Bacteria are industrious little creatures. They make cheeses, aid in the production of electrical energy, and perform important functions in the human body. Now, bacteria have another skill to add to their resume: alchemy.
It may not be alchemy in the strictest sense, but BacTech Environmental Corporation, a former mining outfit, plans to turn the toxic tailings of an abandoned Snow Lake, Man. mine into a profit using some hungry bacteria. Mixed in with the 300,000 tonne stockpile of hazardous chemical waste left over from the defunct Nor-Acme Mine is gold. An estimated $120 million worth of it, says Oscar Alvarado, Project Research Analyst at BacTech.
And it's not even a huge pile, he says, at least not when compared to some tailings piles at other abandoned mines across Canada.
Abandoned or “orphaned” mines are particularly messy problems when it comes to cleaning them up. They are closed mines whose owners are no longer around to rehabilitate them. These mines are often dormant for decades, their old tailings piles leaching harmful chemicals, like arsenic and sulfides, into the surrounding area. Sulfides, when exposed to water and air, produce acids.
So it falls to governments, and thus taxpayers, to clean them up. With an estimated 10,000 orphaned mines across Canada — over half of which are in Ontario — that can come with quite a price tag.
That is where the microscopic alchemists come in. Where once BacTech used the microbes for mining gold in Australia and China, it has now re-purposed them for mine rehabilitation. When the province of Manitoba put out a request for proposals to clean up the tailings pile that has been sitting at Snow Lake since the 1950s, BacTech submitted one.
“We were the only company to come back and say 'We'll do it for free.'”
The company says it doesn't need to charge for its services — it just keeps the gold it produces. Rather than make gold, the bacteria free it. At the plant the company is planning to build next year in Snow Lake, waste from the stockpile will be exposed to the bacteria, which will target the sulfides in the tailings. The bacteria will feed on the sulfides, releasing any other elements mixed in. In this case, it's mainly arsenic and gold.
“The reason why that pile has been there for 60 years is because it has 20 per cent arsenic and there's no real technology out there that can deal with that,” Alvarado says. “You can't roast it, you can't smelt it, you can't burn it. The arsenic content is too high. The bacteria don't really care how much arsenic is in there. They don't love it, but they're not affected by it.”
BacTech will then take the freed arsenic and bind it to iron, which is often also present in the tailings, to make ferric arsenate, a non-hazardous waste. It will then be disposed of in a clay-lined pit. With the sulfides eaten and the arsenic trapped, the company can collect the gold and a profit.
It's a long process. The Snow Lake stockpile will take seven years to remove. Then it's one down, 9,999 more to go.