Jeremy Ang, a 36-year-old engineer, holds out a cracked strip of photovoltaic cell with his fingertips: how to recycle this tangle of silicon, plastic and metals? “If no one solves this problem, the Singapore dump will overflow,” argues the young academic.
No country in the world can afford to accumulate waste, but, in the case of Singapore, the imperative is categorical. The tiny city-state is sorely lacking in space. Its scientists are therefore developing environmentally and economically viable processes to recycle the country’s waste.
Mr. Ang is part of the Scarce laboratory, the result of a Franco-Singaporean collaboration, which focuses on electronic waste. These must be disposed of with care due to their toxicity. On the other hand, they contain metals in high demand which benefit from a good resale value.
The laboratory premises, established in the Nanyang Technological University, bustle with activity. In addition to solar panels, researchers are tackling the recycling of microelectronic components, lithium ion batteries and plastics impregnated with toxic additives.
In Singapore, domestic waste is incinerated (see box). The resulting ashes are taken by barge to the island of Semakau, eight kilometers offshore, where they are piled up behind a dike. This space, created from scratch at the expense of the sea, is rapidly filling up. It will be saturated in 2035.
Rather than burning the solar panels, Ang suggests separating the layers through a combination of chemical and physical processes. He created a mechanical roller fitted with a scraper that takes off the photovoltaic sandwich. “I believe our process keeps costs and unwanted by-products to a minimum,” he explains. From there, with a bit of luck, we can scale up to industrial scale. »
Vivek Verma, another of Scarce’s researchers, is working on lithium ion batteries. He climbs a stepladder to reach the top of a crusher, where he drops a few piles. The machine transforms them into a mixture of colored, copper or blackened shavings. The objective of the following steps is to isolate nickel and lithium.
Traditionally, we tackle this task by melting the pieces, which requires a lot of energy, or by dissolving them with strong acids, an environmentally unfriendly solution. Here, the researchers use an acid extracted from the peel of oranges, explains Do Minh Phuong, an engineer of Chinese origin. “We don’t have to add any other chemicals to the solution,” she says.
Pallab Das, he attacks the plastics of electronic devices. These plastics, exposed to high heat, are often impregnated with flame retardants. Heating these chemicals generates toxic fumes. They must therefore be separated from other plastics before recycling.
The challenge is to quickly recognize toxic plastics on the conveyor belt of a recycling plant. To achieve this, the team sends a laser beam on the plastic parts. It then takes a reading of the electromagnetic spectrum of the pulverized material. “We call it quick sorting: it’s very practical in an industrial setting,” says Das. On his computer screen, we see a black spot appear: the laser has hit its target.
And the microelectronic components – resistors, inductors, capacitors – that adorn the printed circuits, how to recycle them? You have to sort them first, explains Nicolas Charpentier, another member of the lab. Whether they contain neodymium, barium or titanium, their appearance can be very similar. For now, only 1% of rare earths are recycled.
Scarce’s team has therefore created an algorithm which, from the images of optical and X-ray cameras, determines what is hidden inside the components. Mr. Charpentier starts his prototype; the treadmill activates. After passing the small parts under the cameras, jets of compressed air project them into one bin or another, depending on their composition.
“The nerve of the war in recycling is to make processes that are not expensive”, recalls Jean-Christophe Gabriel, research director at the Commissariat for Atomic Energy and Alternative Energies (CEA), in France, and co-director of Scarce, founded in 2018. People in the field are “fighting” against primary extraction of strategic metals, which costs nothing but a pittance.
Singapore is the ideal “laboratory” to meet this challenge, says Mr. Gabriel by videoconference from Europe. The simplicity of the government system — there is only one level — plays a big role. “Since there are not 10,000 layers in the mille-feuille, they go very, very quickly in their decisions. The experience is beneficial. As far as I’m concerned, I have more resources in Singapore than in France,” he says.
Should we expect that, in five years, the technologies developed by the Franco-Singaporean team will be used on an industrial scale to recycle electronic waste from the tech-savvy city-state? “I would even say the opposite: if this is not the case, we will be slapped on the knuckles,” replies Mr. Gabriel, laughing.
This report was financed thanks to the support of the Fonds de journalisme international Transat-The duty.