A presentation to the American Chemical Society’s fall meeting has revealed how fungi can extract valuable materials from batteries that would otherwise go to waste.
The batteries in smartphones and laptops, particularly the cathodes, contain a lot of lithium and cobalt. Methods exist to recycle these elements, but they are currently more expensive than mining new material. Consequently, a lot of old phones end up in landfill, while Earth's reserves are depleted. Without recycling, cobalt shortages, in particular, could represent a limitation on battery production and the shift to clean energy.
Professor Jeffrey Cunningham and Professor Valerie Harwood, both of the University of South Florida, have put three species of fungi to work, drawing on the chemicals they release to extract metals at an affordable price.
Aspergillus niger is normally seen as an enemy to humanity, causing black mold on fruits. Penicillium simplicissimum has already been put to use leaching zinc from metal oxides and even breaking down polyethylene. Penicillium chrysogenum is possibly humanity's best fungal friend, as the first source of penicillin rich enough for mass production.
"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 in a statement. "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."
Batteries are too solid for the fungi to get at them without assistance, so the team dismantled the battery and pulverized the cathodes. This is a cheap process compared to the high-temperature activity currently required. Then the fungis' organic acids go to work. "Through the interaction of the fungus, acid, and pulverized cathode, we can extract the valuable cobalt and lithium. We are aiming to recover nearly all of the original material," Cunningham said.
Unfortunately, this is not the end of the process. "We have ideas about how to remove cobalt and lithium from the acid, but at this point, they remain ideas," Cunningham said. "However, figuring out the initial extraction with fungi was a big step forward."
Although lithium-ion batteries are currently mostly used in consumer electronics, demand is expected to rise rapidly as production of electric cars soars. Even among the competing technologies to store stationary energy from intermittent sources such as solar cells or wind turbines, lithium-ion batteries are a leading contender.
With the Tesla Gigafactory soon to produce lithium batteries on an unprecedented scale, the challenge of recycling components is likely to become urgent a few years later as products wear out. Combined with the possibility of making battery anodes out of mushrooms, the future could be fungi-powered.