This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Almost all lead is recycled, among the only elements on the periodic table to earn that distinction. With good reason, mind you: the soft metal is a potent neurotoxic known to impact children's brain development, among other nasty health effects. Today, nearly all lead is used in batteries (though it was once put into gasoline, leading to widespread contamination, and, in places like Afghanistan, still is.) Most of this dangerous element is now endlessly cycled from battery to battery, thanks to stringent regulations (though enough of it ends up being improperly recycled to constitute one of the world's worst pollution problems.)
In principle, all metals are infinitely recycleable and could exist in a closed loop system, note the authors of a survey of the metals recycling field published in Science on August 10. There's a benefit too, because recycling is typically more energy-efficient than mining and refining raw ore for virgin materials. Estimates vary but mining and refining can require as much as 20 times the amount of energy as recycling a given material. Think about it: a vast amount of energy, technology, human labor and time are expended to get various elements out of the ground—and then that element is often discarded after a single use.
Lead is not alone in being recycled, of course. Aluminum, copper, nickel, steel and zinc all boast recycling rates above 50 percent (though not much above 50 percent). The same principles can be usefully applied to other materials, like plastics. After all, these ubiquitous polymers are made from another scarce resource—oil—and many are, in principle, recycleable. Yet, the overall recycling rate for plastics, grouped as a whole, is only 8 percent (as of 2010, per EPA numbers.) Take the case of polypropylene (or #5 plastic if you're checking the bottom of your food containers). The bulk of this polymer that gets recycled comes from car batteries. It is, in essence, tagging along with the lead. In other cases—water bottles, yogurt cups, you name it—it simply disappears into the nation's landfills.
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Meanwhile, the majority of elements on the periodic table—and we use almost every element on the periodic table for something or other—are also nearly completely unrecycled.
As an example, industrial ecologists Barbara Reck and T.E. Graedel of Yale University compare the fates of nickel versus neodymium. Nickel is ubiquitous, particularly as an alloy for steel. Of the 650,000 metric tons of the silvery-white metal that reached the end of its useful life in one product in 2005, roughly two-thirds were recycled. And that recycled nickel then supplied about one-third of the demand for new nickel-containing products. That means the overall efficiency of human use of nickel approaches 52 percent. Not bad, but there's room for improvement, given that almost half of all nickel is only used once before it is discarded.
Nearly 16,000 metric tons of neodymium—a so-called rare earth metal—were employed in 2007, mostly for permanent magnets in everything from hybrid cars to wind turbines. Roughly 1,000 metric tons of the element reached the end of its useful life in one product or another—and "little to none of that material is currently being recycled," the survey authors note. This despite the fact that a "rare earth crisis" stems from China's near monopoly of the neodymium trade.
Mining for neodymium is not benign (which is why the world lets China monopolize its production). And it's not just neodymium. Mining waste—or tailings, leach ponds, slurries and the like—are among the world's largest chronic waste problems. North America alone produces 10 times as much mining waste as it does the municipal solid waste (as it's known) from all the neighborhoods in the U.S. Much of that is just rock, sand and dust—the mountaintop in mountaintop removal mining. And mined products also cause waste further down the product line, such as the ash leftover after the coal is burned (the U.S.'s largest single form of waste).
This issue of profligate use gets worse: we are currently making this problem even harder to solve. How? One word: gadgets. In most gadgets you can think of, tiny amounts of rare elements are used to enhance functionality. As the industrial ecologists write in Science: "The more intricate the product and the more diverse the materials set it uses, the better it is likely to perform, but the more difficult it is to recycle so as to preserve the resources that were essential to making it work in the first place." It's as true of iPhones as it is of photovoltaic panels—and none of them have shown much success in being recycled. "End of life losses will also increase sharply soon," unless something changes, the industrial ecologists warn.
Then there are the alloys, where thermodynamics dictate that the alloying element is almost always going to be lost due to the difficulty of separation. That means the chromium used in stainless steel will usually lose its luster, for example. Worse, this form of contamination can mean that the recycled alloy can't be re-used—manganese-aluminum alloys are unsuitable once recycled for 95 percent of the uses for aluminum. As a result, "current designs are actually less recycleable than was the case a few decades ago," the authors note. Perhaps the use of such metal combinations should be minimized?
In the end, our approach to recycling is bizarre, given our resources. "Few approaches could be more unsustainable," Reck and Graedel write. In the end, we'll learn to reuse all the elements of the periodic table, or we'll lose elements to use.
Image courtesy of Barbara Reck, based on Reck et al. (2008), Env. Sci. & Tech.