What Is PET Depolymerization?
PET depolymerization – also called chemical recycling or molecular recycling – is the treatment of polyester terephthalate (PET) waste with a chemical reaction and moderate heat to produce chemical precursors (monomers) of PET. It’s the most promising end-of-life solution for contaminated PET waste streams and will be essential for meeting the multitude of impending recycled content requirements for PET beverage bottles.
Background:
Leading PET depolymerization developers have reached an appreciable demonstration scale, but low-quality PET waste availability is limiting commercial viability; current efforts primarily focus on expanding the scope of potential waste feedstocks. The success of developing low-quality PET waste supply chains will determine how the technology is commercialized – through economies of multiples or economies of scale – and who owns it – corporate polymer manufacturers or small-to-medium enterprises (SMEs) and traditional waste management companies.
PET depolymerization developers have a major variation in the type of chemical reaction performed and several smaller variations in what they use to accelerate that reaction. Based on the type of chemical reaction used, we segment the PET depolymerization landscape into three categories: hydrolysis, methanolysis, and glycolysis. Participants span the globe (Americas, EMEA, and Asia-Pacific) and consist mainly of SMEs and research institutions, though corporates are starting to become more involved through both internal technology developments and joint ventures.
To provide a comprehensive overview of this landscape, we leveraged various Lux data tools alongside our existing coverage to compile a list of relevant organizations. This information serves to define key trends and identify opportunities for those seeking to engage and enter the market.
The Americas and Emea Dominate Corporate & Sme Activity, but Apac Sees a Growing Share of Research Institutions.
A decade ago, PET depolymerization was most popular in Asia-Pacific (mostly China), involving developers like Toray, M&G Chemicals, and Zhejiang Jiaren New Materials; however, setbacks from low impurity tolerance and waste generation stymied success. Today, most commercialization efforts are taking place in the Americas and EMEA, though research in Asia-Pacific, especially around hydrolysis-based processes, has regrown substantially in recent years. Most of this research is focused on developing and improving the functionality of catalysts. While hydrolysis dominates overall research activity thanks to efforts in Asia-Pacific, commercialization efforts are spread relatively evenly among the three technology approaches.
Development Focus Has Shifted Toward Expanding the Scope of Viable Waste Feedstocks to Support Large-scale Operations.
Leading PET depolymerization developers have demonstrated that the technology can process heavily contaminated PET waste in a relatively short amount of time (less than six hours) while producing high-purity monomers but have relied on niche low-quality PET waste sources like polyester carpeting waste to supply the process. In 2019, industry sentiment expected PET depolymerization to continue relying on a short list of locally available waste streams, resulting in distributed, rather than large-scale, expansions; however, recent activity indicates that PET depolymerization may be able to tap into packaging and (more importantly) textile waste, enabling 100,000+ tpa operations. The barrier to using textile waste is contamination with polycondensate (nylon), one of the only materials that can disrupt PET depolymerization, which is extremely difficult to identify through manual sorting. While it is technically possible to develop a process, such as Ioniqa’s, that can accept a large amount polycondensate contamination, most developers will rely on an advanced pretreatment process, likely utilizing automated sorting equipment.
If Commercial-scale Operations Are Possible, Development Will Shift Toward an Economies of Scale Approach.
If the several impending 100,000+ tpa expansions are successful, we will likely see large companies with synergistic downstream assets (PET manufacturers) begin acquiring PET depolymerization technology assets through licensing and joint venture agreements and dominate scale-up. By utilizing their superior assets to scale up rapidly, they will outpace SMEs pursuing build, own, operate (BOO) business and force them to change strategies, a similar dynamic to what is currently playing out in plastic pyrolysis. If so, these companies will look to identify locations with access to low-quality PET waste (or a strong transportation network), existing PET manufacturing assets that align with the depolymerization products, and strong local government support.
Hydrolysis:
The former most popular depolymerization route, hydrolysis utilizes sodium hydroxide and water to induce a redox reaction in PET, breaking it into terephthalic acid (TPA) and (mono)ethylene glycol (MEG) monomers. TPA and MEG are the most common monomers for modern-day PET production, enabling hydrolysis developers to sell their products into the open market. Hydrolysis tends to produce more hazardous wastewater than the other routes, which is the reason for its declining popularity. Certain developers, such as Gr3n Recycling, claim they can recycle fluids several times, but others, such as Loop Industries, have found significantly more success after switching the reaction type.
Methanolysis:
The least popular but perhaps most promising depolymerization route, methanolysis utilizes methanol to induce a transesterification reaction in PET, breaking it into dimethyl terephthalate (DMT) and MEG monomers. The PET industry has shifted away from DMT toward TPA over the past decade due to processing and environmental advantages, though a minority of facilities still use a DMT-based process, typically forcing developers to secure downstream off-take agreements with the right type of PET manufacturer. Methanolysis typically does not produce hazardous wastewater, though methanol must be recovered with high efficiency for economically viable operations.
Glycolysis:
The most popular depolymerization route, glycolysis utilizes MEG to induce a transesterification reaction in PET, breaking it into a bis(2-hydroxyethyl) terephthalate (BHET) monomer. BHET is a chemical intermediate formed partway through PET resin production and, after process modification, can be added directly to this step of PET production; adding water to BHET produces TPA and MEG. BHET can be added partway through either TPA- or DMT-based PET manufacturing but is not used directly by any PET manufacturers, forcing developers to secure downstream off-take agreements with PET manufacturers willing to modify their process.
#LuxTake:
The need for food-grade recycled PET is driving significant consumer packaged goods interest in and funding for PET depolymerization processes. While many PET manufacturers have off-take agreements with depolymerization developers, their level of ownership is largely dependent on the success of impending large-scale expansions. Regardless of who ultimately owns the depolymerization technology, we expect the technology to find long-term success.
The availability of waste, synergies with existing assets, and local government support are all needed to support large-scale PET depolymerization operations. While the technology certainly does not fit all circumstances, such as plastic pyrolysis, development is nascent enough to warrant exploration by manufacturing clients with these synergies. Companies should monitor ongoing scale-up efforts as key indicators of depolymerization’s large-scale viability.