“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.