About half of all the aluminum used in the United States is being recycled these days, which is great news – but there’s a catch. Although a lot of energy is saved in the recycling process — since it avoids the need to make new aluminum from raw ore — it turns out that the recycling process, when repeated, creates serious impurities in the end product. Researchers at MIT found that unless specific processes are introduced into the aluminum recycling market now, those impurities will continue to add up, resulting in a glut of impure recycled aluminum which has extremely limited uses.

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When aluminum — or another material — is recycled, impurities result – sometimes from the degrading of the material itself but often from other outside factors like paint on the outside of cans and other metals that get accidentally mixed in. Those impurities can build up over time and the resulting recycled aluminum will get relegated to uses where that impurity can be tolerated. MIT researchers found that there are technologies available today that can reduce the resulting impurities during the recycling process. Right now, the degradation of aluminum isn’t a huge problem but as it goes through more recycling cycles, impurities will grow and these technologies will become more and more necessary to continue the recycling loop.

“We’re continuing to collect more and more scrap,” MIT researcher Randolph Kirchain said. He notes that, “we’re likely to have more and more problems” as aluminum is sent through more recycling cycles. As of now, the variation in quality has not been a problem as impure aluminum is sent to uses where it’s ok for it to be slightly contaminated, however as that aluminum comes back through the cycle it could become unusable. “If material comes in that’s more contaminated, they’ll divert that toward more forgiving applications,” Kirchain explained. “There is a huge range of impurity tolerance,” said Elsa Olivetti, of the Materials Systems Lab. “The question is, how will the balance of such markets over time compare with the kinds of materials coming through the recycling stream?”

The researchers recommended that as new aluminum factories are erected these available technologies should be built right into them, even if they aren’t needed now. The team warns they will be needed in the future and for the long-term viability of the business the technologies will become imperative. The team explained that specialized uses like electronic circuits and aerospace materials require pure aluminum while engine blocks can tolerate impurities. As these things are recycled, however, the amount of aluminum available for engine blocks will become overwhelming while the more specialized aluminum will decrease in availability. The technologies they’ve gathered and outlined in a paper in the journal Resources, Conservation and Recycling could reinvigorate the aluminum industry down the line and increase the availability of pure, recycled raw materials.


Photos by Ecov Ottos and ElizaIO on Flickr