In conversation with Dr Paula Carey
1. What is the carbonation process?
Carbonation takes place naturally with the formation of limestone or the weathering of basic and ultrabasic igneous rocks. However, in nature this takes thousands of years because of the low concentration of CO2 in the atmosphere. The reaction involves metal ions in the form of oxides, hydroxides and silicates, with carbon dioxide to form carbonates.
2. Why is carbonation important in relation to Net Zero targets?
It is significant as the carbonation process permanently captures CO2 as carbonate. This is the case either from the atmosphere – as part of the natural carbon cycle – or from flue gas emissions of CO2. The latter includes CO2 from some of the most energy intensive industries that also produce residues, which react to the CO2. This means that using carbonation can help address two problems 1) CO2 emissions and 2) alkaline wastes going to landfill.
Carbonation can help meet Net Zero targets as it is a feasible carbon capture, utilisation, and storage (CCUS) solution.
3. What potential does carbonation have for CCUS technologies?
One of the important things about carbonation is that it is a low energy process. In actual fact, it is an exothermic reaction and so produces energy, rather than using it.
This is different to many other CCU technologies, which require large amounts of energy to push the CO2 into a higher energy state in chemicals and fuels. Because of this, Accelerated Carbonation Technology (ACT) is economically viable. Not only does it not require energy input, but the carbonation process also allows for the treatment of alkaline wastes with CO2 and manufacturing products.
There are giga tonnes of reactive residues around the world and therefore, there is the potential to capture over 500 mega tonnes of CO2 if the technology was implemented globally. Additionally,carbonation is the only form of utilisation that permanently captures the CO2 rather than letting it back into the atmosphere when the fuel is burnt or as the plastics degrade.
4. What role does CCUS play in the decarbonisation of industry?
It is widely accepted that, due to the extent of the decarbonisation that needs to take place to reach Net Zero, multiple solutions will be required. Carbon capture and storage presents one solution however, because heavy industries produce so much CO2, this is an extremely expensive process. The CO2 emissions need to be captured, purified and transported for geological storage. Additionally, this requires the development of necessary infrastructure.
Therefore, although geological storage is one solution, it should not be seen as a silver bullet. Utilising the captured CO2, that is to say through CCUS technologies, to manufacture products is a way to offset these costs. This can be in the form of fuels, plastics or carbonated products. In the case of ACT, this is taken even further, as the costs of landfill are also avoided.