Carbon capture & storage:Carbon Storage in the Earth's Crust
Carbon dioxide reacts with calcium. Tomihahndorf, Creative Commons License
Published: November 9, 2010, 12:00 am
Updated: May 7, 2012, 6:11 pm
This article has been reviewed by the following Topic Editor:
Margaret Swisher
Calcium and magnesium silicon oxides, which are prevalent in certain rocks (like wollastonite, olivine, or serpentine), react spontaneously with CO2 to produce mineral carbonates such as limestone (CaCO3) or magnesium carbonate (MgCO3) in a process known as natural mineral carbonation. Mineral carbonates offer long-term storage because they are stable under ambient temperatures and pressures and can serve as construction materials or as fillers in abandoned mines. To fix a metric ton of CO2 into carbonates requires between 1.6 metric tons and 3.7 metric tons of silicon oxide rock. [1] Nonetheless, Earth’s crust contains more than enough of these silicon oxides to react with all of the CO2 released from combusting the planet’s entire reserves of fossil fuels. Natural mineral carbonation, however, is prohibitively slow.
Accelerating this process to acceptable rates involves mining rocks containing silicon oxides, crushing and grinding them into a powder, and removing impurities (e.g., iron compounds, via magnetic extraction). The silicon oxide powder is then dissolved in a mild acid solution, and CO2 is bubbled through the solution at high temperature and pressure (approximately 185°C and 15 MPa). The reaction forms particles that are smaller in size than the original silicon oxide particles. Finally, the process sieves the fine carbonate particles from the larger silicon oxide particles, disposes of the carbonates, and returns the unreacted silicon oxides to the reaction vessel.
These procedures consume 30% to 50% of the energy generated by a power plant. [1] Together with the 10% to 30% energy penalty for CO2 capture, a power plant equipped CO2 capture and storage (CCS) capability via mineral carbonation expends nearly double the energy for operations than a plant without CCS. As a result, costs for mineral carbonation CCS are several times that of other methods, explaining why mineral carbonation CCS has yet to be implemented on a commercial scale.
Other carbon dioxide storage methods include pumping CO2 into the ocean and burying CO2 in deep geological formations.
This is an excerpt from the book Global Climate Change: Convergence of Disciplines by Dr. Arnold J. Bloom and taken from UCVerse of the University of California.
©2010 Sinauer Associates and UC Regents
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Citation
Arnold J Bloom (Lead Author);Margaret Swisher (Topic Editor) "Carbon Storage in the Earth's Crust". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth November 9, 2010; Last revised Date May 7, 2012; Retrieved May 20, 2013 <http://www.eoearth.org/article/Carbon_Storage_in_the_Earth's_Crust?topic=60464>
The Author
Arnold J. Bloom became a botanist through a circuitous route. Upon receiving an undergraduate degree in Physics from Yale University, he spent several years developing computer models of the spread of air pollution over cities in the USA and Germany. He received a Ph.D. in Biological Sciences from Stanford University, where he also completed a two-semester course in Environmental Legislation at the Law School. He conducted postdoctoral research on the temperature responses of plants at the ... (Full Bio)
Calcium and magnesium silicon oxides, which are prevalent in certain rocks (like wollastonite, olivine, or serpentine), react spontaneously with CO2 to produce mineral carbonates such as limestone (CaCO3) or magnesium carbonate (MgCO3) in a process known as natural mineral carbonation. Mineral carbonates offer long-term storage because they are stable under ambient temperatures and pressures and can serve as construction materials or as fillers in abandoned mines. To fix a metric ton of CO2 into carbonates requires between 1.6 metric tons and 3.7 metric tons of silicon oxide rock. [1] Nonetheless, Earth’s crust contains more than enough of these silicon oxides to react with all of the CO2 released from combusting the planet’s entire reserves of fossil fuels. Natural mineral carbonation, however, is prohibitively slow.
Accelerating this process to acceptable rates involves mining rocks containing silicon oxides, crushing and grinding them into a powder, and removing impurities (e.g., iron compounds, via magnetic extraction). The silicon oxide powder is then dissolved in a mild acid solution, and CO2 is bubbled through the solution at high temperature and pressure (approximately 185°C and 15 MPa). The reaction forms particles that are smaller in size than the original silicon oxide particles. Finally, the process sieves the fine carbonate particles from the larger silicon oxide particles, disposes of the carbonates, and returns the unreacted silicon oxides to the reaction vessel.
These procedures consume 30% to 50% of the energy generated by a power plant. [1] Together with the 10% to 30% energy penalty for CO2 capture, a power plant equipped CO2 capture and storage (CCS) capability via mineral carbonation expends nearly double the energy for operations than a plant without CCS. As a result, costs for mineral carbonation CCS are several times that of other methods, explaining why mineral carbonation CCS has yet to be implemented on a commercial scale.
Other carbon dioxide storage methods include pumping CO2 into the ocean and burying CO2 in deep geological formations.
This is an excerpt from the book Global Climate Change: Convergence of Disciplines by Dr. Arnold J. Bloom and taken from UCVerse of the University of California.
©2010 Sinauer Associates and UC Regents
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