Thanks to mobile phones, computers, and other electronic waste, there’s so much gold in the average urban landfill that sometimes dumps can be up to 50 times richer than an actual gold mine. Most of the wealth that goes into making electronics–around $21 billion in gold and silver alone, each year–ends up being lost, in part because some electronics don’t get recycled, and in part because current recycling methods are messy and inefficient. One unlikely solution: Using natural fungi to recover precious metals from the trash.
Mycelium, the root-like part of a mushroom that can be seen growing under logs in the woods, can be crushed into a fine powder and treated to help filter gold out of phones and other electronics. Researchers at the VTT Technical Research Centre in Finland recently pioneered the new process.
Typical electronics recycling is already big business; one recycling plant in Guiyou, China, processes 1.5 million tons of e-waste every year, bringing in $75 million. But the whole process just doesn’t work particularly well. A standard extraction procedure uses toxic chemicals like cyanide and a lot of energy, but only recovers about 20% of the gold from electronics. With a fungus filter, though, a recycler could get as much as 80% of the gold back.
The fungus method might also save some money. “The filter itself is quite inexpensive–it’s a fungi that anybody can grow,” says Olli Salmi, one of the researchers who led the study. “We haven’t scaled it up yet, so we have no experience of how it could work on an industrial scale. But in decentralized locations, on a small scale, we’ve seen that it works quite well.”
It doesn’t entirely eliminate the use of chemicals–the fungus itself is chemically treated to help attract the gold, and the electronics are also bathed in a solution first. But the researchers are experimenting with less harmful alternatives. “In the same project, we looked at a non-cyanide extraction of gold,” Salmi says. “So you’d escape the dangerous cyanide processing and replace it with a more sustainable process.”
Eventually, the process could potentially be used both in industrial facilities and in outdoor dumps in places like Ghana, which imports hundreds of thousands of tons of e-waste each year. Right now, electronics there are burned in a crude process that releases plumes of toxic smoke, and treated with chemicals that leach into water supplies–all to obtain only a tiny fraction of the valuable metals inside.
So far, the researchers have only tested the process with gold, but they plan to soon try it with copper and several other rare metals that are commonly found in electronics.
While the researchers will continue to work on improving their new mushroom-fueled process, they say that better product design can also help make recycling easier. “Design for disassembly would help the problem, of course,” Salmi says. “You can design components so you can take them apart easier.”
It’s also possible that someday gadgets will rely less on rare materials like gold, so we won’t have to keep throwing so many of those materials away. “There’s the substitution question–how could we substitute something less scarce or expensive for the materials we currently use?” Salmi asks. “Carbon nanotubes are already known technology for replacing some of the rare earth metals, so it makes discarding less troublesome.”
For now, there’s ample opportunity to use the Finnish researchers’ method. By 2017, we’ll likely be throwing out 30% more e-waste than we already are, or about 72 million tons a year–approximately the weight of 200 Empire State Buildings. That’s a lot of gold.