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Published on September 30th, 2015 | By: April Gocha, PhD

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Green mining technique uses photosynthesis to extract semiconductor germanium from soil

Published on September 30th, 2015 | By: April Gocha, PhD

[Image above] Credit: Mark, Vicki, Ellaura and Mason; Flickr CC BY 2.0

 

 

The new green mining technique for germanium is, quite literally, green.

 

The technique, called phytomining, uses plants to extract difficult-to-mine semiconductor germanium from the ground.

 

Germanium is used in most gadgets and devices that make our current world current—including computers, smartphones, sensors, and fiber optics.

 

But germanium is difficult to extract from the earth, even though it’s abundant in soils worldwide. Most of the current supply of germanium, like many rare earth elements, comes from China.

 

Scientists at Germany’s Freiberg University of Mining and Technology, however, have figured out that they don’t have to dig up the earth to extract the element—they can make plants do the work for them.

 

Phytomining is nothing new, but using it for germanium extraction is. Previous efforts have focused on mining other elements, such as gold or copper.

 

“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,” says biology professor Hermann Heilmeier in a Reuters news article. “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.”

 

In addition to making the mining easier, the process is doubly green in that the plants can first be used to for biogas production. That means the process would make use of a waste product, ensuring that the biomass is utilized for several usable end products.

 

“And when you cultivate plants here and give them 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,” Freiberg professor and head of industrial chemistry Martin Bertau explains in the article.

 

The scientists aren’t yet ready for industrial scale-up, but the initial stages of the project indicate it may be feasible. Hear more in the video below.

 

Credit: UKRAINE TODAY; YouTube

 

Currently, the technology is limited to small quantities of extracted germanium—milligrams per liter, the article says. For the technique to be industrially feasible, the scientists need to boost its efficiency considerably, up to at least one gram per liter.

 

But even though the scientists have considerable work to do, they’re still optimistic about the process.

 

“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 says in the article.


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