What if we could get rare metals for computers and smartphones from plants? What if food and beverage waste could be used to create components for LEDs (Light Emitting Diodes)? We’re one step closer to these realities thanks to scientists from Germany’s Freiberg University of Mining and Technology and engineers from the University of Utah.
Plants absorb precious metals present in the soil into their roots, and transfer them into their shoots. Scientists from Freiberg University have developed a process called ‘phytomining’ to collect the rare earth metal germanium from energy crops such as sunflowers, corn, and reed canary grass. After the plants are harvested and fermented in biogas plants for energy, a chemical process can enable the extraction of metals. The extract is converted into organic solvents and vaporized to obtain a usable concentration.
“We’ve shown it’s efficient. And there’s been plenty of interest,” said Professor Martin Berteau, Head of Industrial Chemistry at the university. “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.”
Demand for germanium is expected to increase over the next few decades — it is used in the production of computers, smartphones and fiber optic cables, as well as infra-red light applications such as intelligent steering systems and parking sensors for vehicles. It is complicated to extract since its concentration in the earth’s crust is low. It is currently extracted as a by-product of zinc ore treatment, so obtaining it as a by-product of biogas plants would be an environmentally friendly and cost-effective way to boost supply.
Meanwhile, professors Prashant Sarswat and Michael Free and their team of engineers have created ‘quantum dots,’ components for LEDs, by treating bread, tortillas, and soda with high temperatures and pressure in specific solvents. LEDs are commonly used in appliances such as television screens and lighting for homes, city streetlights, and indoor agriculture.
“The ultimate goal is to do this on a mass scale and to use these LEDs in everyday devices,” Sarswat said. “To successfully make use of waste that already exists, that's the end goal.”
Quantum dots are crystalline structures 20 nanometers in size that have luminescent properties. They are traditionally selenium- or cadmium-based, but using food and beverage waste allows them to be carbon-based. Besides the benefits of waste reduction, this change in starting materials could result in huge cost savings given the high price point of the rare elements currently used.
“[Quantum dots] derived from food and beverage waste are not based on common toxic elements,” Free explained, “which makes their processing and disposal more environmentally friendly.”
These discoveries certainly signal a trend in environmentally preferable electronic components, particularly among university-led research. Just last month, University of Missouri researchers published achievements in creating biodegradable nanocomposites for electronic displays, a development that could help to greatly reduce electronic waste in landfills.