Microorganisms to extract raw materials from e-waste

Millions of tons of e-waste are generated every year: smartphones, computers, radios. They contain important raw materials such as copper, gold, or rare earth metals. It is often not worthwhile to recover them, and the e-waste is incinerated. The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB has developed a bio-based process to recycle valuable raw materials.

Recovery of metals using biomining, or RüBioM for short, is the name of the project at the Stuttgart-based Fraunhofer Institute. Microorganisms are used to extract the metals from the e-waste.

First, the e-waste is shredded. The scrap particles are then placed in a bioreactor together with microorganisms such as Pseudomonas aeruginosa. This is a notorious rod-shaped bacterium that can cause infections and is classified by the World Health Organization as an antibiotic-resistant hospital germ.

Microorganisms produce acid

However, for the Fraunhofer project, the microorganism has a useful property: it produces acids and other compounds that dissolve the metals contained in the e-waste. This process is called bioleaching.

At the end of bioleaching, a metal-containing solution remains. In a second step, this is processed using microalgae: they absorb the metals, which can then be recovered.

According to Fraunhofer IGB, the biological process makes it possible to selectively recycle specific metals. The team initially focused on palladium, an element from the platinum group metals. Tests were also conducted with neodymium, a rare earth metal used, for example, in strong permanent magnets. An advantage of the biological process is that it works without toxic chemicals and at low temperatures.

“The results of the feasibility study are encouraging,” summarizes project leader Lukas Kriem. With palladium, bioleaching released more than 13 percent more metal than a chemical process. Using biosorption, more than 30 percent of the palladium could subsequently be extracted from the solution.

With neodymium, there are “positive initial approaches,” said Kriem. However, the results currently “cannot compete with chemical processes” - not yet, the researcher emphasizes.

Mining with plants and viruses

Bioleaching and biosorption are not the only biological processes for recovering raw materials. So-called phytomining uses plants to absorb metal ions from the soil through their roots. The process was originally used to clean up contaminated soils. For about 30 years, researchers have also been testing metal extraction in this way. Viruses are also used for mining.

The process developed by Fraunhofer IGB is intended to contribute to a circular economy and reduce Europe's dependence on raw material imports. “Sometimes the treasure is not deep underground, but right in our drawer,” says Kriem.

However, the work is basic research. According to the researchers, there is still a lot to do before bioleaching and biosorption are ready for industrial use. The Fraunhofer team will present its work at IFAT, the leading trade fair for environmental technologies in Munich, next week and is searching for partners from the waste management and industrial sectors for follow-up projects.

(wpl)