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New Tech Treats Mine Waste With CO2

November 8th, 2016 by

Mine waste in a tailings pond

Mine waste ©Paulrommer | Dreamstime.com

Mining operations not only create dangerous waste products, the emissions from their on-site power plants pump large amounts of CO2 and other greenhouse gasses into the air. One company in Canada is developing a promising new technology that will combat both types of pollution at the same time, and save money while doing it.

This new method of cleaning up mine waste captures CO2 from the smokestacks of the mine’s power plant, then uses it in a special process to neutralize acidic mine waste. The idea originated with Strategic Metals CEO Doug Eaton, while he was working on solutions to both problems separately.

power-stationFossil fuel power plants are the only solution to the electrical needs of remote mining operations, especially in Canada’s Yukon Territory where Strategic Metals operates. Eaton was working on an economically viable way to reduce greenhouse gasses from these power plants, in order to meet environmental safety standards for a new mine. At the same time, he wanted to find some way to safely treat the toxic mine waste that accumulates at any mining operation.

He hit upon the idea that the solution to one problem may also be able to solve the other. Mine waste is usually full of ferric compounds, notably iron sulfides. He reasoned that carbon dioxide could theoretically be used to turn those compounds into stable iron carbonate (siderite).  Not only is the smokestack CO2 sequestered into the siderite, but acid rock damage to the ground is reduced. The siderite itself can then be safely shoveled back into worked-out mines, or possibly processed to extract the iron ore. As another bonus, the process produces sulfuric acid, which can be sold for industrial use.

The idea seemed to be a win/win/win situation. The task now was get it to work. This led Easton to the University of British Columbia, where he met professor Lee Groat. Groat agreed that the idea had potential, and set about bringing it to reality. He tried several ways to force CO2 to bond with the sulfides from mine waste and precipitate siderite, but the solution proved elusive.

"Stand back, I'm doing SCIENCE"

“Stand back, I’m doing SCIENCE”

There is a saying that most big scientific discoveries are not met with shouts of “Eureka!”, but rather by someone saying “Hmm, that’s funny…” Professor Groat found the answer to his problem the same way. He noticed that when one particular thermocouple was used to measure the temperature of the test solution, the process succeeded in precipitating iron carbonate. However, when that thermocouple wasn’t used, the experiment failed. Electricity was the answer. That thermocouple had a short, and was introducing an electric current to the solution. They had proven that the processed worked.

The final hurdle is to scale the process up to a commercial scale. A pilot program at Strategic’s Britannia mine in the Yukon is slated to begin next year to test the commercial viability of the mine waste mitigation and carbon sequestration process. A spinoff company, named Terra CO2 Technologies, has been formed by Strategic to pursue improvements in the efficiency of the process. Advances have been impressive enough that Terra is a semifinalist in the $20 million Carbon Xprize competition.

The company is also working to adapt the process for use at coal-fired power plants as a profitable method of CO2 scrubbing. Another field where the process would be useful is the mitigation of mine waste at abandoned/closed mines. A small reclamation facility could be built on site that would use its own CO2 emissions to process hazardous tailings piles and waste ponds into stable compounds.

Who knew that a heavy industry like mining could reduce its environmental impact so much?



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