Recycling in the STEM Classroom

girl recycling and text saying "Science and the STEM Classroom looks at the STEM lessons to be found in recycling."

Our oldest son will be a senior in high school next year. (Deep breath.) All Delaware public high school students must perform 60 hours of documented volunteer work for a non-profit group as a requirement for graduation. With a little nudging from me, our son chose Habitat for Humanity. New Castle County’s Habitat chapter runs a ReStore, where homeowners and contractors donate new or gently used home parts, like windows, flooring, sinks, tile, and furniture. The donated items are sold at very reasonable prices to other members of the community for use in their homes. The boy has found his niche, and wants to keep volunteering there as long as he can. They’re happy to have him, since he’s built like a lumberjack and can carry like one too. Having a way to keep cabinets, doors, and windows out of landfills is a great help to the environment and got me thinking about the many STEM elements in recycling programs of all kinds. This month we’ll take a tour around the world, and dip into geology, hydrology, technology, environmental science, chemistry, economics, global politics, and ethics.

Bottled water

Yes, bottled water has borne the brunt of criticism from environmentalists for years. If you don’t have a refillable aluminum, glass, or plastic jug on your desk by now, you’re doing it wrong. We all know how much energy it takes to make those ubiquitous thin plastic, half-liter bottles. (Approximately 3 to 5 million joules each, to be specific.) Beyond the cost of plastic production are the added factors of transportation, distribution and refrigeration at the point of sale. Bottled spring water comes from sources all over the world, including Fiji and the Alps. Getting that water to your refrigerator adds significantly to its costs.

In addition to the environmental impact of bottled water consumption, another issue is economic. Did you know that almost 55% of bottled water is glorified tap water, not spring water? It’s almost the same thing you can get from your own faucet at any time. What’s worse, is that a number of large bottled water companies are located in California, which is experiencing record drought conditions. Water privatization is an issue that should concern everyone. Approximately 10% of the world’s water is currently under private control and this percentage is expected to grow as municipalities look for ways to reduce the cost of maintaining aging infrastructure. Privatization removes this cost from the government’s balance sheet, but puts the water supply under the control of a corporation, which has the sole aim of making money for its shareholders. When more than 1 billion people in the world lack access to safe drinking water, this seems short sighted at best.

Tap water in the United States has an average cost of US$2 per 1000 gallons. When you consider that the average wholesale cost of bottled water in the United States is US$1.21 per gallon, you can see that choosing a bottle over a glass in your own kitchen makes very little sense. If the taste of your home’s water bothers you, consider buying a filter for the tap or a pitcher with a built-in filter. You’ll come out ahead on cost, and the environment will benefit too. The current recycling rate for water bottles is about 39%. The rest of the bottles end up in landfills or as trash in the environment. The water bottle industry has worked to reduce the amount of plastic in its bottles as a nod to environmental responsibility, but these measures have also reduced their costs.

Rare earth elements

A number of modern technologies depend on the 17 rare earth elements. The vast majority of rare earth element production is currently in China. China possesses approximately 50% of global rare earth element reserves. Because China has relatively large quantities of these elements while also having the advantages of lax environmental controls and cheap labor, it dominates the market. Rare earth elements became an issue of national security in 2010 when China allegedly placed an embargo on exports of these materials to Japan in response to an offshore border dispute. Japan is the largest market for rare earth elements, as much of the consumer products that use them are made there.

Many of the products that depend on rare earth elements are recent inventions. Some of the most well-known products are cell phones, solar cells, electric cars, and wind turbines. Rare earth elements became necessary in the mid-1960s when color televisions needed brighter red pixels. A particular valency state of europium produces red light by phosphorescence. This also makes europium useful in compact fluorescent light bulbs.

Perhaps the most important use of rare earth elements is in permanent magnets. Permanent magnets do not become nonmagnetic once the magnetic field is removed. These permanent rare earth magnets are very powerful and some can retain their magnetic properties at high temperatures, making them invaluable to industries like aerospace and defense, health care, clean energy and electronics. If you’ve ever undergone magnetic resonance imaging (MRI), you’ve had the warning about wearing clothes without metal fasteners. The magnets are so powerful that they can pull on any iron-containing object in the body. On occasion, this attraction can cause the iron-oxide pigment in tattoos to heat up and cause first-degree burns. (To be honest, I thought this was a myth and I’m quite surprised. The things you learn!) Please note that this effect is rare and no good reason to skip an MRI.

One of the biggest problems with rare earth element mining and refining is the waste products. A principal byproduct of rare earth element production is radioactive thorium. A number of the other waste products from rare earth mining are similarly toxic. Baotou, in Inner Mongolia, China, is widely contaminated with these toxic waste products. Two-thirds of the 97% of rare earth elements that come out of China are produced in Baotou. China’s market dominance allows the government of China to dictate the price of rare earth materials, but this economic power has come at a price. The ground in Baotou is saturated with toxic waste, and a huge tailings pond dominates the landscape. The farmers have moved away. The factory workers that remain experience various health issues.

These environmental concerns and supply issues have led to important research on rare earth element recycling. Current recycling methods are expensive and have their own undesirable byproducts. But innovative research in Japan uses salmon sperm to recover rare earth elements in an aqueous process that is more environmentally friendly. Because of the particular market constraints on these vital elements, it’s important to develop a viable recycling method.

Recycling in the future

The United States has made significant improvements in recycling rates in the last 20 years. But the overall recycling rate in the United States is still less than 40%. There is no federal recycling legislation in the United States, but 47 of the 50 states have disposal bans to keep at least some items out of landfills. Recycling has also increased in importance globally. It may surprise you to know that about 70% of the world’s electronics wastes are exported to China. Recycled materials supply 40% of the world’s raw material needs, but the energy and CO2 savings vary by material. Austria has the best overall recycling rate, recovering 60% of total recyclable materials. Brazil has the next best rate, at 50% of all waste. Greece has the lowest overall recycling rate, at 10%.

Aluminum (or aluminium, depending on where you learned to spell) is one of the most common recycled materials. More than a third of global aluminum production today comes from recycled materials. This is important because recycled aluminum uses as little as 5% of the energy and emits only 5% of the greenhouse gases of primary aluminum production.

Glass is another common recycling target. Glass can be recycled forever. Recycling a glass jar saves energy because recycled glass melts at a lower temperature than the original components. Switzerland recycles 91% of all manufactured glass. This is currently the best recycling rate for a single commodity.

Recycling is becoming a high-tech industry. RFID tags on household recycling bins and the collection trucks can provide information about neighborhood participation rates, allowing cities to tailor incentive programs to low participation areas. RFID tags on the regular waste bins paired with scales on the collection trucks would also let municipalities accurately charge households for the cost of waste disposal. Most bottled water is consumed on the go, so strategic placement of recycling bins in dense urban areas could increase participation rates. Another area of technology with important future implications is solid waste gasification for energy recovery. Currently only 2% of the energy in solid waste is recovered.

Produced by the National Science Teachers Association (NSTA), science writer Becky Stewart contributes monthly to the Science and STEM Classroom e-newsletter, a forum for ideas and resources that middle and high school teachers need to support science, technology, engineering, and math curricula. If you enjoy these blog posts, follow Becky Stewart on Twitter (@ramenbecky). Fans of the old version of The STEM Classroom e-newsletter can find the archives here.

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