Carbon dioxide (CO2) capture and sequestration includes a portfolio of technologies that can potentially sequester billions of tonnes of CO2 per year Mineral carbonation (MC) is emerging as a potential CCS technology solution to sequester CO2 from smaller/medium emitters, where geological sequestration is not a viable option In MC processes, CO2 is chemically reacted with calcium- and/or magnesium-containing materials to form stable carbonates This work investigates the current advancement in the proposed MC technologies and the role they can play in decreasing the overall cost of this CO2 sequestration route In situ mineral carbonation is a very promising option in terms of resources available and enhanced security, but the technology is still in its infancy and transport and storage costs are still higher than geological storage in sedimentary basins ($17 instead of $8 per tCO2) Ex situ mineral carbonation has been demonstrated on pilot and demonstration scales However, its application is currently limited by its high costs, which range from $50 to $300 per tCO2 sequestered Energy use, the reaction rate and material handling are the key factors hindering the success of this technology The value of the products seems central to render MC economically viable in the same way as conventional CCS seems profitable only when combined with EOR Large scale projects such as the Skyonic process can help in reducing the knowledge gaps on MC fundamentals and provide accurate costing and data on processes integration and comparison The literature to date indicates that in the coming decades MC can play an important role in decarbonising the power and industrial sector

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A review of mineral carbonation technologies to sequester CO2

Magnesium isotopic compositions of a profile through saprolites developed on a diabase dike from South Carolina have been measured in order to study the behavior of Mg isotopes during continental weathering. As weathering progresses, Mg isotopes are greatly fractionated and are correlated with Mg concentration, clay mineral proportions and density of the saprolites. δ 26 Mg values increase from −0.22 in the unweathered diabase to + 0.65 in the most weathered saprolite. These observations are consistent with the release of light Mg to the hydrosphere and formation of isotopically heavy Mg in the weathered products. The loss of Mg during weathering can be modeled by Rayleigh distillation with an apparent fractionation factor between the saprolite and fluid (α) of 1.00005 to 1.0004, i.e., up to 0.4‰ fractionation in the 26 Mg/ 24 Mg ratio between the saprolite and fluid. The large variation in α value reflects a mineralogical control on Mg isotope fractionation during primary dissolution of Mg-rich minerals and formation of secondary minerals during continental weathering. Like Mg isotopes, Li isotopes in the saprolite profile are also greatly fractionated, with δ 7 Li values ranging from −6.7 down to −20. The large Li isotope fractionation and variation in Li concentration, as well as irregularities in the δ 7 Li profile with depth, however, cannot be explained by Li loss during weathering alone. Instead, Li can be modeled by a two-step process: (1) equilibrium isotope fractionation during continental weathering, which lowered δ 7 Li and Li concentrations and produced a Li concentration gradient in the saprolites like that seen in Mg, and (2) subsequent kinetic isotope fractionation produced by diffusion of Li in the saprolites, possibly across a paleo-water table. The results presented here suggest that continental weathering will shift the Mg isotopic composition of the continental crust to values higher than the mantle value, whereas crustal recycling over the history of the Earth will have no discernible effect on the Mg isotopic composition of the mantle.

Contrasting lithium and magnesium isotope fractionation during continental weathering

The influence of terrigenous particulate material dissolution on ocean chemistry and global element cycles

On the potential of CO2–water–rock interactions for CO2 storage using a modified kinetic model

The reaction of Ca derived from silicate weathering with CO2 in the world’s oceans to form carbonate minerals is a critical step in long-term climate moderation. Ca is delivered to the oceans primarily via rivers, where it is transported either as dissolved species or within suspended material. The relative importance for climate moderation of riverine dissolved Ca vs. suspended Ca transport stems from the total Ca flux and its climate dependence. Data in the literature suggest that, within uncertainty, global riverine dissolved Ca flux is equal to suspended material Ca flux. To determine how these fluxes depend on temperature and rainfall, a 40 yr field study was performed on 4 catchments

Role of river-suspended material in the global carbon cycle

Olivine dissolution rates: A critical review

Growth of the sodiumaluminium-hydroxy carbonate dawsonite (NaAl(OH)2 CO3 ) after charging saline aquifers with CO2 has been assumed in a plethora of numerical simulations at different mineralogies, aqueous solutions, pressures and temperatures. It appears however that dawsonite is less abundant than expected in natural CO2 storage analogues if we take into account the thermodynamic stability alone. We have mapped the thermodynamic stability of dawsonite relative to mineral phases like albite, kaolinite and analcime from 37° to 200°C and performed closed-system batch kinetic simulations using a new kinetic expression including a nucleation term based on classical nucleation theory, and a growth term that was based on BCF growth theory. Using this rate equation, we have performed a sensitivity study on dawsonite growth on mineralogy, temperature, CO2 pressure, nucleation rate and its dependencies on temperature and affinity, and on the dawsonite precipitation rate coefficient. Simulations with dawsonite growth disabled showed that the maximum oversaturation reached for dawsonite for seawater-like solutions never exceeded 3-4 times oversaturation. The positive effect on dawsonite growth of increasing the CO2 pressure was mostly neutralized by higher acidity. Decreasing the precipitation rate coefficient by 5 orders of magnitude had a limited effect on the onset of significant growth, but the amount of dawsonite formed at the end of the 1 000 years simulated time was only 37% below the high-rate case. Reducing the nucleation rates had similar effects leading to postponed dawsonite growth. Finally, based on thermodynamic considerations and numerical simulations, we suggest that the potential of dawsonite growth is limited to a medium-temperature window framed by a high thermodynamic stability relative to competing mineral phases at low temperatures, but with rapidly diminishing nucleation and growth rates at lower temperatures constrained by energy barriers.

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Why is Dawsonite Absent in CO2 Charged Reservoirs

There are three broad types of economic lithium deposit: 1) peralkaline and peraluminous pegmatite deposits and their associated metasomatic rocks; 2) Li-rich hectorite clays derived from volcanic deposits; 3) salar evaporites and geothermal deposits. Spodumene-bearing pegmatites are the most important and easily exploitable Li deposits, typically containing 0.5 Mt Li. Salar deposits hold the largest Li reserves, can reach up to 7 Mt Li, but are more difficult to exploit. Allowing for recycling, the current predicted demand up to the year 2100 is 20 Mt Li; world resources are currently estimated at more than 62 Mt Li. Thus, abundant resources exist, and no long-term shortage is predicted.

Julien Declercq

Papers

Olivine dissolution rates: A critical review

Why is Dawsonite Absent in CO2 Charged Reservoirs

Classification and Characteristics of Natural Lithium Resources

The dissolution rates of dawsonite at pH 0.9 to 5 and temperatures of 22, 60 and 77 C

Experimental determination of rhyolitic glass dissolution rates at 40–200 °C and 2 < pH < 10.1