An Overview of the Status and Challenges of CO2 Storage in Minerals and Geological Formations

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? 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? 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 GtCO(2)/yr scale and develop CO2 mineralization at the MtCO(2)/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.