Researchers may be able to recycle old batteries using fungus

Scientists have found a low-cost and environment-friendly method to recycle waste rechargeable lithium-ion batteries - using fungi.

Although rechargeable batteries in smartphones, cars and tablets can be charged again and again, they do not last forever. Old batteries often wind up in landfills or incinerators, potentially harming the environment, and with valuable materials remaining locked inside.

Now, a team of researchers at the University of South Florida in the US is turning to naturally occurring fungi to drive an environmentally friendly recycling process to extract cobalt and lithium from tonnes of waste batteries. "The idea first came from a student who had experience extracting some metals from waste slag left over from smelting operations," said Jeffrey A Cunningham, the project's team leader. "We were watching the huge growth in smartphones and all the other products with rechargeable batteries, so we shifted our focus. The demand for lithium is rising rapidly, and it is not sustainable to keep mining new lithium resources."

While other methods exist to separate lithium, cobalt and other metals, they require high temperatures and harsh chemicals. Cunningham's team is developing an environmentally safe way to do this with organisms found in nature - fungi in thi3 case - and putting them in an environment where they can do their work. "Fungi are a very cheap source of labour," Cunningham said.

To drive the process, Cunningham and Valerie Harwood, both at the University of South Florida, are using three strains of fungi - Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum. "We selected these strains of fungi because they have been observed to be effective at extracting metals from other types of waste products," Cunningham said. "We reasoned that the extraction mechanisms should be similar, and, if they are, these fungi could probably work to extract lithium and cobalt from spent batteries."

The team first dismantles the batteries and pulverises the cathodes. Then, they expose the remaining pulp to the fungus. "Fungi naturally generate organic acids, and the acids work to leach out the metals," Cunningham said.
"Through the interaction of the fungus, acid and pulverised cathode, we can extract the valuable cobalt and lithium. We are aiming to recover nearly all of the original material."

Results so far show that using oxalic acid and citric acid, two of the organic acids generated by the fungi, up to 85 per cent of the lithium and up to 48 per cent of the cobalt from the cathodes of spent batteries were extracted.