Mineral Basalt Sequestration

In situ mineral carbon dioxide sequestration:

In situ mineral carbon dioxide sequestration is a sequestration process in which highly pressurized (super-critical) carbon dioxide (CO2) is pumped into basaltic rock formations in the earth. These basaltic rock formations are rich in mineral silicates that react with CO2 to form mineral carbonates or bicarbonates. This is an exothermic and, thus, thermodynamically favorable reaction that runs deep below ground, sequestering CO2 in a mineral form. (Lackner, 2003).

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This technology is already being implemented and closely monitored in the US and Iceland.

The success of these projects suggests the ability for full industrial implementation within the next 15 years.

Ex Situ Mineral Sequestration:

Ex situ mineral sequestration, is a process similar to the in situ process, but in ex situ, the rock may be transported to a laboratory. Ex situ mineral sequestration is the reaction of carbon dioxide (CO2) with minerals to form stable carbonates above ground. It involves laboratory techniques that catalyze the dissolution of minerals to release cations, which may then react with dissolved CO2 to form geologically stable carbonates. The two main types of rock with which the CO2 interacts are forsterite rock, which is low in magnesium concentration, and serpentine rock, which is high in magnesium concentration. Each of these reacts with the CO2 differently (see equation A) (Guthrie et al, 2002).

equation A) Forsterite Rock: 1/2Mg2SiO4(s) + CO2(g) → MgCO3(s) + 1/2SiO2(s) -95 kJ/mole

Serpentine Rock: 1/3Mg3Si2O5(OH)4(s) + CO2(g) → MgCO3(s) + 2/3SiO2(s) + 2/3H2O(l) -64kJ/mole

Rocks high in magnesium concentration, specifically ultramafic serpentinized rocks, are optimal for mineral sequestration because magnesium is more reactive than other alkaline metals present in rocks (Herzog et al, 2002).

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