The chemical reality of recycled polyester, can circular fashion be truly clean?

In a world drowning in textile waste, recycled polyester has emerged as a beacon of hope for a circular economy in the fashion industry. Yet, as companies and policymakers push for more ambitious recycling targets, a critical question looms: Is recycling truly clean, or are we just moving chemical contamination from one product to the next? The answer lies in the complex and often overlooked world of chemical recycling.

The global market for recycled polyester filament yarn was valued at approximately $5.5 billion in 2023 and is projected to grow to $9 billion by 2030, pushed up by consumer demand for sustainable clothing. While this growth is encouraging, the sustainability of the process itself is now under scrutiny. The recycling of polyester, a process known as polyethylene terephthalate (PET) recycling can be achieved through two main methods viz mechanical and chemical.

Mechanical recycling is the more established method, involving the collection, cleaning, shredding, and melting of PET waste (like plastic bottles or old garments) into new fibers. It is a straightforward process but has significant limitations. Contaminants from the original materials, such as dyes, finishes, or heavy metals, can persist in the final product. A study led by major brands like H&M and IKEA found that in samples of shredded polyester, only 10 per cent contained no detectable hazardous substances, with half containing at least one substance above industry-restricted limits.

Chemical recycling breaks the polyester down into its original monomers through a process called depolymerization. This involves using heat, solvents, and catalysts to reduce the polymer to its chemical building blocks (monomers) before they are re-polymerized into new, virgin-like quality material. This chemical breakdown is the key to creating a truly clean, closed-loop system, but it is not without its own set of chemical realities.

Challenges with chemical recycling

The depolymerization process requires a variety of chemical inputs, depending on the chosen method. These inputs, while necessary, must be tightly managed to prevent new contamination.

The real value of chemical recycling lies in its ability to purify the material. However, if not properly managed, this process can release or leave behind hazardous substances. These include solvents and Volatile Organic Compounds (VOCs), catalyst residues, and lingering contaminants from the original feedstock like PFAS, phthalates, and flame retardants. Without advanced purification systems, these substances can pose a risk to workers, the environment, and consumers.

How the processes work

Glycolysis: This method uses ethylene glycol to break down polymers, especially polyethylene terephthalate (PET). It's a type of alcoholysis that's effective for PET recycling, creating monomers that can be used to make new polyester. It's often carried out at relatively mild temperatures and pressures with catalysts like zinc acetate.

Methanolysis: This process uses methanol to depolymerize PET under high pressure and temperature. The output is monomers that can be purified and re-used. While this is an effective method, it can be costly and requires significant energy, with the corrosive nature of methanol posing challenges for industrial equipment.

Hydrolysis: This process uses water and either a strong acid (like sulfuric acid) or a strong base (like caustic soda) to break down textile polymers. Acid hydrolysis is particularly effective for cotton (cellulose), while alkaline hydrolysis works well for polyester. This method can be energy-intensive and may produce hazardous byproducts that require careful management.

Enzymatic recycling: Considered a more sustainable option, this process uses specific enzymes to selectively break down polymers like PET. Enzymes are biological catalysts that work under milder conditions (lower temperatures and pressures), making the process less energy-intensive. It can effectively handle mixed and contaminated textile waste, and the resulting monomers are of high quality. While promising, this is a newer technology that still faces challenges with cost-effectiveness and scalability for industrial use.

Regulatory Imperatives and Industry Case Studies

The need for robust, chemically safe recycling is no longer just a brand's choice—it is a regulatory mandate. Policymakers are introducing new laws to force the textile industry to take responsibility for its waste and the chemicals it uses.

The European Ecodesign for Sustainable Products Regulation (ESPR), approved in May 2024, is set to be a game-changer. It will introduce a Digital Product Passport (DPP) for textiles, requiring detailed information on a product's composition, durability, and recyclability. The regulation also aims to ban the destruction of unsold consumer products, prioritizing reuse and recycling. The ESPR will compel brands to use recycled content and avoid substances that hinder circularity.

Similarly, in the US, California's Senate Bill 707 (SB 707), also known as the Responsible Textile Recovery Act of 2024, establishes the nation's first Extended Producer Responsibility (EPR) program for textiles. This law makes producers accountable for the end-of-life management of their products by requiring them to fund and manage statewide collection, sorting, and recycling programs. By 2030, the law mandates a comprehensive system for textile recovery, including provisions to manage chemical contaminants like PFAS to prevent them from entering the recycling stream.

Companies take the lead

Several companies and consortia are pioneering textile-to-textile recycling solutions. One notable example is the industry study led by major brands, which highlighted the prevalence of restricted chemicals in pre-consumer textile waste. Their findings underscore the urgent need for recycling processes with advanced purification capabilities. The study, which tested samples of shredded polyester, found that the most frequently detected hazardous substances were polycyclic aromatic hydrocarbons (PAHs) and nickel, with a high number of samples exceeding safe limits for banned substances like nonylphenol (NPEO), BPA, and phthalate DEHP.

These examples and regulatory drivers illustrate a clear path forward. The future of fashion’s circularity depends not just on the ability to turn old textiles into new ones, but on a commitment to a new standard of chemical management one that ensures a clean start for every recycled fiber.