Since the Industrial Revolution, anthropogenic carbon dioxide (CO₂) emissions have grown exponentially, accumulating in the atmosphere and leading to global warming. According to the IPCC (IPCC Special Report, 2018), atmospheric warming should be <2°C to avoid the most serious consequences associated with climate change. This goal may be achieved in part by reducing CO₂ emissions, together with capturing and sequestering CO₂ from point sources. The most mature storage technique is sequestration in deep saline aquifers. In addition, CO₂ can be mineralized and sequestered in solid form by various techniques, i.e., ex-situ, surficial and in situ mineralization. Ex situ and surficial approaches may produce valuable products while mitigating environmental hazards. In-situ mineralization uses ultramafic and mafic geological formations for permanent, solid storage. In addition, the IPCC portfolio that limits warming to <2°C by 2100 includes avoiding CO₂ emissions and removal of CO₂ from air. Regardless of the specific mix of approaches, it will be essential to permanently sequester about 10 billion tons of CO₂ per year by mid-century, and roughly twice that amount each year by 2100. Maximizing the potential of technologies for CO₂ removal from air and CO₂ storage will help to meet global climate goals. The research agenda published by National Academies of Sciences Engineering Medicine (2019) calls for roughly $1 billion over a 10–20 years time period to advance the deployment of CO₂ sequestration in deep sedimentary reservoirs at the GtCO₂/yr scale and develop CO₂ mineralization at the MtCO₂/yr scale. This would lead to a deeper understanding of the reservoir characteristics from the nano- to kilometer scale, some of which may include the distribution of the reaction products, the reaction rate of the minerals, the permeability evolution, the pressure build-up in the reservoir, the large-scale impact of chemicophysical processes leading to clogging or cracking, the effects of potential geochemical contamination, etc. This overview presents the advantages, drawbacks, costs, and CO₂ storage potential of each technique, the current and future projects in this domain, and potential sequestration options in geologic formations around the world.

To avoid dangerous climate change, new technologies must remove billions of tonnes of CO₂ from the atmosphere every year by mid-century. Here we detail a land-based enhanced weathering cycle utilizing magnesite (MgCO₃) feedstock to repeatedly capture CO₂ from the atmosphere. In this process, MgCO₃ is calcined, producing caustic magnesia (MgO) and high-purity CO₂. This MgO is spread over land to carbonate for a year by reacting with atmospheric CO₂. The carbonate minerals are then recollected and re-calcined. The reproduced MgO is spread over land to carbonate again. We show this process could cost approximately $46–159 tCO₂⁻¹ net removed from the atmosphere, considering grid and solar electricity without post-processing costs. This technology may achieve lower costs than projections for more extensively engineered Direct Air Capture methods. It has the scalable potential to remove at least 2–3 GtCO₂ year⁻¹, and may make a meaningful contribution to mitigating climate change.

Mineral carbonation (MC) is a form of carbon capture and storage that reacts CO₂ with alkaline feedstock to securely store CO₂ as solid carbonate minerals. To improve process economics and accelerate commercial deployment, research has increased around product utilization, where markets exist primarily in the construction industry. This review assesses the potential for advancing MC product utilization to decrease CO₂ emissions toward neutral, or even negative, values. First, the literature surrounding the current state and challenges for indirect MC processes is reviewed, indicating that process intensification and scale‐up are important areas for further research. Alkalinity sources available for MC are examined, differentiating between those sourced from industrial processes and mining operations. Investigation of possible end uses of carbonate products reveals that further CO₂ avoidance can be achieved by replacing conventional carbon‐intensive products. Companies that are currently commercializing MC processes are categorized based on the feed used and materials produced. An analysis of company process types indicates that up to 3 GtCO₂ year^–1 could be avoided globally. It is suggested that upcoming commercial efforts should focus on the carbonation of industrial wastes located near CO₂ sources to produce precast concrete blocks. Carbonation of conventional concrete shows the highest potential for CO₂ avoidance, but may face some market resistance. Carbonation of Mg silicates lacks sufficient market demand and requires the development of new high‐value products to overcome the expense of mining and feed preparation. It is suggested that research focus on enhanced understanding of magnesia cement chemistry and the development of flame‐retardant mineral fillers. © 2019 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.