How food waste can extract rare earths from your discarded technology

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

Pennsylvania State University scientists 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 journaldemonstrates a new way to recover rare earth elements by harnessing their attractive relationship to food waste.

This is a potential solution to a fairly serious problem. Humans create a lot of waste and we are constantly looking for better strategies to reduce our extraction from the Earth by reusing the materials we already have on 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 growing. The 2018 total represented an increase of almost 10% over the previous year, and a considerable portion of this waste consists of electronic devices, also known as electronic waste.

In addition, more than 20% of the waste we throw in landfills is food waste. Composting is a common way for people to lessen food’s contribution to our growing waste piles. Allow food to decompose in isolation from other waste, in the presence of garden clippings, microbes and animal decomposers transforms it from putrid garbage into useful soil for gardens or agriculture. Unfortunately, there is no electronic equivalent of composting. So far.

The scientists ground up tomato and corn food scraps as well as wood pulp and cotton paper and soaked them in water. Chemical reactions have resulted in micro and nanoparticles that have an interesting attractive relationship with metals.

In lab experiments, the scientists then added neodymium particles – 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 suspension, they discovered that the neodymium was attracted to it and captured. We have previously written about a similar process involving yeast to purify lead contaminated water. The difference in charge between organic materials and metals causes them to bond. A similar process occurs between tomato skins and neodymium.

The underlying philosophy is that electronics that have reached the end of their lifespan could be crushed or otherwise broken down and introduced into a water solution. We could then add the shredded food waste and let its natural attraction do the work of separating rare and valuable materials for reuse. It’s a new and useful way to reuse two of the main contributors to landfills.

Currently, the process only works with neodymium, and there are certainly other electronic materials that contribute to the problem of overuse and waste buildup. Scientists are aware of this and the team is working to improve the process to extract other materials like gold and silver.

In the future, electronic devices may become more and more durable due to their uncanny attraction to our food scraps. That’s pretty impressive for the mud you usually throw in the garbage disposal.

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