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Mineralization reactions in hard rock mine waste consume carbon dioxide, converting it from a mobile gas into relatively inert solid mineral form. This research may offer a long-term, stable strategy of storing atmospheric CO2. In natural settings, this process stabilizes the concentration of atmospheric CO2 over geological time scales. Carbon mineralization in industrial mine waste is much faster, and if accelerated could consume more CO2 than is emitted during mine operations.
Prof. Greg Dipple and his research team are accelerating carbon mineralization processes. One area of investigation involves increasing the concentration of CO2 supplied to a slurry similar in chemical composition to trailing process water. Results show a 200-fold rate of increase over atmospheric weathering just by increasing the concentration of CO2 in the air passed through the slurry to 10%.
A second approach is using an enzyme, carbonic anhydrase, to catalyze the hydration of aqueous CO2 to a form that is more easily mineralized. Finally, both methods will be combined – higher concentrations of CO2 will be used with the enzyme.
The research is also comparing major Canadian industrial emitters of CO2 with bedrock occurrences and mine sites for mafic to ultramafic rocks to access proximities of sources and sinks. Results show there are significant opportunities for CO2 storage in ultramafic rock-hosted mines and bedrock occurrences outside of the sedimentary basins that are optimal for more conventional carbon capture and storage.
$120,000 / 2 years
The technology can be transported to countries with mining operations. There is potential to securely store CO2 from mining operations for thousands to millions of years.
This research has applications for the mining industry. Carbon could be sequestered in tailings and waste rock. Some large mines could operate as net carbon sinks, turning their mine waste into a resource by absorbing the carbon dioxide emissions of other industries.
None at this time.
Harrison, A.L., Power, I.M., Dipple, G.M. (2012) Accelerated Carbonation of Brucite in Mine Tailings for Carbon Sequestration. Environ. Sci. Technol. July 6, 2012 (web) DOI:10.1021/es3012854
Power, I.M., Wilson, S.A., Small, D.P., Dipple, G.M., Wan W., and Southam, G. (2011) Microbially mediated mineral carbonation: Roles of phototrophy and heterotrophy. Environmental Science & Technology. 45: 9061-9068.
Bea, S.A., Wilson, K.U., Mayer, G.M., Dipple,Power, I.M., & Gamazo, P. (2011) Reactive transport modeling of natural carbon sequestration in ultra-mafic mine tailings, accepted for publication. Vadose Zone Journal. October 2011.
Some mine waste has an inherent but untapped capacity to absorb and trap the greenhouse gas carbon dioxide. In mine waste rock and tailings that are rich in magnesium silicate minerals, carbon fixation capacity is much larger than total greenhouse gas production from mine operations. The carbon mineralization project will develop processes for capturing carbon dioxide in mine wastes and fixing the carbon within mineral precipitates for safe long-term storage.
The project will examine the chemical reactions by which carbon dioxide is trapped and fixed in mineral form through controlled laboratory experiments so that they can be accelerated for enhanced carbon dioxide uptake. The role of biologically mediated reactions in carbon fixation, and the potential for microbially mediated acceleration of carbon uptake will be examined experimentally. The experiments will also be used to calibrate a geochemical model for predicting rates of carbon mineralization at a wide range of reaction conditions and for subsurface reaction in existing mine waste accumulations.
Experimental work has demonstrated that uptake of CO2 into solution is rate limiting for carbon mineralization in mine tailings. Gas streams ranging in composition from atmospheric (~04%) to 100% CO2 were sparged into alkaline slurries containing brucite, a tailings mineral. Brucite was completely replaced by the magnesium carbonate mineral, nesquehonite, within 75, 12 and 7 hours with 10%, 50% and 10% CO2 gas respectively. Experimental carbon mineralization rates were accelerated by a factor of up to 2200, and exceed that required to carbonate all the brucite produced annually at the Mount Keith Nickel Mine (MKM) in Western Australia.
Major Canadian industrial emitters of CO2 were compared with bedrock occurrences and mine sites for mafic to ultramafic rocks to access proximities of sources and sinks. Results show there are significant opportunities for CO2 storage in ultramafic rock-hosted mines and bedrock occurrences outside of the sedimentary basis that are optimal for more conventional carbon capture and storage.
Figure 1 shows a comparison of the range of passive annual carbonation rates at Diavik Diamond Mine, Northwest Territories, Canada (Wilson et al 2011), Clinton Creek chrysotile mine, Yukon Territory, Canada (Wilson et al 2009), and the Mount Keith Nickel Mine (MKM), Western Australia (Wilson 2009) with annual greenhouse gas emissions at various mine sites, total sequestration capacity, and potential annual carbonation rates at MKM via accelerated brucite carbonation.