Plastic and the circular economy. Recycling is a valuable way to recover resources, but not all recycled plastic is the same.

Plastic is often cast as the enemy to sustainability, and for many good reasons. In terms of circularity, only around 8.5% of plastics are recycled, with the highest rates in packaging (around half of all packaging bottles are recycled) and lowest in textiles. Considering metals, paper and glass are recycled at rates of 70% or more, plastic recycling rates seem very low. Why is that and how as designers can we work with it and retain a clear conscience?

Plastics are a victim of their versatility — there are so many versions and variants, it is difficult to separate and sort them. Polyethylene terephthalate (PET), polyester, is the most circular, and yet recycling rates are painfully low compared to steel, glass and paper. The problem is compounded by a process of down cycling, whereby high quality material is taken from recycled bottles into trays, textiles and films, which are recycled at much lower rates, if at all. For every 10 tons of PET bottles, 5 tons is recycled and 1.7 tons of that into new bottles. However, for every 10 tons of PET trays, such as used to package meat, <2 tons is recycled; and in the case of PET textiles, only 1 ton for every 10 tons. In the case of multi-layer films, such as used for stand-up pouches and coffee packaging, none is recycled. This is because it is impractical, if not impossible, to separate the individual materials. By contrast, for every 10 tons of steel packaging, 8.5 tons is recycled and 5.5 tons of that into new packaging; for every 10 tons of glass packaging, 8 tons is recycled and 7.2 tons of that into new packaging; and for every 10 tons of paper produced, 7 tons is recycled.

Waste plastic is generally classed as either post-consumer recycled (PCR) or post-industrial recycled (PIR). Whereas PCR material has been sold and gone through a full cycle of use, industrial scrap comes from waste generated during manufacture, such as rejects and offcuts. Both offer a valuable source of raw material for new products, but PCR tends to be more challenging to process due to the complexity of mixed waste, labels, contamination (additives etc) and plastic identification. On top of this, there are different types of PCR waste, classified by source. For example, packaging waste is reasonably abundant, has had a short life and the contamination is mainly from organic materials. This results in high quality recycled material. By contrast, waste from household appliances – Waste from Electrical and Electronic Equipment (WEEE) – is less consistent and reliable, may be contaminated with more fillers like talc and glass fibre, detergents and substances of concern (SoC), and had a much longer life. As a result, the source of recycled material will affect the visual and mechanical properties of the final compound. So whereas some parts can be designed to accommodate 100% PCR, others may be more sensitive to the visual and mechanical knock-down, unless a very ‘clean’ recycled material can be sourced. There are companies pioneering new technologies that enable the recycling of more types of plastics from complex mixed waste to produce high quality and reliable PCR plastics.

There are many different types and they are difficult to separate. Even the ones that are relatively easy to separate, like polypropylene (PP) and polyethylene (PE) because they float in water, come in many different grades. PP comes with so many modifications, such as talc and glass fibre, that only around 3% is recycled globally. The highest recycling rates are for PET, mainly due to the use of PET in clear plastic bottles. Thermosetting plastics, such as polyurethane (PUR) and epoxy, are the worst culprits, with none being commercially recycled. This is because the links formed between the polymer chains in these plastics are permanent, and cannot be undone with heat unlike the thermoplastic like PP and PE. So while they are extremely durable in application, they are also unlikely to ever be circular.

MBA Polymers based in California, pioneered methods for separating many types of plastic. Using a range of innovative processes — floatation, gravity, near infrared (NIR), electrostatic —  they take shredder residue which may be any type of plastic or composite material, and separate these by chemistry and colour. With a capacity of 150,000 tons per year, they produce a range of mechanically recycled plastic pellets that are suitable for use in new products. MGG Polymers based in Austria, which started out as a joint venture with MBA Polymers, have developed a range of techniques for separating complex post consumer mixed waste electrical and electronic equipment (WEEE). They produce a range of 100% recycled plastics suitable as drop-in replacements for virgin polymers in many cases. Polykemi in Sweden are another European supplier of 100% recycled plastics including polyamide (rPA), nylon, polypropylene (rPP), acrylonitrile butadiene styrene (rABS) and polycarbonate alloys (rPC/ABS). Campine in Austria are an important recycler of metals and chemicals, in particular batteries and lead, but also produce rPP. Ravago in Belgium produce plastic compounds with 50-75% post consumer recycled (PCR) content, including rPP, polyethylene (rPE), polystyrene (rPS) and (rABS). Morssinkhof – Rymoplast is one of Europe’s largest producers of high grade recycled raw materials, including rPP, rPE and rPET that are suitable for food contact applications. For example, their MOPET rPET comes from packaging (bottles and trays) and is turned back into food contact packaging. Nextek in UK setup the NextLoopp project to develop the systems and infrastructure needed to produce circular food-grade recycled rPP from PCR packaging. In Asia, Kingfa are one of the top providers of recycled plastics and they distribute worldwide. Their grades include recycled rPE, rPS, polyethylene terephthalate (rPET), rPP, rABS and rPA.

Samsara Eco in Australia have taken a different approach and use natural processes to help recycle plastic. They have developed a technology that uses enzymes to depolymerise plastic and revert it back to its original monomers, the chemical building blocks for new plastics. Waste material is shredded and fed to the enzymes that break the polymer chains. Additives such as pigments are removed and the monomers are reprocessed into new plastic through polymerisation. Their first product Eos Eco is a polyamide 66 (PA66), nylon 66 fibre.

The colour and graphics of recycled plastics

Recycled plastic offers significant savings in terms of CO2 emissions, anywhere between 50-90% kgCO2/kg, depending on the source and type. Even so, the global recycling averages are very low. One reason it is so low compared to other commodity materials is that mechanical recycling is only suitable for certain plastics and items that are made up of single polymers, such as PET bottles and high density polyethylene (HDPE) packaging.

While the majority goes back into products, buildings and packaging with barely a trace, some companies are taking advantage of its bright colourful properties to make bespoke new materials. In this way, materials considered as low value waste become desirable surfaces, interiors and furniture, massively extending the life of the material. Of course, there is a danger that these practices remove materials from established recycling loops, such as polyester bottles, and so cause the demand for virgin material to increase elsewhere. However, due to the deterioration of plastic with each recycling loop, as a result of the polymer chains being degraded by heating and oxidisation, these examples offer longevity to materials that may otherwise be landfill or burnt for energy recovery

Made with waste

In some cases it is possible to replace some virgin plastic with recycled waste, which may not be pure plastic. In this way, the consumption of raw materials is reduced and waste is diverted from landfill. This can be in addition to using recycled plastic. For example, UBQ recycled household waste, which is largely comprised of organic materials – everything from food residues and mixed plastics to cardboard, paper, and even dirty diapers, that would have otherwise been sent to landfill or incineration. They convert this into an additive that can be incorporated into thermoplastics such as PP and PE, creating a waste-based composite. A range of agricultural by-products and waste are converted into additives suitable for use in plastics as fillers, such as Granulous spent grain from the brewing industry, and Nature Coatings BioBlack TX black pigment from wood waste, which provides an alternative to fossil-derived carbon black. There are several other pigments derived from recycled waste suitable for fashion and textiles. Read more in the article Exploring ethical colour in fashion and textiles – promising innovations that are helping to reduce the impact of dyeing and finishing textiles.

Recovering energy from plastic waste with pyrolysis

It is estimated that around 20% of all plastic waste is burned to power generators. Plastics are made up of hydrocarbons and contain as much energy as refined fossil fuel, like diesel. It is one of the cheapest ways to get rid of complex plastic waste that is impractical or impossible to recycle, and avoids landfill. However, the fumes are toxic and simply burning the material wastes all the potential chemistry that can be recovered and reused. One step back is pyrolysis — a process of heating materials to 400-650 degC in a reduced oxygen atmosphere so that it decomposes, but doesn’t incinerate. With this technique, chemicals and compounds can be extracted from plastic waste, such as hydrogen, methane and ethylene. These can be burnt for energy, or converted into new plastics like PE. Pyrolysis can handle complex waste streams that are impractical or impossible to recycle. In this way, plastics previously destined for landfill can now provide industry with a source of energy and raw materials.