Today CHEM Trust publishes a detailed report on ‘Chemical Recycling’, a set of technologies that are often claimed to be on the cusp of revolutionising the recycling of plastics. This study finds that these technologies in reality have major problems, including substantial energy use, a need for pre-sorted, good quality plastic input and concerns over hazardous chemicals.
The report, “Chemical Recycling: State of Play“, written by the environmental consultancy Eunomia, reviews available information on a large number of different chemical recycling technologies, and attempts to assess their performance and feasibility, including their energy use, climate impacts, to what extent they are able to address hazardous chemicals and how they might fit into waste management systems.
Eunomia identify a lack of adequate information as a pervasive problem when assessing these technologies. However, with the information available they assess that some chemical recycling technologies perform better than others. All technologies share key issues including energy use, need for almost clean and homogeneous inputs, and problems competing with mechanical recycling technologies.
Many of the technologies are not able to deal fully with hazardous chemicals in the plastic feedstock, generate waste that may contain hazardous chemicals, and it is often hard to establish to what extent hazardous substances are used within (or generated by) the chemical recycling processes.
What is chemical recycling?
Chemical recycling aims to recycle plastics by changing their material structure. There are three broad categories of chemical recycling, which are suitable for different types of plastics. In brief:
- Solvent purification, where the plastic is dissolved in a solvent in order to separate it from other contaminating materials. This approach has been used with polystyrene.
- Chemical depolymerisation, where the plastic polymer chain is broken down into smaller units through the use of chemicals which split it into the original monomers. These monomers can be purified and then used to make new plastic polymers. This approach has been used with PET/polyester and a number of similar polymers.
- Thermal depolymerisation, where the plastic polymer is broken into smaller units using a heat treatment, often pyrolysis (heating with limited oxygen). The resultant pyrolysis oil is a mixture of chemicals, which can be purified and used as a feedstock in polymer production, for example being used to replace some of the oil-derived naphtha that goes into a standard petrochemical steam cracker. This approach is generally used for polyolefin plastics like polyethylene and polypropylene. In some plants the pyrolysis oil is burnt rather than used for creating new polymers, but it is important to note that burning the oil is not recycling under EU law.
How the report assesses the performance of chemical recycling
The important factors when assessing the performance of chemical recycling, which are covered in-depth in the full report, include:
- Input material type – can mixed plastic waste be processed, or does it need to be pre-sorted?
- Energy use in both the recycling and purification processes, and the climate change impacts
- Fate of any hazardous chemicals in the input material
- Use or generation of any hazardous chemicals within the process, and where these chemicals end up, for example in a waste stream
- How much of the input material is actually recycled
- Comparison with the performance and cost of normal material recycling
- What is a reasonable estimate of the recycled content of the polymer output?
- This is particularly important when implementing EU targets for recycled content of plastics; Eunomia is a contractor on a European Commission study on this issue.
The full report uses Eunomia’s information on a very large number of different technologies to assess these factors; the full list of technologies is listed in Annex A.
The table at the bottom of this blog page summarises some key outcomes of the Eunomia analysis; the table can also be downloaded as part of the Executive Summary (though this should be read in association with the full report).
Does chemical recycling address hazardous chemicals in the circular economy?
The CHEM Trust position for many years has been that a sustainable circular economy is a clean circular economy, one that doesn’t perpetuate the use of hazardous chemicals and where hazardous chemicals are not allowed to be stuck in the recycling loop. In our opinion, the question for chemical recycling is whether this technology fits into a ‘clean circular economy’?
The EU chemical industry trade association CEFIC has claimed that chemical recycling has the potential “to capture and separate the so-called legacy chemicals and substances of very high concern (SVHC) that can be present in end-of-life plastic”. The Eunomia study finds that the situation is rather more complex than this.
Importantly, the report finds that there is a lack of information concerning:
- the nature, quantity and toxicity of the solvents, chemical reagents and catalysts used;
- the nature and fate of the wastes and by-products formed and separated during the process.
Bearing this general lack of information in mind, the report identifies specific issues with the three types of technology:
- Solvent purification: This is a technology which has been specifically used to (at least partially) remove hazardous chemicals from waste plastics. Here are two relevant examples of solvent purification processes:
- The VinyLoop technology, developed by Solvay, which processes PVC waste. A plant was constructed and was economically viable until the tightening of the REACH regulation regarding phthalates, plasticisers used to soften PVC. The operator closed the plant in 2018 after fifteen years of operation as it was not economically feasible to separate phthalates with the VinyLoop process to the extent necessary to comply with new regulations.
- The PolyStyreneLoop technology, which is at a pilot stage, and is being used to recycle foamed polystyrene from industrial insulation waste which is contaminated by the brominated flame retardant Hexabromocyclododecane (HBCD). The company reports that most (though not all) of the HBCD is removed from the output polystyrene.
- Chemical depolymerisation: This technology can produce virgin-equivalent plastic after the purification of the monomers. However, Eunomia find that there is a “general lack of understanding around the level of contamination that the technologies can handle, nor how the contaminants are dealt with following monomer purification”.
- Thermal depolymerisation: This technology can also produce virgin-equivalent polymers from the final cracker output. However, pyrolysis itself produces a complex mix of chemicals and can lead to the formation of toxic by-products such as dioxin, polycyclic aromatic hydrocarbons and hydrogen chloride. The pyrolysis oil must therefore be purified (and diluted) prior to being used in the cracker, and this purification stage will require further chemicals and will generate wastes that are likely to be hazardous – it will also have energy and financial costs.
A need for transparency
The key conclusion that Eunomia draws in the report is the need for greater transparency on the performance of these technologies, here is an extract:
“Throughout this report the overriding finding is that there is a general lack of transparency or robust evidence base that can be used to verify claims or generate firm conclusions around the viability of many technologies….This also means that caution must be exercised as a lack of evidence can mean either a knowledge gap or that the answer is less favourable.
In the interests of confirming the role, scale and scope of these technologies, there is an urgent need for more transparency within the chemical recycling industry. There is evidence to indicate that at least some technologies have promise, but important details around mass flows, chemical use and the viability of the processes in real-life waste management circumstances are largely incomplete. Investment should be reserved for those organisations that freely engage to improve the understanding around these missing elements.” [our emphasis]
CHEM Trust’s view
Dr Michael Warhurst, Executive Director of CHEM Trust said:
“CHEM Trust commissioned this report to try to find the truth behind the hype about chemical recycling.
In the context of a clean and safe circular economy, as advocated by CHEM Trust, it appears that chemical recycling is being oversold. Decontamination of the recycling stream with these technologies requires extensive sorting and pre-treatment, and high energy input. The end result may still be contaminated with hazardous chemicals, and the economic viability of many of these technologies is in doubt.
CHEM Trust is also concerned about a lack of available information regarding the use, generation and fate of hazardous substances in these processes.
CHEM Trust’s view remains that the best way to achieve clean circular economy is to phase out the use of the most hazardous substances and ensure that they are not recirculated in secondary materials.
The ‘Chemical Recycling: State of Play’ report covers many aspects of chemical recycling, including the important and controversial issue how to calculate recycling rates. We hope that the report will help others in understanding the different aspects of the performance of chemical recycling technology”
For more information, see the full “Chemical Recycling: State of Play” report; you can also download the Executive Summary (though this should be read in association with the full report).
- This report has been quoted and used for identification of a ‘start set of papers’ in an RPA report for the European Chemical Agency ECHA, “Chemical Recycling of Polymeric Materials from Waste in the Circular Economy‘, published in November 2021.
- This report has been cited in Zero Waste Europe’s report “Understanding the Environmental Impacts of Chemical Recycling: Ten concerns with existing life cycle assessments“.
- The launch of this report has been covered by Food Packaging Forum and by Politico Sustainability Pro.
