Materials & Applications

Urban Mining and Recycling Metals in Circular Economy

Urban Mining and Metals in Circular Economy
  1. Tokyo 2020 medal project
  2. What is urban mining?
  3. Metals that are easy to recycle
  4. Metals that are not so easy to recycle
  5. What can we do to make metals recycling easier?

Around five thousand gold, silver and bronze medals have been manufactured for the upcoming Tokyo 2020 summer Olympics and Paralympics. This sort of thing happens for every summer games, but this time an especially novel and exciting approach has been taken: all the metals in the medals have been derived from recycled computer circuit boards.

Here we explore the ins, outs and roundabouts of urban mining and circular economy.

Tokyo 2020 medal project

In April 2017, a nationwide project began in which over 90% of local authorities involved themselves. Almost 79,000 tonnes of various defunct electronics and more than six million mobile phones were collected nationwide over two years. 

Tokyo 2020 medal project
This project makes Tokyo 2020 the first in the history of the Olympic and Paralympic Games to involve citizens and to manufacture the medals using recycled metals.

These devices were then sorted, cleaned and deconstructed, with the metallic components sorted from the rest. The metallics were then chemically treated to extract the valuable gold, silver, copper and tin. Here are some numbers:

  • Collection period: from 1 April 2017 to 31 March 2019
  • Amount of devices collected: approx. 78,985 tons
  • The final amount of metals collected: 32kg of gold, 3,500kg of silver, 2,200kg of bronze
  • 100% of the metals required to manufacture the approximately 5,000 gold, silver and bronze medals have been extracted from small electronic devices that were contributed from people all over Japan.

From collection to smelting: classification, dismantling, extraction of gold, refining operation and obtaining pure gold:

What is urban mining?

This is a great demonstration of the incredible potential that circular economies can have. Dubbed the “urban mine”, from both economic and ecological perspectives, the gains are incredible. The choice of circular recycling over purchasing gold alone saved $1.8 million and kept over 450 tonnes of CO2 out of the atmosphere. 

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Urban mining is the process of extracting of raw materials such as metals or precious metals from waste and metal scrap. Precious metals such as gold, silver, platinum or palladium can be extracted from old mobile phones and computers. Urban mine is a stockpile of rare metals in the discarded electronic equipment.

The numbers are astounding; 50 million tonnes of e-waste are produced each year, and left unchecked this could more than double to 120 million tonnes by 2050.

Metal economies are especially profitable when circularised, aided by the fact that the metals are often 100% recyclable. As opposed to other materials, such as thermosetting plastics or paper, re-melting is often all that needs to be done to rework metallic items into raw materials. 

However, while many of the more common metals are recycled in this way, others are not. The increasingly in-demand lithium, for example, experiences recycling rates of less than one per cent. 

Metals that are easy to recycle

Electronic waste
EPA report revealed that by recycling 1 million cell phones, we can recover more than 20,000 pounds of copper, 20 pounds of palladium, 550 pounds of silver, and 50 pounds of gold.

Manufacturers involved with steel, copper and aluminium know this phenomenon well and have been recycling material from the beginning. For years, items ranging from automobiles and electrical wiring to aluminium cans have been collected, cleaned, melted and refined back into fresh new metals, ready to be made into new objects. 

Metal scrap
Iron and steel are the world's most recycled materials, and among the easiest materials to reprocess, as they can be separated magnetically from the waste stream.

This ease of recycling reflects the morphological simplicity of these metallic objects. The metals are relatively pure in all three cases, excluding minor contaminants that are burned off during smelting, such as paint. 

Metals that are not so easy to recycle

In comparison, materials that are tightly intermingled can be incredibly difficult to recycle — for example, those found in lithium-ion batteries, aluminium-thermoplastic composites, and even simple plastic-laminated disposable coffee cups

Processes used to recycle these materials are often wasteful and require more time, reagents, power and supervision. Fundamentally, it’s a question of economic viability. 

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What can we do to make metals recycling easier?

This is where design engineers can lend a hand by cleverly designing their products to make recycling as simple as possible. This can be achieved in several ways. For example:

  • using plastic snaps or ultrasonic welding that hold devices together instead of screws
  • removable plastic inserts for sandwich cartons and coffee cups; or by ensuring that devices are simple to disassemble into their constituent parts.  

Lead-acid car batteries are a standout example of this potential. Mature recycling schemes have found they have a recovery rate of more 99% cent in some cases, partly due to their clever and modular design.   

Lead-acid batteries are highly recyclable, with many countries achieving recycling rates of more than 90 per cent. However, that doesn't mean they can go into the waste bin at home. Toxic substances like lead can leak into the environment when car batteries and other lead-acid batteries end up in landfill.

Whereas circular economies are well-established for some metals, they still have some way to go for others. Metals like steel, lead, copper and aluminium are leading the field, but there is plenty more that manufacturers, consumers and recyclers can do to improve upon existing, wasteful linear models. 

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