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Education & research

BHMZ Freiberg

Ore Mountains

The discovery of rich silver deposits some 850 years ago turned Freiberg into a mining town and made the margraves of Meissen rich. Although the silver reserves in the Erzgebirge mountains were exhausted long ago, mining still plays an important role in the town – not least because a team at TU Bergakademie is successfully conducting research into new techniques for extracting raw materials. Scientists are now focusing their attention on strategic elements such as germanium and indium, both of which are much scarcer and more sought after than silver. But in future there will be no need for miners with hammer drills to extract these precious metals – bacteria will do all the work.

Biochemistry instead of heavy equipment

“Our research project has very little to do with the traditional methods of extracting raw materials used in mining,” says Helmut Mischo. As Chair for Underground Mining Methods at TU Bergakademie, he heads the research into the extraction of indium using microbial leaching. In this process, rock containing ore is flushed with a bacterial solution. The bacteria leach the precious ore from the rock, and it is then recovered from the solution in the next stage of the process. The advantages of this technique are obvious: there is no need to move the rock or bring it up to the surface of the Earth, and waste rock is no longer piled up in huge spoilheaps outside the mine like it used to be. Mischo points out that this allows huge energy savings. What’s more, this technology is also a “purely biological process, as these bacteria occur naturally underground,” explains PhD student Ralf Schlüter. He and his colleagues identify and multiply the most efficient strains of bacteria and develop technologies to harvest the ore. “Technical and logistical issues need to be solved, and biochemical processes are also required to separate the ore from the bacteria,” says Professor Mischo.

These new processes are particularly useful for recovering rare elements such as germanium or indium. Both elements were originally discovered in Freiberg, and indium is one of the rarest metals on Earth. It has a number of uses, including as a transparent conductor in flat display screens and touch screens, and demand for it is increasing around the world.

Prof. Dr.-Ing. Helmut Mischo
Prof. Dr. Klaus-Dieter Barbknecht and Dr. Erika Krüger

Public research, private funding

Professor Mischo’s project in the research mine at TU Bergakademie Freiberg is one of 13 sub-projects being undertaken at the Biohydrometallurgical Center for Strategic Elements (BHMZ). All of the sub-projects revolve around processes that extract metals in a modern, efficient and environmentally friendly way. If the research activities in Freiberg prove successful, it could be possible to recover rare metals without any hard physical work or environmental damage in the not too distant future.

Ensuring the new techniques can also be used commercially is always a priority for the researchers in Freiberg. That was the aspiration of Dr Erich Krüger, whose foundation has been funding the first five years of the Krüger Research School at the BHMZ since 2013. Helmut Mischo is confident that the findings from the first funding period will be sufficient to secure further financial support from 2018 onwards. “The next step will involve converting our technology into an application suitable for industrial use,” he says.

Visit the website of the BHMZ here.

All photos by Detlev Müller.