Fungi have an interesting property: Many species are surprisingly good at dealing with exposure to heavy metals. This has been observed for some time, and it’s one of the main reasons that fungi are used all over society to extract metals from things like industrial fly ash, or runoff from processing plants. If you pick your species right, fungi can be abundant and quick to replicate, cheap to buy and keep alive, and best of all they tend to be rugged, and so don’t require much in the way of care.

Now, logically enough, this approach is coming to battery recycling. The difference between this and historical efforts is that most industrial processes produce a lot of metal in relatively few individual places — big spigots of metal-laced water, decommissioned large pieces of machinery, or enormous piles of industrial waste. With lithium ion batteries, the bounty is split between hundreds of millions of devices that need to be collected and processed. But with lithium, cobalt, and other expensive battery materials needed in such large quantities, it will increasingly make sense to look for companies to look at old batteries to replenish their stocks.

The technique requires that the batteries be opened up and the cathodes (made of lithium and cobalt in the form of LiCoO2) be pulverized before exposure to the fungi, a cocktail of Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum, which have been used to extract metals in other contexts for some time. They produce organic acids including oxalic acid and citric acid, and these acids can extract up to 85 percent of the lithium and up to 48 percent of the cobalt from the cathodes of spent batteries. Other of the fungal products, however, like gluconic acid, were ineffective.

The “extraction” refers to leaching the metals into the acidic slurry created by the fungi; from there, the metals still need to be reacted extracted for later use — but precipitating free metal ions out of water is one thing industry has gotten very good at over the years.

The fungal approach is also under consideration for recycling of the precious metals in more general electronics scrap material, though it faces similar challenges to do with centralizing and preprocessing the scrap before metals can be extracted. In that case, it’s not the bulk silicon that presents a cost barrier, but the much more exotic rare earth metals that can often be extracted from so-called “e-waste” and put to use once more — easing not only the expense, but also the human cost of extracting these natural resources.