The lithium inside your smartphone battery probably came from a huge brine pool in South America or a mine in Australia. But as demand surges—Tesla's new Gigafactory, alone, plans to use essentially the entire current world supply of lithium for electric car batteries—researchers are trying to figure out better ways to recycle the material instead.

One solution might come from fungus, which can naturally eat up old batteries and spit out lithium, along with cobalt, another valuable material.

Unlike existing methods of recycling rechargeable batteries, a fungi recycling plant could potentially be both cost-effective and safer for the environment. "The existing methods tend to use harsh environmental conditions, strong acids that are not necessarily great for the environment or for health if there's a human exposure to them," says Jeff Cunningham, an environmental engineering professor at the University of South Florida. "There can be toxic emissions from the current processes."