Russia-based Norilsk Nickel (Nornickel)—the world’s largest nickel producer—is studying the potential for mining tailings to capture and store CO2. The dompany is also working to develop a methodology to take stock of carbon units captured this way.
In 2021, Nornickel extracted 41.2 mt of ore. Ore mining and concentration results in waste rock, or tailings—fine-grained rock (less than 0.4 mm) that looks like sand. As a waste, tailings are stored in designated storage facilities called tailing dams.
Silica and magnesium oxide contained in waste rock can absorb carbon dioxide during weathering (long-term exposure to air). By reacting with water and air, carbon dioxide is bound with minerals and metals, which are present in these types of rock, resulting in the formation of carbonates. This process is called mineralization. The outcome is that carbon dioxide from the atmosphere is transformed into secondary minerals in the form of carbonates.
Under Nornickel’s environmental strategy, the group’s Scope 1 and Scope 2 emissions (direct emissions linked to production and indirect emissions associated with power consumption) are expected to go down by 25% by 2028 to reach 7.7 mtpa, compared to 10.3 mtpa currently.
Given the company’s vast production volumes, potential CO2 absorption by waste rock might well reach several million tonnes per year.
Nornickel’s Technology Innovation Department started working to give an estimate of this potential. The Department, together with teams at the group’s facilities, collected 200 samples to study the processes of natural and engineered mineralization of waste rock.
After that, a research institute will analyze the mineral and chemical composition of the samples to assess the content of captured carbon dioxide.
Together with scientists, Nornickel is also working on engineered mineralization of tailings. This technology can be used at the company’s production sites: as an example, flue gases of heat and power plants or process gases of smelting furnaces, containing among other things carbon dioxide, can be bubbled through the process slurry. This will help to increase the potential for GHG absorption considerably, the company says.