Mineral carbonation

Mineral carbonation is the term for naturally-occurring chemical reactions that bind atmospheric carbon dioxide (CO₂) with minerals.  In nature these processes typically occur at very slow rates, taking hundreds or even thousands of years. Our research aims to develop technologies to rapidly accelerate these processes to permanently store more CO₂ in less time, as benign, inert minerals. 

Our research will focus on technology both in-situ and ex-situ. Ex-situ mineral carbonation refers to processes that take place at the Earth’s surface (involving mine-waste materials for example), whereas in-situ processes take place underground. We estimate that our research will rapidly accelerate naturally occurring mineral carbonation and enhance its capacity for CO₂ storage.

What we know

Rock weathering has played a key role in the global carbon cycle for millions of years, through chemical reactions that convert atmospheric CO₂ to minerals and soluble ions. This confirms the potential of these processes for secure carbon removal from the atmosphere. If enhanced these processes have the potential to securely remove large amounts of carbon.  

Suitable minerals for mineral carbonation exist within the earth but by-products from mining, already crushed and accessible above ground also show promise. Mine waste and tailings are a legacy issue for the mining industry. Utilising these waste materials for carbon storage could help solve this legacy issue. Many of these rocks are ultramafic, or high in magnesium, which increases their utility in the carbonation process.

Key research challenges

Our main priority is to develop the means to accelerate mineral carbonation processes to a matter of weeks or a few years. Each carbon mineralisation pathway (ex-situ and in-situ) also has its own challenges. Our research will seek to:

• Better identify and understand the rocks and minerals with the greatest mineral carbonation potential.
• Enhance our understanding of the micro-structure of the mineral-water interface during mineral carbonation reactions, the reaction mechanisms and the factors that influence mineral dissolution-precipitation reactions. Further, we need to determine the thermodynamic and kinetic properties during these reactions in order to establish reliable geochemical modelling.
• Identify the most effective ex-situ processes and the unit operations required to achieve them; examine the carbon storage potential/capacity using various types of tailings or mine waste materials.
• For ex-situ mine waste and tailings it is important to ensure accelerated carbonation processes do not themselves create tailings and a further legacy problem.
• Develop modelling of the mineral carbonation process in order to predict the possible site and time where the carbonation process occurs. This allows us to assess the speed at which it is occurring and the potential for different kinds of rocks and tailings.
• Define the best strategy to inject CO₂ fluids into in-situ rocks to minimize the operational risks such as injectivity loss due to mineralisation in near injection wellbore.
• Assess several risks including reservoir engineering, rock geomechanics, and CO₂ containment due to the changes of mineral volume as a result of mineral carbonation reactions.

If successful, what might this program achieve?

Success will see this technology utilised by a range of high-emissions industries in order to draw down atmospheric carbon dioxide and store it at much higher rates than is currently possible. The true potential of this technology will be realised through integration with other carbon dioxide removal technologies being developed through the CarbonLock Future Science Platform.