polymerjournals Chemistry, materials, technology
Progress in Rubber, Plastics and Recycling Technology

Enzymatic PET recycling moves closer to full-scale industry

April 1, 2026 By: Carbios
PET recycling bioreactor plastic bottles
Image source: Shutterstock / Ground Picture

One of the most closely watched ideas in plastics recycling is no longer just a laboratory story. Carbios, the French company developing enzymatic recycling for polyethylene terephthalate, or PET, has helped move the field from academic proof of concept toward industrial deployment. That matters because PET is one of the world’s most important packaging plastics, but it is also one of the clearest examples of the gap between what is technically recyclable and what is actually recovered at high value.

For years, the standard route for used PET bottles has been mechanical recycling. That approach can work well when waste streams are clean, sorted and relatively simple. In the real world, though, PET often arrives mixed with labels, colors, multilayer structures, additives, trays, food residue and other contamination. Mechanical recycling can also shorten polymer chains and reduce material quality over repeated cycles. The result is that much PET is still downcycled, exported, burned, or landfilled instead of being turned back into bottle-grade material.

Carbios is betting that enzymes can change that equation. Rather than melt and remold the polymer, the company’s process uses an engineered enzyme to cut PET back into its building blocks. Those monomers can then be purified and used to make new PET with properties comparable to virgin resin. In simple terms, the goal is not just to recycle plastic, but to chemically reset it.

The technology has drawn sustained attention because it sits at the intersection of polymer chemistry, biotechnology, process engineering and circular-economy policy. It also addresses a practical market need. Brand owners want recycled content, regulators increasingly demand it and converters want a route that can deliver consistent, food-contact-quality raw material from difficult waste streams.

Why PET is such an important target

PET is used widely in drink bottles, food trays, thermoforms, films and textile fibers. It is popular because it is light, strong, transparent and easy to process. Chemically, it is a polyester made from terephthalic acid and ethylene glycol. That ester chemistry is important, because ester bonds are much easier to break selectively than the carbon-carbon backbones found in plastics such as polyethylene and polypropylene.

That makes PET one of the most realistic candidates for advanced depolymerization. If the polymer chains can be broken cleanly into monomers, those monomers can be purified and used again in conventional PET production. In principle, that means a used bottle, tray, or polyester-rich waste stream could become feedstock for another high-performance product instead of losing value with each cycle.

There is also a strategic reason to focus on PET. Mechanical recycling infrastructure already exists for part of the market, especially clear bottles, so enzymatic recycling does not need to replace everything. Instead, it can target fractions that are currently difficult to handle, such as colored PET, opaque items, complex packaging formats and certain textile-rich or tray-rich streams. That complementary role is important. The best recycling systems are rarely based on one technology alone.

How the enzymatic process works

The basic idea is elegant, even if the industrial reality is not simple. PET waste is first collected, sorted, cleaned and reduced to small flakes. The material is then fed into a reactor where an engineered enzyme attacks the ester bonds in the polymer. Under controlled conditions of temperature, pH, mixing and residence time, the long PET chains are broken down into smaller molecules and, ultimately, into the original monomers or monomer-like intermediates that can be converted back to terephthalic acid and ethylene glycol.

After depolymerization, the process separates and purifies the recovered chemical building blocks. These purified inputs can then go into standard polymerization equipment to make new PET resin. Because the polymer is rebuilt from clean monomers rather than simply remelted from old chains, the final resin can reach a much higher and more predictable quality level.

This is the core claim behind “infinite recycling” language often used around depolymerization. The chemistry can, in theory, support repeated cycles without the cumulative chain damage seen in purely mechanical routes. In practice, of course, every real process still has losses, energy inputs, contamination limits and economics to manage. But the scientific logic is sound.

  • Step 1: collect and sort PET-rich waste streams
  • Step 2: wash, shred and prepare the feedstock
  • Step 3: depolymerize PET in water using an engineered enzyme
  • Step 4: remove dyes, additives, labels and other impurities
  • Step 5: recover purified terephthalic acid and ethylene glycol
  • Step 6: repolymerize those building blocks into new PET

For polymer scientists, the attraction is obvious. The process takes advantage of PET’s chemical structure rather than fighting against it. For industry, the key question is whether that selectivity can be maintained at large scale, with mixed real-world waste, at a cost that makes commercial sense.

Why enzymes are getting serious industrial attention

Enzymes bring several advantages to depolymerization. They are selective. They work in water-based systems. They can operate under milder conditions than some thermochemical alternatives. And because they are catalysts, only relatively small amounts are needed if they are stable and productive enough. That combination is appealing in a recycling field where high temperatures, high solvent loads, or poor selectivity can quickly undermine both cost and sustainability claims.

Carbios’ work is built on the idea that natural enzymes can be improved for industrial use. In nature, enzymes that attack polyester-like materials are not optimized to chew through large volumes of post-consumer PET. Through protein engineering, researchers can improve heat tolerance, activity and stability so that the catalyst performs in a reactor rather than only in a biological niche. That is one of the most important scientific shifts behind the current progress.

Another reason for the industrial interest is product quality. If depolymerization and purification are effective, the recycled monomers can be used to produce resin suitable for demanding applications. That is particularly valuable for food and beverage packaging, where consistency, safety and regulatory compliance matter. Mechanical recycling remains essential, but it can be harder to maintain top-grade quality when the input stream is highly variable.

Brand owners have noticed. Beverage, cosmetics and consumer-goods companies have shown interest in advanced PET recycling because it offers a possible route to recycled content without sacrificing clarity, strength, or food-contact performance. That does not guarantee economic success, but it does mean there is real market pull.

What makes scale-up difficult

The jump from a good paper or pilot line to a full plant is where many recycling technologies struggle. Enzymatic PET recycling is no exception. The chemistry may be selective, but the incoming waste stream is not. Industrial success depends on several linked issues: feedstock quality, pretreatment, reactor design, catalyst cost, impurity removal, water handling, energy use and downstream monomer purification.

Feedstock preparation is especially important. PET in bottles, trays and textiles does not behave in exactly the same way. Crystallinity, wall thickness, colorants, barrier layers and additives all affect how easily the polymer can be attacked. High crystallinity can slow depolymerization, so the polymer may need thermal or mechanical pretreatment that makes the chains more accessible to the enzyme. That adds cost and process complexity.

There is also the contamination issue. Labels, caps, adhesives, inks and residues do not disappear just because the main polymer is being enzymatically cut. The process must either tolerate those materials or remove them effectively. That is one reason advanced recycling plants still depend on good sorting systems. The cleaner the input, the better the output and the economics.

Enzyme performance itself is another challenge. Catalysts used in industry need more than high activity in a lab assay. They must stay active long enough, withstand real processing conditions and work reproducibly from batch to batch. They also have to be manufactured at a price that fits the business case. Biotechnology can deliver impressive catalyst performance, but cost and robustness often decide whether a process survives.

Then there is plant integration. Recovered monomers must meet strict specifications if they are going back into PET production. That means purification cannot be an afterthought. Removing color bodies, trace additives and degradation products is central to the value proposition. A recycling technology that makes impure monomers is not solving the full problem.

Where enzymatic recycling fits in the wider plastics system

It is important not to oversell the technology. Enzymatic recycling is not a universal answer for all plastics. It is especially relevant to polyesters and PET is the clearest early target. It does not solve the challenge of mixed polyolefins. It does not remove the need for waste reduction, reuse systems, better package design, or improved collection infrastructure. And it does not make every difficult PET article instantly recyclable at low cost.

But it does offer something valuable: a route for recovering high-value material from waste that today often falls outside the best mechanical streams. In that sense, the technology may be most powerful when used as part of a layered recycling system.

  • Mechanical recycling remains the best first option for clean, well-sorted PET where quality can be preserved efficiently.
  • Enzymatic depolymerization can serve harder fractions where monomer recovery has an advantage.
  • Design for recycling can make both routes work better by reducing problematic additives, multilayers and labels.
  • Collection and sorting upgrades determine whether enough suitable feedstock reaches any plant at all.

This systems view matters because advanced recycling debates often become polarized. Supporters sometimes present chemical or enzymatic routes as transformational solutions. Critics sometimes dismiss them as expensive distractions. The reality is more technical. A process should be judged by where it works, what material it displaces, what waste it can actually accept and whether the energy and economics hold up outside pilot conditions.

Textiles could be a major long-term opportunity

Although bottle and tray applications get most of the public attention, textiles may become an even larger long-term opportunity. Polyester fibers represent a vast PET reservoir, but textile recycling is much harder than bottle recycling because fabrics are blended, dyed, finished and assembled into complex products. Separating polyester from cotton, elastane, or other fibers is a major challenge.

Enzymatic PET depolymerization could become a useful tool in that area if upstream sorting and separation improve. A process that can recover PET chemistry from textile waste without simply shredding it into lower-grade fiber would be attractive. The challenge is that textile feedstocks are usually far dirtier and more heterogeneous than bottle flakes. Any claim of large-scale textile circularity will depend on preprocessing technology as much as on the enzyme itself.

Even so, the possibility is significant. Packaging markets are already under pressure to improve recycling, but textiles remain a largely open frontier. If enzymatic routes prove robust there, the impact on polyester circularity could be substantial.

What to watch next

The next phase is less about whether the chemistry works and more about whether industry can make it routine. Several questions will define the field over the next few years.

First, can industrial plants operate steadily on real feedstock rather than idealized material? Continuous or near-continuous performance, not isolated demonstration runs, will matter most. Second, can the process deliver competitive economics once collection, washing, pretreatment, utilities, purification and capital costs are all counted? Third, can life-cycle assessments show clear environmental benefits compared with virgin PET and with strong mechanical recycling routes? And fourth, can enough suitable PET waste be secured through supply contracts and municipal systems?

Policy will also shape the answer. Recycled-content mandates, extended producer responsibility systems, landfill restrictions and packaging rules all influence whether advanced recycling capacity gets built. When brand owners are required to include more recycled content, high-quality monomer routes become more valuable. On the other hand, if regulations demand strong proof of environmental performance, developers will need transparent data rather than broad circularity claims.

That is why Carbios’ progress is being watched far beyond one company. The story is not only about a single process. It is about whether polymer recycling can move from damage control toward true material recovery in at least some product categories.

A measured but important step forward

Enzymatic PET recycling should not be treated as magic, but it should be taken seriously. The science is credible, the industrial rationale is clear and the market need is real. The main remaining questions are those that always matter in industrial polymer technology: scale, cost, reliability, feedstock and integration.

If the process performs as hoped at commercial scale, it could help close one of the most persistent loops in plastics packaging by turning lower-value PET waste back into high-value monomers for new resin. That would not eliminate the need for better product design or stronger collection systems, but it would give the circular economy something it often lacks: a technically elegant solution that can also plug into existing polymer manufacturing.

For now, the significance of Carbios’ work is straightforward. It shows that advanced polymer recycling is no longer confined to abstract concepts or small academic experiments. A real industrial attempt is under way to use biology-inspired catalysis to rebuild one of the world’s most common plastics from the inside out. In recycling, that is a meaningful shift.

Source organization: Carbios

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