Mine Waste Has Great CO2 Storage Potential

A mining engineer and geologist says it’s time to economically value the greenhouse gas-trapping potential of mine waste and start making money from it.

Michael Hitch, mining engineer and geologist at the University of British Columbia, studies the value of mine waste rock for its CO2-sequestration potential (SP). Hitch says mining companies across Canada will be able to offset CO2 emissions with SP rock in the future, and could even be selling emissions credits within 25 years.

Digging, trucking, and processing make mining an energy-intensive industry that emits greenhouse gases. However, mine waste rock that is rich in the mineral magnesium silicate has an inherent ability to react with CO2 and chemically "fix" it in place as magnesium carbonate—an ability that can be greatly enhanced with some processing. Hitch and his colleagues note that this capacity for CO2fixation can be five to ten times greater than total greenhouse gas production from some mine operations.

Two of the team's primary goals are to measure the rate of CO2 fixation in mine waste rock and tailings in a lab setting and to speed up the process. Team members have already observed that CO2 fixation is greatly accelerated in mine tailings, presumably due mainly to the large surface area exposed and available to react after rocks are crushed into small particles.

Hitch is working on this problem alongside researchers Greg Dipple, team lead, and Ulrich Mayer, both of UBC's Department of Earth, Ocean and Atmospheric Sciences, and Gordon Southam, with the University of Western Ontario's Department of Earth Science. Hitch's lab is currently grinding rock and pre-treating the material in order to change its physical and chemical properties. Dipple's group will then examine the material's ability to fix CO2. The collaborating researchers hope to move to field trials in five years.

Another important goal is to use computer modeling to predict the sequestration potential of rocks at specific mining sites. To that end, Hitch is designing a way to use mining planning software to put a dollar value on the amount of SP rock that could be obtained at particular locations.

The safe storage of CO2 in mine waste and tailings for thousands of years is an exciting idea that could refresh the public image of the mining industry. One day, Hitch and his colleagues add, research findings from mining could even be applied to CO2 sequestration projects underground and in marine basins.

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