Preventing contamination in recycling

Aluminum has long been the poster child of recycling. About half of all aluminum used in the United States is now recycled, and this recycling has clear and dramatic benefits: pound for pound, it takes anywhere from nine to 18 times as much energy to produce aluminum from raw ore as from recycled material.

Because it saves so much energy - and therefore money - aluminum recycling continues to expand. But a new MIT analysis finds that this expansion could run into problems unless measures are taken to reduce impurities that can build up as aluminum is recycled over and over again: everything from paint and labels on cans to other metals that are accidentally mixed in.

Such impurities will continue to add up, the MIT researchers say, but can be managed so as to keep the accumulation to acceptable levels if extra steps are taken while the recycled goods are sorted, or during their molten processing.

MIT researchers Randolph Kirchain and Elsa Olivetti, of the Materials Systems Lab, along with Gabrielle Gaustad of the Rochester Institute of Technology, published their findings in the journal Resources, Conservation and Recycling.