Uncovering the secret stash in trash

Recycling metals from mobile phones
After their usual service life of three to four years, mobile phones can still yield significant value by recovering and recycling precious materials found inside. Image: ChameleonsEye / Shutterstock.com

Electronic products are more valuable than you think. For example, gold and silver are used in electrical contacts, solders and on printed circuit boards of smartphones. Smartphone penetration amongst Singaporeans stood at 88 per cent last year, according to a 2014 Blackbox research called “Smartphones in Singapore: a whitepaper release“. With millions of smartphones already sold in Singapore, the nation’s mobile phone users are housing hundreds of kilograms of gold and silver. However, this gold and silver are thrown out once users decide to upgrade their phones and discard their old ones.

Traditional processes of recycling are not able to pick out and recover precious materials such as gold and silver, magnets and valuable components of composite materials. As such, precious materials like carbon fibres may get damaged in the recycling process.

Challenges to recycling 

Fortunately, these precious materials may not be lost for good. Urban mining, the concept of recovering precious materials from household and industrial waste, is making this possible. After their usual service life of three to four years, mobile phones can still yield significant value. To date, according to Frost & Sullivan, worldwide recycling rates for electronics and electrical appliances are around 19 per cent. 

Recycling lowers the dependence on imports and reduces waste. However, this should not be confused with “downcycling” – a process that only produces materials of lower quality. What we should aim for is a closed-cycle waste management system where the amount of waste in the production process is minimized through the recycling of substances from waste products. There are, however, a number of obstacles to overcome before this can be achieved. 

Making sense of the mess 

A mobile handset contains less than 0.4 grams of precious metals. When the handset goes through a shredder, these materials are mixed with others, often making it difficult to separate them. 

Adding to that is the complexity of modern day electronics. Many electronic modules and lightweight products that use steel, alloys, and composite materials contain many valuable components such as gold, platinum, palladium, copper, rare earth metals, glass fibers, and plastic, but these are often tightly blended making extraction difficult.

Logical logistics

Another difficulty is the logistical effort required for recovery. For example, in Germany, 80 per cent of deregistered cars are exported, and after several more years of service they are usually scrapped without any appreciable recycling. Compared to traditional recycling, the removal of raw materials from natural deposits is much simpler in terms of logistics. 

If recycling is to become a serious source of raw materials, the processes involved need to become significantly more efficient

But demand for raw materials is increasing enormously and for some of them, such as the rare earth metals like tungsten and gallium, lack of availability may soon reach critical levels. Only small deposits of many metals have been found and most of these deposits are located in politically unstable countries. Such factors are driving the development of recycling and the expansion of closed-cycle waste management. 

Recycle smart 

Modern technology makes it possible to recover materials such as the bits of silver in RFID labels. With that in mind, Professor Stefan Gäth of the Frauenhofer Project Group for Materials Recycling and Resource Strategies in Alzenau and Hanau, Germany, advocates intelligent recycling. 

“Instead of diluting the concentration of specific materials with a shredder, we could, for example, deliberately remove the vibration alarm in order to recover the tungsten it contains,” Prof Stefan Gäth suggests. “If the composition of one cell phone is known, such processes can be automated. We are therefore creating a database with that information.” 

Efficient recycling 

In support of intelligent recycling, Dr Ulrich Bast, a materials expert at Siemens Corporate Technology (CT), suggests that easy dismantling for recycling should be a key design goal. 

If recycling is to become a serious source of raw materials, the processes involved need to become significantly more efficient. In cooperation with the Institute for Factory Automation and Production Systems at the Friedrich-Alexander-Universität in Erlangen-Nürnberg, Siemens is also investigating concepts for automating the disassembly of electric motors. 

To maximise ease of disassembling and separation of materials, a design-recycle approach is a promising option where the quick and simple disassembly of a product is planned at the design stage. For example, the aluminum frames of Siemens subway trains are held together by easily removable hexagonal bolts. The trains also contain a large amount of recycled metals, and their insulating boards are installed only between the shell and the paneling. This makes it easier to strip off when the trains are disassembled. 

Another way of efficient recycling is what Siemens healthcare has developed and calls the multi-step take-back concept. Used devices, such as X-ray machines, can be remanufactured into “refurbished systems.” Individual components will be reused or used as replacement parts, and valuable materials can be repurposed for use in new machines.

Magnetic magnificence 

Dr Jens-Oliver Müller, project leader of Project MORE (Motor Recycling) at Siemens CT, and his research team in Munich are looking for a method to recover permanent magnets, which contain many rare earth metals from compact and lightweight synchronous motors for electric cars and generators for wind power plants. 

“In MORE, we are exploring a variety of approaches to recycling. We are doing research to find out how approximately one kilogram of heavy magnets or other components of old motors from electric cars can be recovered, repaired, and reused,” said Dr Müller. 

Through the recovery of raw materials it is possible not only to produce magnets of all shapes and sizes but also to reset their magnetic properties. In addition to recycling materials, they are also looking into extending the life of products by repairing and upgrading them as well as testing to see how well a magnetic material can be reused if the presorted material are cleaned, ground, melted, made into a new magnet. 

A solvent that saves carbon fibres 

Carbon fibre is an expensive but lightweight construction material that combines the high rigidity of carbon fibres with the moldability of a plastic matrix. It is used in aircraft, spacecraft, and automobile construction. 

A Corporate Technologies expert, Dr Heinrich Zeininger is working on a way to recycle carbon fibres from fibre-reinforced composite materials. Until now, the only available recycling method was pyrolysis, which burns away the plastic and damages the fibres, causing them to become matted and tangled. At that point they can only be cut into small pieces and used to produce, for example, conducting polymers which cannot be recycled again. 

In view of this, CT scientists have now developed a “solvolytic” recycling method that uses a solvent to remove the plastic. As a result of this process, carbon fibres are left intact at their full length, woven materials keep their shape, and remain undamaged. The reuse of these fibres requires significantly less energy than would be needed to carbonize them. 

Recycling continuity 

With the demand for highly sophisticated and complex electronics on the rise, urban mining and recycling precious materials such as gold and silver is becoming a more viable option sought by many companies. With the advances and innovations made in recycling, allowing for less energy consumption, the stage is set for companies and countries to take advantage of this and indeed turn one man’s trash, into another man’s treasure.

Fenna Bleyl, a chemist and science journalist, works for Siemens’ internal communications and writes for Siemens’ media, including Innovation News or the Pictures of the Future Magazine.

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