Sustainable materials in consumer electrical and electronic products – how to design for recycled and recycling to extend the life of materials.

The amount of waste electrical and electronic equipment (WEEE) produced each year is around 50 million tonnes (2020) and growing rapidly around the world. The design and manufacture of things like mobile phones, televisions, kitchen equipment, toys and computers — intended to make them as desirable and affordable as possible — means they tend to be very difficult to recycle end of life. But the end of a product’s life should not be the end for the materials; instead it is the start of a new chapter.

Electrical and electronic products are made up of a complex mix of plastics, elastomers and metals, electronics, batteries and screens; all of which contain valuable resources that can be recycled and reused if the constituent parts can be separated and identified. Today, the main economic driver for WEEE recycling is based on recovering precious metals such as gold, silver, palladium and copper. By designing products from recycled material, and designing them for recycling end of life, increases the likelihood of circularity.

Product categories for recycling

The effectiveness of design for recycling depends on context and how products are sorted and processed end of life. While in packaging these divisions are well-defined and understandable for everyone — plastic bottles, card boxes, tin cans and so on — consumer electronics can be more difficult. The categories include temperature exchange equipment (cookers, fridges etc), screens, large equipment (white goods for example), lamps, small equipment, and small IT equipment. Each of these is treated differently in recycling centres, because the material make up varies. For example, a fridge contains liquids and insulation, whereas small equipment is mostly metal components and electronics; and whereas a cooker might be 90% metal, a TV may contain 50% glass and only 5% metal.

As a result, large items are often disassembled, and this helps to separate the individual materials. By contrast, small items are simply shredded to extract the valuable metals. There are several companies making recycled material from white goods, such a high impact polystyrene (HIPS) fridge liners. Smile Plastics in the UK produce a range of recycled sheet materials suitable for furniture, retail and interior projects. Likewise, Plasticiet in the Netherlands produce bright and colourful sheets from post consumer recycled fridge liners and industrial waste. The Good Plastic Company, also in the Netherlands, produce a recycled polystyrene (rPS) sheet called Polygood. The produce a range of bright and speckled colours, including bespoke blends to suit different projects.

Small equipment may be crushed to allow for pre-sorting by hand, such as removing batteries and valuable items like PCBs and electric motors. As a result, the housing is often shredded and mixed with other waste and residue, from which it can be difficult to separate. While ferrous (like steel) and non-ferrous metals (like aluminium and copper) are relatively straightforward to extract from mixed waste, plastics can be much more challenging due to the huge range of types and additives in use. Another important consideration is how different materials are joined. For example, if plastic is permanently joined to metal, then it is likely to be ‘sacrificed’ (burnt off) during the process of recycling the metal. Dissimilar metals can be more problematic, because one may contaminate the other during processing. For example, mixing cast and wrought aluminium, whose chemistry is optimised to suit the very different types of forming process, can lead to down-cycling of the recycled material. Dissimilar plastics permanently joined together—by welding, stacking or adhesive bonding—cannot be recycled. Instead, they will be incinerated for energy recovery or landfilled.

Therefore, design for recycling as a process can follow two routes. Either the individual materials are put together in such a way that they are straightforward to separate (such as with screws or snap fits), or the materials are assembled in such a way that they do not require disassembly prior to recycling. The latter route requires a deeper understanding of the recycling processes and may only be feasible in a closed loop system. To give an example from the packaging industry, milk cartons in the UK which are blow moulded polyethylene (PE), have coloured lids to identify the fat content: full, semi or skimmed. The amount of pigment used in the lid has been set low enough that when recycled together with the plastic bottles, it becomes so diluted that it does not visibly affect the colour.

Steel

Worldwide around 1.85 bn tonnes of steel is produced annually, with around 35% of raw materials coming from recycled scrap. In theory, all new steel could be made from scrap, but there is not enough and the longevity of products made from steel means material going into products today may not be recycled for years or even decades. The majority of iron ore, the raw material for steel production, comes from Australia, Brazil, China, India and Russia. In blast furnace basic oxygen steelmaking (BOF) process up to around 30% scrap steel is added as a cooling agent, absorbing excess heat from the exothermic decarbonisation process and thus helping to reduce the overall carbon footprint. In electric arc furnace (EAF) steelmaking, up to 100% scrap is used to make new steel products.

End of life steel recycling rates are around 85%. It is relatively economic and straightforward to separate from mixed waste because it is magnetic. During the steelmaking process most impurities present in scrap can be removed (burnt off). However there are some elements, like copper, which degrade the quality of steel and so are removed where possible during sorting. During the design process it is possible to specify a high proportion of recycled steel, because the properties are like new and highly predictable. Components should make the most of steel’s relatively high strength and stiffness. Automotive and construction are two industries that have learnt to make the most of novel high strength steels to reduce weight, and thus minimise the consumption of resources.

Aluminium

Annual production is in the region of 56 million tonnes, 18 of which comes from recycled scrap (32%). It is widely cited that recycled aluminium uses as little as 5% of the energy and emits only 5% of the greenhouse gas as virgin. This over-simplification smooths over the fact that virgin aluminium is incredibly energy intensive to produce. As an example, more than 10 times the energy is required to produce 1 kg aluminium versus 1 kg carbon steel. At 1.1 giga-tonnes CO2 emissions, the aluminium industry is responsible for around 1% of total manmade greenhouse gas emissions. Considering around 40% of the impact of aluminium is from the production process, but 60% from electricity power generation, the source of energy can be more important, in terms of carbon footprint (greenhouse gas emissions), than the raw materials and proportion of recycled content.

Aluminium recycling efficiency is around 75% worldwide, boosted by the very high rate of aluminium can recycling – within around 60 days, an aluminium drinks can goes through a full cycle of production, use and recycling, ready to be consumed allover again. Aluminium is extracted from mixed waste using an eddy current separator. Once the ferrous metals have been extracted using magnets, repelling forces are created by permanent rare earth magnets. Eddy currents are introduced into non-ferrous metallic particles, and the alternating magnetic fields help to separate them from non-metallics like plastic and glass fragments.

Plastic

According to Plastics Europe (A circular Economy for Plastics, 2022), the total amount of recycled plastic used in new products averages 8.5%, with electrical and electronic products using 2.9% on average. It is significantly less than the amount of metal being recycled. This is a direct result of how the plastics industry has evolved and the way these materials behave in recycling and disposal. Additionally, there are concerns about the safety of some plastic recycling. Mechanically grinding plastic into small pieces suitable for separation and recycling generates large quantities of microplastics, which often end up contaminating wastewater. There is also a risk that plastics contain substances of concern (SoC), as well as substances of very high concern (SoVHC). For example, polytetrafluoroethylene (PTFE) is used as an anti-dripping agent in plastic used in electronics such as headphones, earbuds and speakers. It helps to achieve the required level of flame retardancy. PTFE uses polyfluoroalkyl substances (PFAS) in its production. These hazardous ingredients do not degrade or break down, known as ‘forever chemicals’, they are shown to be extremely persistent in both the environment and in the human body. They are toxic and known to be carcinogenic.

Unlike steel and aluminium, the plastics used in consumer products tend to be very difficult to recycle into material of the same value, because they comprise a complex mix of technical engineering polymers and additives. The chemistry is optimised to provide very specific visual and mechanical properties like colour and transparency, toughness and impact strength, sealing, tactility and strength-to-weight. It is impossible to separate the thousands of different grades and mixes in use, and so recycled material will be a blend including various additives, pigments and enhancers. In addition to this, plastics tend to oxidise at high temperature (such as when melting and moulding). Additives are incorporated into the material to reduce the negative impacts, but they are consumed by the process. This means that with each heating cycle, the quality of the material is degraded. This is very different from metal, which can be melted and reformed many times without any loss of mechanical properties.