By Dr Paula Carey, Co-founder and Technical Director
Some of the most iconic landscapes of our world are based on carbonate rocks – limestones and dolomites, or chalk. These rock types represent nature’s largest store of carbon dioxide.
Rocks like these have been storing CO2 through mineralisation for over 1000 million years. Carbonation, a form or mineralisation, involves the reaction of metal ions in the form of oxides, hydroxides and silicates, with carbon dioxide to form carbonates. Hence, the process naturally sequesters CO2.
Therefore, controlling and enhancing the natural mineralisation process to permanently capture anthropogenic CO2 emissions, is an intuitive and safe approach to capture carbon. Specifically as, the carbonate molecule is a more stable form of CO2. The transformation of CO2 to CO32- does not require the input of large amounts of energy because it is an exothermic process, i.e. it releases energy. In nature, the reaction takes 1000s to millions of years, because the concentration of CO2 in the atmosphere is relatively low. However, the reaction in its simplest form, CaO + CO2= CaCO3, can take place in minutes at atmospheric temperature and pressure conditions, with CO2 concentrations as low 10% by volume.
Carbon, capture, utilisation and storage (CCUS)
Mineralisation is nature’s way to sequester CO2. By controlling this reaction, CO2 can be captured, utilised and stored permanently in rock formations.
Thermal residues, such as steel slags, cement by-products, ashes from Energy from Waste plants or from the recycling of paper, are sources of calcium ions. In managed conditions, the residues can be used in the carbonation process and can be reacted with CO2to manufacture products for the construction industry. Thereby, permanently capturing the CO2, diverting waste from landfill and manufacturing a product with value. The white cliffs of Dover are not simply iconic landscapes with aesthetic value, they represent the vast potential in controlling the carbonation process to address some of the biggest challenges of our time.