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 The element is a semi-conductor and was used to develop the first
transistor because it is able to transport electrical charges
extremely quickly. Nowadays, silicon-germanium alloy is
indispensable to modern life, crucial in making computers,
smartphones and fiber-optic cables.
Transparent in infra-red light, germanium is also used in
intelligent steering systems and parking sensors for vehicles.
Yet although germanium is present in soil all over the world, it is
difficult to extract, and most supplies currently come from China.
Now scientists at Freiburg University of Mining and Technology think
they have found a revolutionary way to obtain it from their own soil
- with a little help from the natural world.
Biology professor Hermann Heilmeier is one of the scientists using
common plants for this uncommon process.
 "What is being cultivated in this field are various energy crops --
for example sunflowers, corn, reed canary grass - but instead of
using them for energy purposes we want to use them for phytomining.
In German we call it 'mining with plants'. We want to bring elements
that are present in the soil into the roots and shoots of the
plants, harvest them and then extract these elements from the plants
after they have been used for energy, that is to say fermented," he
said, showing off his field of crops as he measured the moisture
levels of the soil.
The process is still in its early stages, but Heilmeier says they
have now identified the plants that could allow them to scale the
attempt up. The next stage of the process takes place in a
laboratory at the university in Freiburg, where head of industrial
chemistry Professor Martin Bertau has been overseeing the project.
He said the region is very well-suited to the extraction of
germanium due to the composition of the soil.
"There is zinc ore present here, the ground is very rich in zinc. 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. We unlock
these reserves through fermentation with the help of bacteria and
thus we are able to mobilize the germanium," Bertau explained.
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Economically, the process is efficient, because the extraction of
germanium can happen after plants are processed for use as biogas.
Thus many of the costs are already covered in existing biogas
plants. "We use the normal biogas process, collect the products of
fermentation and all there is left to do then is extract the
germanium from them. The processing costs of this downstream step
are manageable, so even with these low amounts it is still
economically viable," Bertau said.
The potential for industry could be enormous, but there is still
work to do before the benefits can be reaped. At the moment
germanium can only be harvested in extremely small quantities, just
a few milligrams per liter. Scientists need to achieve at least one
gram per liter, which at the moment is only possible through a
process of concentrating the extract.
"It is as it so often is: industry is still waiting because they
want to see a facility where everything is already working. Then
they say: 'we'll have it'. But of course we have to complete the
step in between first. Thanks to the support of the BMBF (German
ministry for education and research), we have now actually found a
solution to an intractable problem and have got to the point where
we can upscale the process. So we will be able to work with bigger
amounts, with apparatus with a capacity of 1,000 liters or 10 cubic
meters instead of 20 liters," Bertau said.
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