere. Unlike biological sequestration methods, mineral carbonation is not susceptible to disturbances such as wildfires or land-use changes. Additionally, the abundance of suitable mine waste materials makes this approach cost-effective and scalable. The exothermic nature of the reactions also means that the process can be energy-efficient.
Role of Geochemical Modeling in Carbon Sequestration
DHT employs advanced geochemical modeling to predict the efficiency and capacity of CO₂ sequestration in various mine wastes. These models simulate mineral carbonation reactions under different environmental conditions, optimizing processes for maximum carbon capture. Accurate modeling is essential for scaling up operations and ensuring the economic viability of CCS projects. By understanding the kinetics and thermodynamics of the reactions, DHT can tailor strategies to specific mine sites.
Leveraging Mine Waste for Carbon Sequestration
Operating within existing mining footprints, DHT's approach minimizes environmental disruption while capitalizing on readily available resources. By leveraging historical mine waste, the company provides a pathway for gigatonne-scale CO₂ removal with minimal additional land use. This strategy aligns with sustainable development goals by repurposing waste materials that would otherwise pose environmental hazards.
Operating on Existing Footprints
Integrating CCS processes into current mine waste management practices avoids the need for new infrastructure and land disturbance. Tailings facilities and waste rock piles already expose reactive minerals to the atmosphere, offering ideal sites for enhanced mineral carbonation. This approach reduces implementation costs and leverages existing operational knowledge within the mining industry.
Scalability and Environmental Impact
The vast quantities of reactive mine waste globally make this approach highly scalable. By converting waste materials into carbon sinks, mining operations can significantly reduce their carbon footprint and contribute to global CO₂ reduction targets. This method also addresses environmental concerns associated with mine waste, such as acid rock drainage, by stabilizing hazardous minerals through carbonation.
The potential for gigatonne-scale CO₂ removal through the mineral carbonation of industrial mine waste presents a promising avenue for combating climate change. DHT GeoSustainability Inc.'s research underscores the viability of transforming mining byproducts into a sustainable tool for carbon management. By harnessing natural geochemical processes and operating within existing mining infrastructures, this approach offers a cost-effective, scalable, and environmentally responsible solution to reduce atmospheric CO₂ levels.
