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You may not be particularly familiar with terms such as germanium, cobalt or rare earths, but you probably encounter them more than you realise in your daily life. This is because these are the raw materials used to manufacture the components and devices we need in today’s era of digitisation and renewable energies: fibre optic cables, mobile phones and flat-screen televisions, photovoltaic cells and batteries for electric cars. In other words, most of us come into contact with raw materials such as these in our everyday lives. Consequently, they are in considerable demand in the high-tech industry. But what should be done when such "strategically important" raw materials are no longer available in sufficient quantities or are only available at exorbitant import prices?
Plants as a source of minerals
One possible alternative is to use plants. Rather than digging deep into the earth, advantage could be taken of the fact that plants draw minerals from the ground through their roots. Botany professor Hermann Heilmeier and his colleagues at TU Bergakademie Freiberg have discovered that barley and wild grasses enrich particularly large amounts of germanium. They have even developed a method of extracting the minerals: after harvesting, the plants are fermented and then burnt. The metalloid is extracted from the ash – as yet the yield is small, at 100 grams of germanium per ton. "A lot of fine-tuning is still needed to make the technique more cost-effective", explains Heilmeier, adding that the extraction process needs to be improved and higher-yield plants found. At present the Freiberg researchers are experimenting with reed canary grass, a promising variety that is grown as an energy crop in Scandinavia.
Raw materials from the oceans
Another place where valuable raw materials can be found is at the bottom of the sea. The "Blue Mining" consortium, funded since 2014 by the European Commission, has its sights set on deposits in the deep sea. Polymetallic nodules, for instance. These potato-sized rocks cover the deep-sea abyssal plains of the Pacific and Indian Oceans. In future, it may prove possible to extract not only manganese from them, but also nickel, copper, cobalt and rare earths.
How can these mineral resources be exploited?
The 19 companies and research institutions in the consortium, which include the technical universities in Aachen and Freiberg, the Helmholtz Centre for Ocean Research (Geomar) in Kiel and the Federal Institute for Geosciences and Natural Resources (BGR) in Hanover, have set themselves quite a task. Although scientists in the 1970s already explored whether and how the sea floor might be "harvested", the technology needed to do so has yet to be developed. "Marine floor mining could function in much the same way as potato harvesting in agriculture", says Sebastian E. Volkmann, a mineral resources engineer at RWTH Aachen University’s Institute of Mineral Resources Engineering. The idea is to pick up the polymetallic nodules using a self-driving track-driven "collector", pump them up onto a ship using a vertical transport system and then process them on board. Individual components of this technical concept are currently being developed and tested in small-scale trials.
Whether it is a question of harvesting the deep seas or tapping into the wealth of resources in plants, it would appear that we have not yet exploited all the potential ways of obtaining raw materials. Which is good news, as this not only gives rise to exciting research projects, but also makes our planet ready to face future challenges.
Blue Mining is a research project funded by the European Union. It is exploring the technical processes and strategies that would be suitable for mining marine resources. An international consortium made up of a total of 19 companies and research institutions active in different fields is jointly researching sustainable mining concepts.www.bluemining.eu