Topic

PCB recycling issues

End-of-life board recycling

We have discovered that the CRT recycling problem runs into hundreds of millions of units. The question now arises as to what one can do with the associated printed circuit boards.

Activity

What is the scale of the problem as regards boards as distinct from final electronic products? What is in or on a board that would make it worth processing? And what can you turn a PCB into?

After exercising your imagination on the last two of these questions, try a web search using the terms recycling +"printed circuit boards".

Review your answer as you read further.

Whilst data on the total amount of electronic scrap produced is available, for example from Industry Council for Electronic Equipment Recycling (ICER) http://www.icer.org.uk/, data for scrap boards is less readily available. However, an interesting ‘scoping study’ on what one can do with scrap boards may be found at this web site.

Quote

“50,000 tonnes of PCB scrap is produced each year in the UK and of this only around 15% is currently subjected to any form of recycling. The remaining 85% is consigned to landfill. Currently, the only board waste being recycled is the proportion having an inherent value because of its precious metal content and this is limited to recovery of the metal content via smelting.”


Goosey and Kellner, August 2002

 

 

We can recover all the metallic elements on a printed circuit board such as the copper (and any nickel) and the tin and lead from the solder. There may also be smaller quantities of precious metals, such as gold, palladium and silver. Flame retardants can also be recovered. However, there may be hazards associated with certain types of components, containing mercury or beryllia.

But what is worth recovering? Certainly gold, palladium, silver and copper can earn revenue, but the other metals recovered are hardly in worthwhile quantities. However, whilst most populated boards and bare boards with a precious metal content have a value that exceeds the cost of processing, in other cases the costs of refining may exceed the intrinsic value of the metal.

The normal process for recycling a board starts with disassembly and component recycling where possible. Certainly any hazardous components need to be removed before the board is shredded and granulated by machine, separating metals from the plastic and fibres that constitute the majority of the board. Metals can then be recovered by a variety of separation processes and passed to refiners, and the plastic and fibre residue either incinerated or sent to landfill. The current way in which this is organised is indicated schematically in Figure 1.

Figure 1: Flow chart for recycling an electronics assembly, Goosey and Kellner

Flow chart for recycling an electronics assembly, Goosey and Kellner

Unfortunately, economic forces mean that much of this work is currently exported to countries such as China, where labour costs are lower and health and safety restrictions less onerous. More sophisticated approaches, specifically looking at hydrometallurgical treatments, are being investigated by Imperial College and at Cambridge, with the aim of providing a solution before 2006.

Of course with printed circuit boards there are one or two alternatives. For example, you can turn your spare boards into coasters or even into a golf club (http://www.circuit-pro.com/), although one wonders how much new resin is used and solid waste produced during the fabrication process for the latter. There is also a limit to the number of coasters and golf clubs that could realistically be produced!

In the US, the non-metals portion of circuit boards is currently being used in several industries to enhance products. In plastic lumber, it gives strength to the “wood”; in concrete, it adds strength, making the concrete lighter, and providing an insulation value ten times that of standard concrete. It is also being used in the composite industry as filler in resins to make everything from furniture to awards plaques – “This unique product gives the appearance of marble and granite”.

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Plastic drum recycling

Somewhat more immediately successful than the initiatives for PCB recycling is the plastic drum recycling project, which is trying to reduce the environmental impact of the 12M new 25 litre drums consumed in the UK each year, each containing 1–2 kg of plastic. The project has both to research the way these drums are distributed throughout the UK, from the point of view of collecting and recycling the materials, put together appropriate recycling schemes, and then propose how this can be done, given that there may well be toxic residues in the drums.

Probably the most difficult aspect is creating new products for the recycled material. A number of products have been identified that can be made from 100% recycled material, plus some colorant. By compacting drums, so that 72 drums can be crammed onto a single pallet, it has been possible to cut transport costs, and there is a commercial market for the material – £100/tonne is paid for granulated material designated for use in subsoil drainage.

A final comment

Reviewing a number of these recycling projects, it is clear that their success or otherwise depends critically on economic factors, and that these may change according to the marketplace. Such changes have been behind the demise in recent years of initiatives to collect waste paper, where an oversupply led to collapse in the market price, making separate collection appear uneconomic.

But does this equation fully take into account the environmental cost?.

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