Micro-Mining: Bioleaching Extracts Metals

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Green, Non-ferrous Metals

Mineral-hungry bacteria can turn their favorite treats into valuable metals, leached from low-grade ores.

These bacteria, using minerals as their main energy source, “squeeze out” metal ores and concentrates while metabolizing mineral snacks. Known as bioleaching, this process has already made waves in the metals industry; in fact, 20 percent of mined copper comes from the process. Facing high demands from the electronics industry, the copper industry expects to see even more bioleaching business. “The method is emerging as an increasingly important way to extract valuable minerals when conventional methods such as smelting can’t do the job cheaply enough,” National Geographic says.

 
Photo: Bioleaching tanks.
Credit: BioMinE Consortium.

More eco-friendly than smelting, bioleaching uses less energy than smelters and doesn’t cause the toxic output that smelting creates. In addition, companies can use the process for smaller ores, those without enough copper for the usual refining procedures.

In an insightful article on the topic, National Geographic notes that another process, heap bioleaching, relies on the same bacteria. During heap bioleaching, “copper sulfide ore is crushed and put on an impermeable pad,” the magazine explains. “An acidic solution containing bacteria is applied and allowed to percolate through the heap, draining into a collecting pool. In a few months, the bioleaching is complete, with 80 to 90 percent of copper extracted from the ore.”

Codelco, the world’s largest copper producer, recently helped create Chilean venture firm BioSigma to better understand these microorganisms and improve the bioleaching process. Codelco expects to create a full industrial plant to properly utilize the bacteria next year. Over the next ten years, Codelco plans to produce 10,000 tons of copper annually through bioleaching.

“We are now able to know what microorganisms are present in a sample and how many of them are alive and doing their job,” Ricardo Badilla, general manager of BioSigma, told National Geographic. “These tools enable us to control and modify a bioleaching operation at the industrial level.”

Although Chilean state copper company Codelco has a two-third stake in Biosigma, Japan’s Nippon Mining & Metals Co. owns the remaining one-third, and both companies play a leading role in this promising research. In May, Codelco produced its first copper cathode from bioleaching. Just last month, the company approved a $17 million capital increase for the venture, which means bioleaching is here to stay.

–Amy Edwards

Comment (1)

  1. very nice
    do you know some plant working with copper concentrate bio leaching to produce copper.
    we are involving in one with 50000 t/y copper production.

    regard
    mehrdad zamani

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