Sustainability The site of the
Brumadinho tailings dam disaster that led to the deaths of 270 people on 25 January 2019.
social and corporate governance (ESG) forward, the industry is slowly waking up to the solution’s benefits. That’s not to say that bioleaching is an entirely new process, of course – the first bioleaching plant was built in the mid-1980s. Today, there are over 20 such plants worldwide, three of which were developed by BacTech under licencing deals. Now, however, the company is making moves into owning and operating its own plants, currently in the process of developing a facility in Tenguel – Ponce Enriquez, Ecuador, which is focused on processing high-grade concentrates and eventually tailings. The plant will be small enough to start with – capable of handling 50t per day (tpd), compared with a 2,000tpd operation in Kazakhstan run by Goldfields. The BacTech site will later be expanded to 200tpd in a second phase. “Ultimately, it’s very simple – we’re using nature’s ability to do what it would normally do, but sped up from around 20 years to six days,” says Orr. “You might have to sacrifice a little profitability to do it cleaner than what you’ve been doing in the past, but that’s the way it is.”
Maximising microbial efficiency While BacTech’s bioleaching solution makes use of naturally occurring bacteria, other groups, particularly in academia, have begun looking at modifying microbes to improve their bioleaching capabilities. One such group is based out of the University of Toronto, which has been collaborating with a group of mining firms to bioleaching processes for use in recovering nickel. While their focus in on enhancing bacteria through adaption evolution, the team of researchers are also developing similar process using genetically engineered bacteria. Led by Radhakrishnan Mahadevan, a professor in the Department of Chemical Engineering and Applied
World Mining Frontiers /
www.nsenergybusiness.com
Chemistry at the University of Toronto, this research partnership with the Faculty of Applied Science and Engineering includes leading mining companies like Vale, Glencore, Metso-Outotec, MIRARCO, Yakum Consulting and, of course, BacTech. The research partnership’s work all began with an investigation by Mahadevan and Vladimiros Papangelakis, professor of hydrometallurgy at the University of Toronto, looking into how biology could be applied to the mining industry – with particular focus on retrieving nickel from pyrrhotite tailings, an iron sulphide mineral. Attempting to characterise the microbial population found in pyrrhotite tailings, they went out to a tailings pond and retrieved the bacteria directly. From there, they began to enhance the microbes through adaptive evolution, gradually increasing the percentage of tailings solids present in the environments of samples that continued to grow well. Over time, this created new strains of microbes that were more effective at carrying out key chemical reactions.
“Once we were reasonably happy with the extent of growth, we looked at the microbes that were there present,” Mahadevan notes. “And to our surprise, [while] we were expecting many different kinds of microbes, it turned out that there was one kind of dominant microbe – over 90% of this culture was dominated by that one type of microbe.” At that point, Mahadevan and his team carried out genome sequencing on that dominant microbe, attempting to identify the key genes at play. They were able to identify a new strain of a microbe known as Acidithiobacillus ferridurans, which they titled Acidithiobacillus ferridurans JAGS upon their publication of its full genome in 2020. The team also started to look into ways to control the bioleaching process, engineering microbes not
$7bn
The amount that Vale agreed to pay out in compensation following the
Brumadinho disaster. BBC
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ILANA LANSKY/
Shutterstock.com
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