Has recycling failed as a solution to the plastic pollution crisis?

For many years, criticisms of plastic recycling – as a concept and as a solution to our plastic pollution crisis – have been offered. With the possibility of a global plastics treaty arriving by the end of this year, these arguments warrant consideration, especially with Greenpeace among their proponents. For its critics, plastic recycling remains, despite decades of effort, an unproven intervention because the toxicity and variety of contemporary plastics makes them inherently unsuitable for recycling. In this year’s Big Plastic Count, Greenpeace claim that of the 1.7bn plastics binned each week (90bn annually), 58% was incinerated, 11% landfilled, 14% exported and just 17% recycled. So, will plastic recycling always be a dead-end – or does it have some part to play in a circular future? 

Recycling plastics preserves, creates and releases toxins 

Funded by the Norwegian Research Council and run by a group of Norwegian and Swiss research organisations, the PlastChem project created a database of over 16,000 chemicals and polymers used in the production of plastics around the world, concluding that more than 4,200 were 'of concern because they are persistent, bioaccumulative, mobile and/or toxic.’¹ Crucial to the functioning of the materials, some of these hazardous chemicals will be preserved when plastics are recycled. A paper published in the Journal of Hazardous Chemicals gives examples of potentially toxic substances from various plastic products that are capable of being released: phthalates, brominated flame retardants (BFRs), bisphenol-A (BPA), bisphenol-A dimethacrylate, lead, tin and cadmium, formaldehyde and acetaldehyde, 4-nonylphenol, MTBE (methyl tert-butyl ether), benzene and various volatile organic compounds.² Typically, the concentrations released are typically below regulated levels - but sometimes they are considerably higher and the authors suggest that guidelines tend not to consider the low levels at which endocrine disruption occurs nor the particular toxicity of mixtures. But plenty of these substances remain in recycled plastics, claims another study which calls them ‘legacy substances’, finding BFRs, phthalates, PTE (a form of PFAS) and VOCs.³

Worse, however, is that recycling (specifically, pyrolytic recycling) can add new toxins to plastics. In Greenpeace’s report Forever Toxic: The Science on Health Threats from Plastic Recycling, the authors cite research that when plastics are heated during pyrolysis recycling processes, BFRs become brominated dioxins and common stabilisers are oxidised.⁴ But mechanical recycling can be no less problematic, as certain research has shown that recycling the most widely recycled plastic PET#1 which has been collected with other waste can, in certain cases, produce plastics with concentrations of acetaldehyde that make it unsuitable for food-contact applications – as in, when “recycled”, PET#1 can become too toxic for its original use!⁵ 

Even worse, plastics recycling actually releases toxins directly into the environment. During thermal degradation, nitrogen-containing plastics (e.g. nylons, polyacrylonitrile, and polyurethanes) release highly toxic hydrogen cyanide; chlorine-containing materials (e.g. PVC) release hydrogen chloride and dioxins; and fluorine-containing polymers (e.g. polytetrafluoroethylene (PTFE) and polyvinylidene fluoride) release poisonous hydrogen fluoride and perfluoroisobutene, one of the most toxic simple alkenes.² A 2013 study discussed in Greenpeace’s report found elevated levels of air pollutants in and around plastic recycling facilities in China, which may have a variety of impacts on workers and locals.⁶ Another study from China found increased concentrations of flame retardants in soils around plastic recyclers.⁷ In 2021, the International Pollutants Elimination Network (IPEN) and Arnika found that chicken eggs produced around e-waste and plastic waste recycling yards were among the most contaminated with POPs (persistent organic pollutants) of the sample, taken from 25 different global locations.⁸

Contemporary plastics are too various to sort 

When it comes to recycling, plastics have to be thought of in entirely different terms to materials like glass, stone or metal. Most plastics are absorbent but when it comes to pretty much every other property, each of the thousands of plastics is thoroughly different – and their absorbency only exacerbates this variety, allowing all of the different plastics to blend together when co-collected to create new categories that need separating. (Not to mention, contamination by the rest of the waste with which plastics are collected!) So, plastics are a waste management worker’s worst nightmare, requiring endless vigilance and a sprawling range of different sorting bins.  

In their article Plastic Recycling Doesn’t Work and Will Never Work, former EPA administrator Judith Enck and founder of the Last Beach Cleanup Jan Dell use the example of typical fast-food packaging to illustrate this sorting nightmare – but let’s take the most generous possible angle. Let’s say there’s three of you and you get some drinks, one hot, one cold and one bottled. Your bottle will be polyethylene terephthalate (PET#1) but let’s be generous and say that the other two come in paper cups. What about the lids, though? Well, for the hot drink, it’ll probably be polystyrene (PS#6) and for the cold drink, polypropylene (PP#5). Immediately, each of these plastics must remain separate from each other in the recycling process. But let’s say that on your way home, you nip into a supermarket and grab a box of brownies in a clear clamshell container. Despite being made of the exact same PET#1 resin used in your friend’s bottle of water, the way that it’s made, through thermoforming rather than blow-molding, has changed its properties to such an extent that it can no longer be recycled with bottles of the same material. Keep adding all of the dimensions of colour, mixture, additives, etc., that you’ll find in a typical collection of household plastic waste and you’ll begin to see just how difficult it is to even sort plastic waste into the different batches that can be recycled together.  

‘Advanced’ plastic recycling is mostly just incineration 

Like mechanical recycling at its best, chemical recycling (sometimes called ‘advanced' plastic recycling) offers the potential of full circularity, allowing plastics to be de-polymerised into new feedstocks. So far, in actuality, the dominant method of chemical recycling is pyrolysis, which is a fancy name for decomposition by fire.  

In 2022’s Circular Claims Fall Flat Again, Greenpeace discusses a document filed with the EPA regarding a pyrolytic recycling plant in Ashley, Indiana with which the local government was working to conduct plastic recycling. Figures on this document state that about 70% of the feedstock (plastic waste) is effectively incinerated, with the remaining 30% splitting into waste char (10%) and pyrolysis oil (20%), which will later be combusted, too. Other similar cases are cited in Greenpeace’s report. In one of the studies cited early, the authors report that in Europe, more plastics waste is destined for this form of fuel-creating pyrolysis recycling (39.5%) than for actual recycling (29.7%).² So, currently, pyrolytic recycling and its product, pyrolysis oil amount to a slower paced form of incineration. 

Whilst many new players in the sector suggest that there is a concerted effort to redirect energies towards the creation of new plastic feedstocks through pyrolysis and other solvolysis methods (as a recent report in Nature details), Greenpeace believe that despite decades of effort, these methods remain unproven at any real scale. In the absence of such technologies, then, it seems foolish to gamble on their future development by continuing to produce vast quantities of unrecyclable plastics – indeed, this appears to be Greenpeace’s position. The most important first step to solving the plastic pollution crisis, they say, is a drastic reduction in the volumes of new plastic being produced through bans on all single-use and (what they regard as) unnecessary plastics.  

¹ State of the Science on Plastic Chemicals: Identifying and addressing chemicals and polymers of concern. Wagner et al. The PlastChem Project. 2024. 

² An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling. Hahladakis et al. Journal of Hazardous Materials. 2018.

³ Plastic waste reprocessing for circular economy: A systematic scoping review of risks to occupational and public health from legacy substances and extrusion. Cook et al. Science of the Total Environment. 2023.

⁴ Identification and Evaluation of (Non-)Intentionally Added Substances in Post-Consumer Recyclates and Their Toxicological Classification. Rung et al. Recycling. 2023.

⁵ Effect of recycled content and rPET quality on the properties of PET bottles, part I: Optical and mechanical properties. Brouwer et al. Packaging Technology and Science. 2020.

⁶ Pollution characteristics and health risk assessment of volatile organic compounds emitted from different plastic solid waste recycling workshops. Huang et al. Environmental International. 2015.

⁷ Environmental pollution of polybrominated diphenyl ethers from industrial plants in China: a preliminary investigation. Deng et al. Environmental Science and Pollution Research. 2016.

⁸ Plastic Waste Poisoning Food and Threatening Communities in Africa, Asia, Central & Eastern Europe and Latin America. Petrlik et al. IPEN. 2021.