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• The world has been shifting away from wasteful incandescent and harmful fluorescent lights and increasingly adopting light-emitting diode (LED) technology, which promises to reduce carbon emissions.

• Yet despite widespread adoption of the technology, virtually no LEDs are currently recycled or reused for their parts.

• To counter this problem, researchers are exploring ways in which LEDs can be designed for reuse and repair, as well as improving the efficiency of recycling.

 

The past decade has seen a paradigm shift in the way the world looks at lighting. Homes, offices and streets have turned off wasteful incandescent lights and fluorescent ones that exposed users and the environment to toxic contamination. 

In their place, climate scientists and governments have promoted light-emitting diode (LED) bulbs to tackle ballooning electricity consumption, of which about 20% is from lighting, making up 6% of global carbon emissions. Without the adoption of LEDs, global energy consumption for lighting could swell 60%  by 2030.

Thanks to the use of the material gallium nitride, which produces blue light and won its inventors the Nobel Prize in Physics, LEDs use roughly 75% less electricity and last 25 times longer than previous forms of lighting.

“Blue LEDs are fantastically efficient,” says Rachel Oliver, a professor of materials science at the University of Cambridge. In 2017, analysts at IHS Markit, a climate information service, said the switch to LEDs was responsible for a reduction in emissions of half a billion tons of CO2 that year — equivalent to shutting down 162 coal-fired power plants.

LEDs constitute over half of light sales around the world, according to the International Energy Agency, which puts lighting on track for hitting its net-zero scenarios by 2030. That also leaves a lot of room for growth. On top of that, people and businesses are using more lighting than ever before, so the technology chosen to illuminate society will likely need to be rolled out in much greater numbers than what currently exists. Speed is also important, as the IEA estimates that a net-zero scenario depends on LEDs accounting for all lighting sales by 2025.

Despite widespread adoption of the technology, around the world, virtually no LEDs are recycled or reused for their parts. Most of the development of LED lights takes place behind closed doors and researchers have been surprised to discover which materials end up in the lights they buy.

The road ahead for the LEDs will be shaped by the ability to engineer lights that are suitable for recycling, to make them last as long as possible and to reduce the harmful effects that light pollution has on human health and ecosystems. Finding the materials necessary to produce them could make companies rethink both mine waste and post-consumer waste.

“Gallium nitride is a very good material for making very efficient lights, and we want very efficient lights because that is a good way of reducing carbon costs,” says Oliver, who also directs the Cambridge Centre for Gallium Nitride. “So how do we make them live longer so we don’t have to use as many? And how do we make them so that they are designed for recyclability from the start?”

Precious materials
The success of LEDs hinges on more than just gallium and nitrogen, which exist as just flecks in LED lights. Bulbs, tubes and strip lights that use LEDs bring together a dozen metals sourced and shipped from around the world, typically to countries in Asia for manufacturing. Many of these materials are produced in tiny quantities as byproducts from mining. All told, LED lights that fit in the palm of your hand are delicate creations of more than a dozen elements.

Electricity enters an LED bulb through copper wires, reaching one side of the diode and attracting the other side to share electrons. The combination of the two materials produces light, and with additional indium and aluminum, the diodes are more likely to combine and produce brighter light. Soldered onto a printed circuit board with gold, cobalt, antimony, magnesium, arsenic and cadmium and yet more gallium.

The diode itself only produces blue light, but yellow and orange hues are often more preferable indoors. An additional phosphor, or transparent layer containing yttrium, aluminum, garnet and some cerium filters out blue light, leaving colors closer to white. Combinations of barium, strontium, cadmium and europium can produce red colors, and cerium and lutetium can produce more yellow-green shades.

Scientists are focusing efforts on researching phosphors that could produce healthy forms of light. Too much blue light can decrease the production of melatonin and disrupt human sleep cycles. Blue light also penetrates water deeper than other wavelengths of light, which has been found to prevent reproduction on coral reefs and distort biological clocks.

The materials are then encased in a carcass of plastic, aluminum and glass, which make up the majority of material by weight. When an engineering team in Brazil deconstructed LED bulbs to estimate their value to recyclers, they were surprised to find high concentrations of precious and critical metals. The concentration of gold per ton of bulbs was 16 times higher than in typical natural ores. This year, researchers in India estimated that one ton of just the diodes contains materials equivalent to 7.8 tons of gallium ore, 3.2 tons of indium ore and 42 tons of gold ore.

The heavy burden that LEDs place on mining arises because many of the elements in LEDs are extracted as byproducts from ore that contains very small concentrations of each element. Until recently, there has been little understanding about where some of the most important components of these lights come from. Plentiful resources are out there, experts say, and it’s just a matter of finding them.

Gallium mainly comes from bauxite ore, which is used to produce aluminum. After bauxite is smelted to produce alumina, a company can choose to take an extra step to extract its gallium components before they are lost to waste when it is refined into aluminum. Even so, just 10% of the gallium in ore can be recovered.

Gallium is also used in the printed circuit boards in LEDs and many other electronics. As the smartphone market becomes saturated, however, the LED share of the market is likely to show the biggest growth, says Brian Jaskula, a specialist in gallium at the U.S. Geological Survey.

Like gallium, indium production doesn’t top 1,000 tons in a year. If a refinery doesn’t extract it from zinc ore, it ends up as waste, typically dumped in a waste or tailings pile. Often it is so invisible in ore that companies ignore it. Both gallium and indium are on the lists of critical materials in the US, Canada, Australia and the EU.

“If we’re moving it and mining it already, then surely from a sustainability viewpoint it’s better to extract it than just dump it in a waste pile and have to revisit it later,” says Simon Jowitt, a geologist at the University of Nevada Las Vegas. Jowitt has worked to develop methods to identify places in the world where such “byproduct metals” could be extracted from waste or from currently operating mines.

Byproduct materials are difficult to trace before they are fully extracted as a marketable product. China dominates the production of indium and gallium, because of its strong aluminum and zinc industry, but it imports the elements in concentrates sourced from around the world. Its bauxite comes mainly from Guinea, Australia and Indonesia, a supply chain built up after domestic environmental regulations made mining bauxite too costly. In China’s largest supplier of bauxite, Guinea, companies displaced locals to build mines, and after a military takeover the government pressured China to pay higher royalties for its mining.

Indium supply is murkier, and experts are left to infer the source of indium from the sources of zinc and the producers of indium, which are mainly China and South Korea.

Sustainability potential
With the ubiquitous rollout of LED lights, there is a great potential for efficient recycling and recovery of materials. Extending the life of the materials in an LED can also extend the benefits from environmental and social costs embedded in the LED. While LEDs’ unseating of incandescent and fluorescent bulbs has also largely removed toxic metals like lead and mercury from homes, many still rely on arsenic and cadmium, and some still use lead. When LED lights are sent to landfills, these metals can find their way into waterways or harm wildlife.

The most valuable piece of an LED bulb is the gold circuitry, but extracting it is expensive compared with the cost of mining. While the other materials have monetary value, it doesn’t compete with the market prices for freshly mined materials. Gallium, for example, has long been cheap, as China’s booming aluminum industry has enabled an oversupply of gallium, says Jaskula.

“The gallium nitride chip can be recycled, but once that chip is put into an LED and the LED goes to the consumer, that gallium is never recycled,” says Jaskula of the USGS. “If people think they can make a profit recycling, they will find a way. If money can be made, that’s what gets things done.”

Oliver of the University of Cambridge investigated the causes of LED bulb failure, and in almost all cases, the diode was not the issue. “Basically we found that the LEDs still worked perfectly, but things that surrounded them, like the wires that attached them to the outside world, had come off,” she says. LEDs that are tossed out may still have a functional diode that could be reused. Extending the life of an LED depends on the mechanics of the plastic and aluminum framing, but the IEA notes that it could also gut companies’ business models to continually sell lights.

In India, one of the largest markets for LED lighting, citizens adopted the technology at a rate that surprised even the most hopeful proponents. However, most LED lights came from China, where the pressure to reduce costs also led to a reduction in quality. Lifetimes for bulbs shrunk from 8 years to 3 years at the same time that LEDs spread around the country.

Due to the design of LEDs with minuscule components, current recycling processes are unable to convert them into reusable materials at a level acceptable to business. A simulation of material recovery using available technologies in 2020 found that it was only economically viable to recover 55% of the materials. Methods are improving, and researchers note that public awareness about deconstruction and recycling systems can ameliorate problems.

However, recycling should be the last resort of all circular economy techniques, according to a review of LED designs and recycling technologies. Companies, consumers and governments may focus on repairing and reusing the materials in their current form, considering the diodes can last a few decades and the frames degrade more quickly. For example, researchers have proposed that users could trade in frames and save their diodes to last several times longer. Circuit boards that unclip easily or diodes that can be electrochemically separated are other potential design options to make bulbs more easily recyclable.

“I am glad to say that all the research in this area makes it very clear that the dramatic energy improvements of LEDs far outweigh environmental concerns, and I encourage people to upgrade to LEDs, even if they are not yet perfectly recyclable,” says Heather Dillon, a mechanical engineering professor at the University of Washington Tacoma, who has studied the performance of lighting products.

 

Article Source: news.mongabay.com