4. Mineral Carbonation for Carbon Capture and Utilization

The appeal of mineral carbonation (MC) as a process technology for scalable and long-term CO₂ reduction, is that it is a solution that has the sequestration capacity to match the amount of CO₂ emitted from energy generation and industrial activities [1‐3]. Many inorganic materials such as minerals [4, 5], incineration ash [6, 7], concrete [8, 9] and industrial residues [10, 11] are potentially huge sinks for anthropogenic CO₂ emissions. These materials are typically abundant sources of alkaline and alkaline-earth metal oxides, which can react naturally with CO₂ to form inorganic carbonates and bicarbonates. In addition, their products are thermodynamically stable and relatively inert at ambient conditions. On paper, MC should be able to fully sequester all anthropogenic CO₂ emissions, since the abundance of magnesium and calcium atoms on Earth far exceeds the total amount of carbon atoms [12, 13]. However, despite the apparently favorable pre-conditions, we still observe a net accumulation of CO₂ in the atmosphere because the rates of reaction to form (bi)carbonates in nature are too slow compared to the current rate at which CO₂ is being emitted [14, 15]. If left to their own devices, thousands of years are needed to achieve any substantial sequestration of CO₂ [16]. This is clearly not rapid enough to solve the pressing problem of climate change that is already affecting us now. Therefore there is a need to employ mineral carbonation as an artificial method to accelerate the rates of CO₂ sequestration. In this chapter, we will take a look into the chemistry and thermodynamics of mineral carbonation and discuss some of the main obstacles to large scale MC implementation. Additionally, we highlight the types of starting materials from which basic alkaline-earth metal oxides can be obtained and discuss how their abundance and properties affect MC performance. We will also give a short review of current research in the area to develop MC into viable and economic processes, with some focus on the main categories of process designs and their working principles. We will then look at MC from a techno-economic standpoint and assess the opportunities to integrate MC into the existing industrial and environmental landscape. Lastly, we conclude the chapter with a hypothetical scenario of MC deployment in Singapore, an economically developed but land-scarce country under threat by rising sea levels.