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Advances in Mineral Carbonation of CO2

A recently-completed techno-economic investigation commissioned by TCGR’s Carbon Dioxide Capture and Conversion (CO2CC) Program

See report TofC here (as PDF)

You no doubt know that there is an unmet need for the development of technology that can remove current and future carbon dioxide (CO2) from the atmosphere in order to avoid a 2°C increase of the planet’s temperature by 2100. It is in this vein that TCGR’s most recent Carbon Dioxide Capture and Conversion (CO2CC) Program techno-economic report, “Advances in Mineral Carbonation of CO2 was created for organizations in the energy/fuels, petrochemical/chemical and allied industries.

One promising mechanism for carbon capture and sequestration (CCS) technology is mineral carbonation. Mineral carbonation refers to the reaction of CO2 with alkaline divalent cations (i.e., Ca2+, Mg2+) to produce stable carbonate minerals at atmospheric conditions. This reaction occurs in accordance with acid-base chemistry, where the carbonate product represents the neutralization of the acidic CO2 with the basic alkaline metal oxides and hydroxides. Although the mineral carbonation process occurs on geological timescales, in mineral carbonation technology, CO2 is captured and reacted with minerals (i.e., serpentine, olivine, wollastonite) or industrial byproducts (i.e., steel slag, bottom ash) that contain alkalinity (typically calcium or magnesium). This reaction forms stable carbonate materials that provide storage capacity for the CO2 on geological timescales, essentially sequestering the CO2.

The volume of reservoirs worldwide demonstrates insight into the potential effectiveness of storing atmospheric CO2 by means of mineral carbonation. While the total mass of CO2 currently in the atmosphere totals around 800 Gt, 39,000,000 Gt of CO2 are present in carbonate rocks (i.e., limestone, chalk, marble) in the Earth’s crust. To better understand the prospects of the mineral carbonation process, the process reaction kinetics and thermodynamics, sources of alkalinity and alkalinity-containing minerals, ex situ (both direct and indirect) and in situ carbonation strategies, and the evolution of mineral carbonation technology are discussed in this new report.

For the mineral carbonation reaction, there currently exist two main sources of alkalinity: natural minerals and industrial byproducts. Each of these sources provide unique opportunities to industrialize the scale of mineral carbonation. Within the carbonation reactions, there are two main areas of distinction: ex situ and in situ. Ex situ carbonation involves taking the chosen mineral away from its source to carbonate, generally to an area where CO2 is produced. These reactions occur in the presence of pressurized CO2, as the alkalinity is typically brought to the gas source. This indicates that the pressurized CO2 reactions are the main area to increase the feasibility of the ex situ carbonation.

In addition to mining waste, the more widely accepted definition of in situ mineral carbonation is the injection of CO2 underground (where alkaline-minerals can react with the higher amount of CO2 to form carbonates). This form of mineral carbonation is similar to geological storage, where CO2 is injected into deep geologic formations.

Figure 1. Production of industrial alkalinity and CO2. Source: Kirchofer A, et al. (2013).
Assessing the Potential of Mineral Carbonation with Industrial Alkalinity Sources in the US. Energy Procedia.

A selection of industrial approaches is representative:

  • Carbon8 Systems has developed “Accelerated Carbonation Technology (ACT)” that they use to treat steel slag, MSWI ashes, and other waste products with captured CO2. This gas-solid mineral carbonation forms Carbon8 Aggregate (C8A) which makes for a low-emission alternative for aggregate concrete blocks.
  • CarbonCure sources their waste CO2 from local industrial gas suppliers who collect emissions from industrial polluters.
  • Solidia Technologies develops their own low-emission cement and concrete, directly carbonating the calcium in their cement with CO2 during the manufacturing process.
  • Calera has been able to use raw captured flue gas directly to aqueously carbonate calcium hydroxide, forming a calcium carbonate powder.
  • Carbicrete has entirely forgone the use of cement in producing their concrete. Instead they use steel slag as the primary binder while injecting CO2 into their wet concrete to carbonate the steel slag.

Other companies have found additional uses outside of purely concrete applications:

  • Cambridge Carbon Capture uses their own “CO2LOC technology” with two separate stages. The resulting MgCO3 product is a valuable building material that can then be sold and used for construction while permanently capturing the incorporated CO2.
  • Carbon Capture Machine dissolves their CO2 in an aqueous mineral carbonation reaction with dilute alkalinity. The generated carbonate solution is reacted with calcium and magnesium ion waste brines to precipitate CaCO3. These carbon negative products can then be sold as feedstocks to other industries.

For carbonation processes to sufficiently reduce global CO2 emissions, they must increase in scale enough to counter the immense emissions from current industrial processes. To do this, the mineral carbonation process will need to be made economically viable and several aspects of the overall process will need to be improved and optimized.

TCGR’s CO2CC Program is an industrial consortium dedicated to seeking, reporting and developing win-win economic solutions to CO2 capture and conversion focused on practical ways to generate both savings and lower costs to expand CO2 utilization options and enhance bottom line profitability! The program has been working since 2010 to identify solutions, with numerous resources already in place.

Don’t be left behind! Align with leading industrial CO2CC Program member-companies like BASF, Dow, Equinor, ExxonMobil, Petrobras, Reliance and Total, among others, in the CO2 conversion space by joining the CO2CC Program today. This is the only way to get TCGR’s in-depth and unparalleled report, Advances in Mineral Carbonation of CO2.

More information about this and other services of the CO2CC Program can be seen at http://www.catalystgrp.com/php/tcgr_co2cc.php.
Call +1-215-628-4447 or e-mail John J. Murphy at jmurphy@catalystgrp.com, and we’ll be happy to discuss these and other interesting membership benefits.

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The Catalyst Group Resources (TCGR), a member of The Catalyst Group, is dedicated to monitoring and analyzing technical and commercial developments in catalysis as they apply to the global refining, petrochemical, fine/specialty chemical, pharmaceutical, polymer/elastomer and environmental industries.