Composting electronics: How food waste can pull rare earth materials from your discarded tech

·3 min read

In the 2017 science fiction film Attraction, an alien spaceship arrives on Earth, kicking off an unconventional love story between a human and an alien, with the fate of our planet in the balance. It hinges on the idea that we can’t control our attractions, but we might be able to bend them to our benefit.

Scientists at Pennsylvania State University are using a similar strategy in a less dramatic way, but with potentially dramatic impacts on our planet. Their new study, published in the Chemical Engineering Journal, demonstrates a novel way to recapture rare earth elements by exploiting their attractive relationship with food waste.

It’s a potential solution to a pretty serious problem. Humans create a lot of waste and we’re constantly looking for better strategies to reduce our extraction from the Earth by re-using materials we already have at hand. The EPA estimates that more than 294 million tons of solid waste were produced in the United States in 2018, and those numbers are climbing. The 2018 total was nearly a 10% increase over the previous year, and a considerable portion of that waste is comprised of electronics, otherwise known as e-waste.

Moreover, over 20% of the trash we throw into landfills is food waste. One common way people mitigate food’s contribution to our growing trash piles is through composting. Allowing food to break down in isolation from other trash, in the presence of yard clippings, microbes, and animal decomposers transforms it from putrid garbage into useful soil for gardens or farming. Unfortunately, there’s no electronic equivalent of composting. Until now.

Scientists ground up food waste from tomatoes and corn as well as wood pulp and cotton paper and soaked them in water. Chemical reactions resulted in micro and nanoparticles which have an interesting attractive relationship with metals.

In laboratory experiments, the scientists then added particles of neodymium — a material commonly used in the production of strong magnets for electronics — to a solution of water. When their food waste particles were then added to the slurry, they found that neodymium was attracted to it and captured. We’ve previously written about a similar process involving yeast to purify lead-contaminated water. The difference in charge between the organic materials and the metals causes them to bind together. There’s a similar process happening between tomato skins and neodymium.

The underlying philosophy is that electronics which have reached the end of their lifespan could be ground up or otherwise broken down and introduced to a solution of water. We could then add ground up food waste and let their natural attraction do the work of separating out rare and valuable materials for re-use. It’s a novel and useful way of re-using two of the primary contributors to landfills.

At present, the process only works on neodymium and there are certainly other electronic materials contributing to the problem of overmining and mounting trash. Scientists are aware of that, and the team is working to enhance the process in order to pull out other materials like gold and silver.

In the future, electronic devices could become increasingly sustainable owing to their strange attraction to our food scraps. That’s pretty impressive for the slop you usually sling down the garbage disposal.

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