Scientists from the Freiberg University of Mining and Technology in Germany have developed a method called 'phytomining' to harvest the rare earth metal germanium - used in computers and smartphones - from energy crops such as sunflowers, corn and reed canary grass. In brief, plants harvest precious metals which are present in the soil, and these transfer (along with essential nutrients) into the roots and eventually the shoot of the plant. Harvested plants are first fermented in biogas plants for energy. The scientists then extract the precious metals through a chemical process: as only diminutive quantities of Germanium can be produced using this approach, the extract is converted into organic solvents, and these are then vaporised to obtain the desired concentration.
According to Professor Martin Berteau, Head of Industrial Chemistry at the University, the area of Freiburg is ideal for these experiments as the ground is rich in zinc, from which germanium is primarily mined: “We have the remains of waste rock piles from mining, which germanium-rich water can drain better through. And when you cultivate plants here and give them that water, they can build up germanium reserves through normal physiological processes”.
Germanium is used in the production of computers, smartphones and fibre optic cables, as well as infra-red light applications such as intelligent steering systems and parking sensors for vehicles. The precious metal exists widespread around the globe but is complicated to extract. Currently, most of the supplies are provided by China.
Demand for germanium is likely to escalate within the next decades with the growth of smart devices. As yet, commercial production is not feasible as the concentration of the metal in the earth crust is low. In the US, Russia and China, germanium is extracted as a by-product of zinc ore treatment. From an economic perspective, phytomining offers a promising alternative.
According to the researchers, the method has the potential to transform commercial mining of precious metals, as it is environmentally friendly and cost-effective, as a by-product of biogas plants. Berteau says: “We’ve shown it’s efficient. And there’s been plenty of interest. But industry is still taking a wait-and-see approach. They’d like a fully operational facility and then they’ll go for it. But we still have to get to that point.”
However, the production of biogas from crops needs to be balanced against food production, with fierce competition for land, water and soil nutrients. Add to this the interests of a huge and rapidly growing technology industry, and there could be worrying implications for claims on available land. What mechanisms are needed to safeguard the availability of land to meet pressing global challenges, such as access to nutrition?
Image Credit: derson2011101 / flickr
Reuters (2015, September 7) Smart phone ingredient found in plant extracts
Deutsche Wellle (2015, September 13) Phytomining - raw materials from plants
TU Bergakademie Freiberg (n.d.) PhytoGerm
TU Bergakademie Freiberg (2012, Juli 18) Startschuss für das r³-Projekt PhytoGerm zur Erforschung von Germanium in Biomasse
Djoko Noumodje Patrice (n.d.) World Food Security: Challenges and Opportunities of Biogas Production in the European Union