Upcycling and downcycling: what is a label worth without measurement?

The terms upcycling and downcycling now appear at every level of the plastics industry, from laboratory papers to product labels. In a wide-ranging perspective article, three researchers from the University of Manchester ask what “up” and “down” actually mean when a plastic gets a new life. Their answer is uncomfortable. Assigning a direction is usually a value judgement rather than a measured result, and that can hold back circularity or even enable greenwashing.

In short: Upcycling and downcycling labels are, in most cases, based on value judgements rather than measurement. A perspective published in Cambridge Prisms: Plastics uses three case studies to show that the same process can be read as upgrading or downgrading, depending on the point of view. The authors therefore argue that life cycle assessment and techno-economic analysis should come before any direction is assigned.

Who wrote the study, and why revisit it now?

Up, down and back again: Value judgements in polymer recycling is authored by Claire L. Seitzinger, Ciaran W. Lahive and Michael P. Shaver, all of the University of Manchester. It was published on 6 February 2026 in Cambridge Prisms: Plastics, a journal of Cambridge University Press, as an open-access article under a CC BY 4.0 licence. It is often described as a “Cambridge study”, but Cambridge is the publisher; the research was done in Manchester. Funders include the Royal Academy of Engineering, the BBSRC and EPSRC research councils, and the European Regional Development Fund. The authors declare no competing interests.

We covered the paper’s headline message when it came out, in our piece on the linguistic trap in waste management. This time we go deeper: through the case studies and methodological proposals, and into what they mean for waste management practice in Hungary.

Two Earths, two kinds of circularity

The authors open with a thought experiment. On Earth A, every object becomes itself again: a bottle becomes a bottle, a T-shirt a T-shirt, an office chair an office chair. Earth B runs a spiral system. A bottle becomes a take-away container, then a T-shirt, then an office chair. Finally the material is chemically broken down to monomers and made into a bottle again. On both Earths, sorting is perfect and waste management is fully optimised.

The question is simple; the answer is not: which Earth stays habitable for longer? The paper’s “spiral economy” figure illustrates Earth B with concrete lifetimes. A yoghurt pot is in use for weeks, a car part for around 12 years and a park bench for about 25 years. Then comes pyrolysis, whose hydrocarbon output can return to packaging production or move on to paints and fuels.

Mechanical and chemical routes: where does “up” begin?

The study builds on the R-framework described by Reike and colleagues. A plastic counts as end-of-life once it reaches R7 (recycle) or higher, meaning that reduction, repair or remanufacture are no longer possible. At that point, landfill and incineration are terminal from a material perspective. The authors therefore focus only on mechanical and chemical recycling.

Mechanical recycling does not intentionally change the polymer’s chemical structure. It is the backbone of today’s systems: collection, sorting, washing, shredding, extrusion and pelletising. Chemical recycling has two main branches. Non-selective routes (pyrolysis, gasification) yield broad mixtures of molecules that can feed conventional crackers. Selective routes (chemocatalytic or enzymatic depolymerisation) break specific bonds.

The authors note that upcycling and downcycling labels get attached to any of these routes, regardless of technology. Their starting point is the 2022 definition by Helbig and colleagues: downcycling is the quality reduction occurring during or because of recycling, expressed in a thermodynamic, functional or economic way. The Manchester team would add an environmental dimension as a requirement.

Upcycling would then be the mirror image, a quality increase along the same lines. In practice, though, the word can mean creative reuse, turning waste into anything of “higher value”, or, in industry, specific chemical transformations. The study observes that hardly any original research paper calls its own process downcycling. That label tends to be handed out by review articles, for routes such as textiles to rags or plastics to park benches.

The yoghurt pot: recycling, upgrading or downgrading?

The first case study is the polypropylene (PP) yoghurt pot. We did not buy the pot, we bought its contents, so once it is empty its perceived value collapses. As food-grade PP it has a defined composition, and mechanical recycling preserves much of its original quality. With perfect sorting, cleaning and reprocessing it could become a pot again. That would be the pure “re” category.

But a pot’s life is short. The same polymer chains soon enter another processing loop and suffer thermo-mechanical and thermo-oxidative damage each time. If pots cannot be collected and cleaned separately, keeping food-contact accreditation becomes nearly impossible, and polymeric contaminants accelerate polyolefin degradation. The paper cites three industrial efforts to solve this:

• CleanStream: formerly Berry Global, now Amcor; a sorting process with a UK plant.
• PureCycle: solvent-based purification that dissolves and filters out contaminants.
• NextLooPP: fluorescent tags on labels for more precise sorting.

These can restore food-grade quality, but at extra economic and environmental cost.

The alternative is to turn the pot into a car part, which stretches its useful life from weeks to around 12 years. Automotive-grade PP has different specifications, however, so this transition needs development work. From a polymer-chain perspective, the authors argue, both routes, pot-to-pot and pot-to-car, are downcycling, since chain scission degrades properties in each case.

Economically, a car is worth far more than a pot, so the public may see the second route as upcycling. The lesson: assigning a direction ascribes value to a process, regardless of what the term would tangibly mean. A recent study on flexible mixed polyolefins reached a similar conclusion, using life cycle assessment to show that a park bench made from film waste is not necessarily downcycling.

The PET bottle: a success story that eats its own feedstock

The authors call bottle-to-bottle PET recycling a genuine success story. A 2022 European market report found that of 5 million tonnes of PET used in packaging, 3 million tonnes were collected, 2.8 million of them bottles. Deposit return schemes (DRS) accounted for about 30% of European bottle collection. The long-established schemes all average over 77% collection: Sweden’s has run since 1984, Norway’s since 1999, Denmark’s since 2002 and Germany’s since 2003. Hungary launched its mandatory deposit return scheme in 2024, and from 2025 PET bottles placed on the Hungarian market must contain at least 25% recycled content.

The paper also gives prices: in Europe, virgin PET costs $1.33 and rPET $1.95 per kilogram. The rPET premium is sustained by recycled-content legislation and corporate green-portfolio goals. Demand for food-contact rPET keeps rising; Asahi, for example, has moved its Australian soft-drink bottles to 100% recycled PET. The same quality, however, attracts other sectors too. Nearly every product marketed as rPET is made from drinks bottles, even though bottle-grade PET has a higher molar mass and intrinsic viscosity than fibre production needs.

The authors warn that diverting bottle PET into textiles cannibalises circularity. Meanwhile thermoformed trays and tubs, textiles and carpets are rarely recycled. These streams could feed fibre production without taking feedstock away from the bottle-to-bottle loop.

PET’s ester linkages also make it a research favourite. After depolymerisation, ethylene glycol and terephthalic acid can be turned into lycopene pigment, adipic acid and even paracetamol, and such routes are often labelled upcycling. Yet, the authors note, economic and environmental impacts are rarely quantified, because waste feedstock is tacitly assumed to be inherently “green”. The volume of waste PET could also quickly swamp the niche markets for these molecules. The paper asks openly whether simply applying the label amounts to greenwashing, intentional or not.

The value of mixtures: a lesson from crude oil

The third case study turns the usual thinking around. A mixture is not automatically a loss of value. Crude oil is one of the most complex mixtures in the world, yet it shaped economies because, over time, valuable uses were found for every component, from fuels to medicines. The authors call this a “mixture of valuable materials”.

They distinguish it from a “valuable mixture of materials”, such as paint: a precise formulation of polymers, pigments, solvents and additives whose value comes precisely from being a mixture. Plastics sit at the intersection of the two. At end of life, they can become either a mixture of valuable materials or a new valuable mixture.

This complicates how chemical recycling should be labelled. Pyrolysis produces carbon black, a liquid oil and gases. In its favour, it fits existing petrochemical infrastructure and tolerates contaminated, mixed feedstock. Against it, it is energy-intensive, and only part of the input becomes products of similar value; the rest goes to fuels (partly to power the pyrolysis itself) or fillers.

A promising direction is tuning polyolefin waste towards waxes, lubricants or surfactants, applications that need mixtures anyway. Still, the authors stress that these products must be shown to meet performance expectations and to have a lower production footprint than the materials they replace. The same yardstick applies to processes turning polyethylene into acetic acid and to every laboratory “upcycling” breakthrough.

Replacing upcycling and downcycling with measurement: LCA and TEA

The paper’s key practical message is that a direction must be demonstrated, not declared. Two increasingly standardised tools exist for this. Life cycle assessment (LCA) measures environmental impacts within defined system boundaries; techno-economic analysis (TEA) maps how costs and revenues are distributed. Ideally the two are used together. The authors also flag LCA pitfalls:

• Different system boundaries: studies are hard to compare with one another.
• Choice of base case: the comparator chosen can skew the result.
• Sensitivity analysis: without it, it is unclear how robust a conclusion is.
• Narrow focus: analysis centred only on carbon footprint can hide other harmful impacts.

Performance and consistency matter just as much. If a recycled material does not perform as intended, diverting the waste stream to it brings none of the hoped-for benefit. Batch-to-batch variation undermines the trust of engineers and buyers alike. The paper points to the automotive sector. An airbag cover in an instrument panel must deform precisely and reproducibly, so it is an open question whether rPP from yoghurt pots is fit for that. For upholstery, perceived quality, feel, colour and smell decide.

The authors also include a “choose your own adventure” decision scheme for PET. The first column lists sources: bottles, thermoforms, textiles, films and multi-material items. The second lists technologies: mechanical recycling with additives or solid-state polymerisation, depolymerisation to monomer, and conversion to other molecules. The third lists value judgements: utility duration, LCA and TEA, feedstock source, application suitability and customer perception. The lesson is that optimising for different criteria makes different routes look best.

Policy, start-ups and environmental justice

In their outlook, the authors describe polymer transitions as a “system of systems”. Technological interventions cannot be judged in isolation, so open data sharing, government action and industrial diversification are all needed.

Policy. The EU end-of-life vehicles directive sets sector-specific goals: 25% of the plastic in a vehicle should be recycled, with a quarter of that coming from automotive sources. This drives recycling within the sector, but the authors call for flexibility to allow cross-sector material flows as well.

Market sizes. The numbers explain why. In 2022, packaging made up 44% of the world’s 391 million tonnes of plastic use, while automotive accounted for 8%, textiles for 14% and building and construction for 18%. In principle, packaging waste could supply the other sectors, provided its quality is adapted. Cross-chain projects such as the InFACT consortium for flexible plastics show what such cooperation can look like in practice.

Innovation. The position of start-ups is fragile. The paper lists several Dutch recycling companies that went bankrupt in 2024, including Blue Cycle, Ioniqa and Fuenix Ecogy. Many failed during scale-up, or because feedstock availability and end-product markets did not match.

Justice. The authors acknowledge that environmental justice was left out of their analysis. If used yoghurt pots suddenly became a valuable feedstock, what would happen to the communities doing the collecting and sorting? Neither Earth A nor Earth B, the paper says, should be allowed to worsen the exploitation the linear economy already causes.

What this means in practice in Hungary

The study deliberately raises more questions than it answers. For Hungarian waste management, it still carries three concrete messages.

Sorting quality is the key to the value chain. In the authors’ words, sorting has to make good decisions: balance volume and throughput against chemical quality and economic value.

Clean material streams need protecting. The uniform bottle stream coming from the deposit return scheme is especially valuable. If other sectors divert it, the bottle-to-bottle loop weakens.

“Upgrading” claims deserve scrutiny. Whether a new technology or a product label promises upcycling, it is fair to ask whether a life cycle assessment, a techno-economic calculation and verified performance stand behind it.

The authors’ closing question is for all of us: next time you finish a yoghurt, where do you want the pot to end up? Another pot, a park bench, a car part? Before sorting any of these into upcycling and downcycling, do we know which economic, environmental and functional data support the decision?

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Frequently asked questions about upcycling and downcycling

What is the difference between upcycling and downcycling?

Upcycling means a quality increase during recycling; downcycling means a quality loss. Under the definition by Helbig and colleagues, quality can change in a thermodynamic, functional or economic sense, and the Manchester authors add an environmental dimension. In practice, though, both terms are often used without measurement, based simply on how the end product is perceived.

Why can the same process be both upcycling and downcycling?

Because the label depends on the point of view from which the process is assessed. When a polypropylene yoghurt pot becomes a car part, its polymer chains break down during processing, so in material terms it is downgraded. Economically, a car is worth far more than a pot, so the public may see it as upcycling. The study argues that assigning a direction is therefore a value judgement, not a fact.

Why is recycling PET bottles into textiles controversial?

Because it diverts high-quality bottle PET into uses that do not need that level of purity. Bottle-grade PET requires a higher molar mass than fibre-grade PET, yet nearly every rPET product is made from drinks bottles. The authors argue this cannibalises bottle-to-bottle circularity, while less-recycled PET streams such as trays, tubs and textiles remain largely unused.

Which tools can verify an upcycling claim?

Life cycle assessment (LCA) and techno-economic analysis (TEA), ideally used together. LCA measures environmental impacts within defined system boundaries, while TEA maps costs and revenues across a process. The study warns that LCAs are hard to compare across studies, that the choice of base case can skew results, and that a narrow focus on carbon footprint can hide other harmful impacts.

Who wrote the study, and where was it published?

The study was written by three University of Manchester researchers: Claire L. Seitzinger, Ciaran W. Lahive and Michael P. Shaver. It is not a University of Cambridge study: it appeared in February 2026 in Cambridge Prisms: Plastics, published by Cambridge University Press, as an open-access perspective article under a CC BY 4.0 licence.

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🔗 Official sources and references: 👉

• Seitzinger, C. L., Lahive, C. W., Shaver, M. P. (2026): Up, down and back again: Value judgements in polymer recycling. Cambridge Prisms: Plastics, 4, e4. https://doi.org/10.1017/plc.2026.10041 – the study on Cambridge Core
• Helbig, C. et al. (2022): A terminology for downcycling. Journal of Industrial Ecology, 26(4). https://doi.org/10.1111/jiec.13289
• Unesda, Natural Mineral Waters Europe, Petcore Europe, Plastics Recyclers Europe (2022): PET market in Europe – State of play

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