(Translated with MistralAI without further editing)

With highly active enzymes, the startup Ester Biotech transforms hard-to-recycle polyester waste into high-quality recyclates, creating a closed loop for PET and other polymers. In this Hotseat Interview, co-founder Martin Hirschfeld explains how this works and why the approach is more cost-effective and sustainable than conventional methods.

Hello Martin, you officially founded Ester Biotech last year. Can you describe your idea and where you currently stand?

Our goal is to use enzymes to make a decisive contribution to solving the global plastic crisis. To this end, we are developing biocatalytic processes that can convert previously hard-to-recycle polyester waste into high-quality recyclates.

Our enzymes specifically cleave the ester bonds in polyesters like PET, allowing the original monomers to be recovered, purified, and reused for the synthesis of new polymers. This produces recyclate that is also suitable for applications with particularly high quality requirements, such as food packaging, cosmetics, pharmaceuticals, textiles, or technical applications.

Scaling is taking place for both the recycling process and enzyme production, each with strong strategic partners, so that both paths can be built efficiently. The recycling process currently operates on a 100-liter scale, and in parallel, we are validating the material quality together with a global PET manufacturer. Our goal is to reach TRL 6 in the coming months, a decisive step toward industrial implementation.

What actually distinguishes your enzymes and your process from the process developed by the French company Carbios for enzymatic PET recycling?

Our enzymes are characterized by exceptional activity and stability in polyester degradation, forming the key to a cost-effective process with the highest recyclate quality. Compared to competitors like Carbios, we achieve a reduction in process costs through better enzyme performance.

The foundation for this is our proprietary enzyme development framework: Our patented screening system works with real plastic films, allowing us to test and optimize enzymes directly on actual plastic surfaces. Plastic degradation is tracked in high throughput, almost in real time. We use this data for machine learning, which accelerates and targets development more effectively.

Building on this, our further focus is on a lean and circular process design. For example, we can use PET thermoform flakes directly from the shredder without energy-intensive extrusion pretreatment. At the same time, we have evolved our processes from classic batch reactions toward fed-batch and, in the future, continuous operation modes, significantly optimizing feedstock costs, energy efficiency, and throughput.

Looking ahead, we are consciously thinking beyond PET. Bio-based plastics contain valuable chemical building blocks that are too precious to simply compost or incinerate. Our goal is to develop enzymatic recycling solutions for these materials as well, keeping their building blocks consistently in the loop.

For plastic recycling, there are already well-established mechanical processes and other raw material recycling approaches, such as pyrolysis. Where do you see the advantages of enzymatic processes like yours?

Mechanical recycling remains a very important pillar. Our enzymatic approach is therefore not intended as a replacement but as a targeted complement for plastic streams that can no longer be meaningfully recycled mechanically. Chain breaks, accumulation of additives, and foreign substances—mechanical recycling has its limits, and thermal recovery usually follows. This is where we come in: With our ESTER Upcycle process, we break down such materials back into their chemical building blocks, enabling the production of new, high-quality plastic. This way, the carbon contained can be kept in the loop for longer.

Compared to other raw material recycling processes, I see several specific advantages in the enzymatic approach.

First, the high selectivity and robustness of the enzymes enable reliable depolymerization even of heavily contaminated waste without producing unwanted byproducts. This ensures stable yields and simplifies downstream processing.

Second, depolymerization occurs under mild conditions at around 65°C without pressurization. This allows the process to be operated with high energy flexibility, for example by using waste heat or integrating renewable energy sources, improving energy efficiency and optimizing the CO₂ footprint.

Third, recycling at the monomer level offers both technical and regulatory advantages. The closed loop can be achieved with relatively few process steps, reducing costs and CO₂ emissions. At the same time, current EU drafts on mass balance for recyclate quotas provide for the so-called “fuel-use-excluded” approach. Our process benefits from this, as the output is fully credited toward the recyclate quota, whereas some other processes may not be able to do this in the future.

Based on these factors, I see great potential for our enzymatic approach to help the industry meet increasing recycling and recyclate quotas—especially for applications with high quality requirements. Compared to other raw material recycling processes, we expect our process to be competitive in terms of both cost and CO₂ emissions. At the same time, it opens up better opportunities for decentralized plant concepts and generally enjoys high societal acceptance. Our preliminary techno-economic analysis and a life cycle assessment for an industrial-scale plant with a capacity of 45 kt of plastic waste per year confirm this assessment and encourage us and our partners to consistently scale the process further.

In addition to recycling packaging, there are other applications where polyesters are used. Where do you see interesting opportunities for ESTER Biotech? Are you looking for cooperation partners for joint development projects?

We want to support the bio-based plastics industry in developing new types of polymers that are designed according to the circular-by-design principle from the outset. Building on this, we can implement cost-effective, circular recycling solutions based on our experience with PET recycling.

The excellent properties of our enzymes in polyester degradation and modification, combined with the development framework to adapt them specifically for particular applications, open up numerous other potential fields of application. We are currently evaluating these intensively with various industrial partners and conducting feasibility studies.

Since we assume that not all potential has yet been identified, we welcome exchanges with interested industry and research partners. Whenever it comes to specifically breaking down, separating, or modifying the surface of polyesters (such as increasing hydrophilization, improving homogeneity, or roughening), we are happy to act as a competent and cooperative partner.

You recently joined the Chemie-Cluster Bayern. What makes our network so valuable to you?

Joining the Chemie-Cluster Bayern gives us access to a strong network of industry, research, and technology partners, creating the foundation for targeted knowledge exchange and new strategic collaborations.

The first meeting at a trade fair and the subsequent online meeting with an extended group showed that there is an excellent fit both personally and professionally. At that time, we began to focus more intensively on additional applications for our enzymes. We were looking for a broad industrial network that is also firmly rooted in biotechnology and chemistry—and we found it in the Chemie-Cluster Bayern.

The network enables us to contribute our expertise, learn from the experiences of others, and jointly develop innovative solutions for the challenges in the plastic circular economy.

About Martin Hirschfeld

As Co-CEO and co-founder, I am primarily active in the areas of finance, corporate and business development, sales, and project management. I studied industrial engineering and management and am passionate about working interdisciplinarily. What particularly motivates me is the ability to quickly and intensively familiarize myself with new fields.
Before joining ESTER Biotech, I worked for nearly ten years as a quality manager across various industries and company sizes—from startups to mid-sized companies and large corporations.