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Sustainability
Big things from small packages
Around the world, mining operators are waking up to the potential value left in their waste products. The process of bioleaching, where microbes are used to extract valuable leftover metals from mine tailings, is a far more environmentally friendly process than the acids that have typically been used in the past. Nicholas Kenny speaks with Ross Orr, president and CEO of BacTech, and Radhakrishnan Mahadevan, professor at the Department of Chemical Engineering and Applied Chemistry, University of Toronto, to learn more about the benefi ts this process can offer the mining industry.
by-product of the mining process, tailings present a significant challenge for the industry – both financially and in terms of sustainability and environmental impact. Usually taking the form of a liquid slurry made of water and fine metal or mineral particles, tailings can also be converted into dry-stack tailings, where the leftover material is compacted into a mound that is then able to be reclaimed by nature. Typically, however, tailings have been stored in anoxic condition under water, as exposure to oxygen can result in chemical reactions that generate acid, capable of poisoning the surrounding environment. Even so, over time these pools will become highly
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acidic, often ranging from 1–3pH. These tailings pools or ponds are based within structures specifically designed to prevent the metals leaching out into the surrounding environment – referred to as ‘tailings dams’. Tailings dams are one of the greatest risk factors in mining – essentially, they’re large bodies of contaminated water held back by concrete and metal, and any potential breach can cause massive damage. Historically, some of the worst modern mining disasters have been due to tailings dam failures, most notably in Brumadinho, Brazil, in January 2019, which resulted in the deaths of 270 people and led Vale, the mining operator responsible, to agree to pay out over
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