The Textile Industry's Recycling Problem Was Always a Design Problem

Mono-material design is often framed as a recycling solution. In practice, it is better understood as something more structural—a design choice that determines whether recycling is even possible, long before a product reaches the end of its useful life.

The technical case is well established. Conventional carpets are typically constructed from multiple layers and materials: cotton yarns, PET fibres, latex-based coatings. The complexity of separating those components makes recycling commercially unworkable, and such products typically end their lives in incineration with energy recovery.

A mono-material carpet, composed of more than 90% polyester, sidesteps that problem entirely. Because the material composition is uniform, the product can be mechanically broken down—shredded, melted, and reformed into new polyester granules—which can then be spun into new fibre suitable for carpet production or broader textile applications.

The researchers built their case study around a carpet production facility in Belgium, producing both a mono-material carpet (MMC) made almost entirely of PET, and a conventional multi-material carpet (CMC) combining cotton, PET, and a latex-based coating. At end-of-life, the two products take very different paths: the MMC goes to a recycling facility in Austria, where it is broken down into polyester granules and then re-spun into new yarn in the Netherlands. The CMC goes to incineration.

The environmental comparison across these pathways is clear. Assessed against the indicators defined by the PEF framework, the recycling scenario for the MMC generally produces lower environmental impacts than direct incineration across most impact categories. That finding holds under both the CFF method and the simpler cut-off approach used in Environmental Product Declarations—a method that attributes all recycling burdens to the product receiving the recycled material, rather than sharing them across the supply chain. It is consistent, the authors note, with the principles of the circular economy and the waste hierarchy.

There is, however, a significant qualification. The environmental advantages of mono-material construction are only realised if the product is actually recycled. If an MMC is incinerated without first going through at least one recycling cycle, its impacts can exceed those of a conventional carpet in several categories, including climate change.

The reason is compositional: producing an MMC from scratch uses more resource-intensive materials than producing a conventional CMC, and without recycling to offset that burden, the mono-material product offers no net advantage. Recyclability by design and recyclability in practice are two different things. The collection infrastructure, the processing route, and the end-of-life pathway all have to function as intended.

What mono-material design actually achieves, then, is to establish the conditions for circularity—building in the material logic that makes closed-loop recovery technically feasible, so that manufacturing, collection, and recycling can align around a common material standard. Whether that alignment occurs depends on factors well beyond the designer's control.

Demonstrating that recycling is better than incineration is relatively straightforward. Defining what counts as circular—and measuring it consistently enough to underpin regulation—is considerably harder. That is the problem the Circular Footprint Formula is designed to address, and where the study's more consequential findings lie.

The CFF is part of the broader Product Environmental Footprint framework developed by the European Commission. Its purpose is to distribute environmental burdens and credits across product lifecycles in a way that reflects both the physical reality of recycling and the economic logic of material markets. In plain terms, it determines how much of the environmental cost—and benefit—of recycling is attributed to the company that produces the recyclable product, versus the company that uses the recycled material. It does this through a set of variables, two of which—factor A and factor B—carry particular weight in determining outcomes.

Factor A governs how those environmental credits are shared between the supplier of recycled material and the product that receives it. It is calibrated to reflect market supply and demand: a low value indicates that demand for recycled material outstrips supply, while a higher value suggests the reverse. In the PEF methodology, the permitted range runs from 0.2 to 0.8.

For the case study, two values were available from the PEF's reference tables—0.5, linked to PET from bottle applications, and 0.8, assigned to textiles on the basis of a T-shirt. Neither fits a recycled-PET carpet, which occupies a distinct and less developed market position.

That gap in the reference tables is not a minor technical inconvenience. The research finds that varying factor A within its permitted range can shift climate change impact results substantially at the individual product level—reaching up to 19% when the energy recovery variable is held at its default, and up to around 30% when an alternative value is applied. For a framework that may become the basis for mandatory environmental declarations in certain sectors, that degree of sensitivity to a variable without a settled value for many textile applications is a material problem.

Two manufacturers assessing functionally identical products could therefore arrive at substantially different results. That divergence is particularly sharp at the individual product level: under the simpler cut-off method, the first product in a recycling chain carries higher impacts than the second; under the CFF, those impacts are more equally distributed—particularly when factor A is set at 0.5, where the two products yield very similar results. Where products in a recycling chain are made by different companies, that difference could directly determine which entity faces higher tax liability or regulatory burden—a consequence the framework does not currently resolve.

Factor B governs the share of environmental credit assigned to energy recovered during incineration. The PEF sets its default value at zero, a position that has attracted criticism on the grounds that it creates an implicit incentive for incineration by assigning the full benefit of energy recovery to the product being burned.

An alternative value of 0.6, derived from Swedish incineration data and calculated separately for Belgium, was tested in the study. The effect on climate change results was up to 6%—meaningful, but substantially smaller than the influence of factor A, and showing up primarily at the level of the overall product system rather than at the level of individual products.

There is a further complication ahead. The PEF methodology is currently being updated to potentially incorporate microplastic shedding as a formally scored impact category. At the time of the study, it was required only as supplementary information, with a disclaimer attached. Should it be fully adopted, overall environmental scores for PET-based products—including mono-material carpets—could shift materially, adding another layer of uncertainty to assessments being made today.

The broader implication is that circularity, as measured within the PEF framework, is shaped as much by how variables are set and how credits are divided as by the physical reality of the recycling process itself. As the framework moves closer to regulatory application, those choices will increasingly determine which products are rewarded, which business models are incentivised, and which material streams attract investment.

The measurement framework sets the rules. Whether those rules translate into functioning circular systems depends on a different set of conditions—ones grounded in material economics, processing capability, and the specific physical characteristics of the fibres involved.

Factor A, as discussed, reflects the commercial maturity of a recycling stream. And for textile-derived recycled PET, the market picture is far more constrained than the PEF reference tables currently acknowledge.

Recycled PET from bottles is a well-established commodity. The collection infrastructure exists, the processing technology is mature, and the material trades at a price that reflects relatively stable supply and demand. Recycled PET from textile fibres—including carpets—occupies a different position entirely.

Supply is limited, the recycling process is more complex and costly, and the recycled material can lose certain performance properties during processing—particularly the structural integrity of the polymer chains, which affects how well it can be re-spun into usable yarn. A supplementary heating process can restore those properties, but it adds cost and energy. The result is a material stream that is scarce, specialised, and not yet part of the kind of liquid secondary market that would allow it to be treated as a straightforward substitute for newly produced PET.

The research points to a factor A value closer to the lower bound of the permitted range—around 0.2—as more reflective of actual market conditions for fibre-to-fibre recycled PET, given limited supply and growing regulatory-driven demand. That is a long way from the 0.8 value assigned to textiles in the current PEF reference tables on the basis of a T-shirt, and the distance between those two figures carries real consequences for how the environmental performance of recycling investments is assessed and communicated.

Yarn thickness adds a further complication. The study examines how this property—measured in units called tex, where a higher number indicates a thicker, coarser yarn—affects energy consumption and environmental outcomes. Finer yarns require considerably more energy to produce than coarser ones, which in turn changes the comparative environmental performance of the product systems being assessed.

In one scenario, using very fine yarns caused the climate change impact of incinerating the conventional carpet to exceed that of incinerating the mono-material carpet without recycling—meaning the conventional product became the higher-impact option, reversing the conclusion that coarser yarn scenarios would otherwise support.

Yarn count, then, is a variable capable of changing the headline result—and the EU's reference datasets do not yet capture that variability with sufficient granularity. The most recent database version defines yarn spinning processes across a limited thickness range and does not cover the coarser yarns used in many commercial carpets. For an industry in which yarn specifications vary enormously across product categories, that gap undermines the precision of any assessment that relies on those datasets. Closing it is a prerequisite for the kind of consistent, comparable environmental reporting that the PEF framework is designed to deliver.

The Work Still Ahead

Mono-material design is a credible step towards making textile circularity technically viable—but the study makes clear that design alone is not sufficient. The measurement standards that will govern how circularity is defined and rewarded are still being refined. The datasets needed to assess it accurately are still being built. And the markets for recycled textile fibre are still finding their footing. Until those three elements mature in step with the products designed around them, recyclability will remain more promise than practice.