Recycling Efficiency:
Recycling Efficiency: Over 85 % of the mass of plastic converted to hydrocarbon product Advantages: High conversion efficiency, the technology is scalable, controllable reaction, process flexibility, and does not generate toxic products. Disadvantages: Does not mention specifically thermoset materials Case study ReNew ELP is the first commercial-scale HydroPRS site, already under construction, with an annual capacity of 80,000 tonnes on completion. Companies: ReNew ELP Location: Teesside, North East England Input material: End-of-life plastic Output material: Naphtha, distillate gas oil, heavy gas oil, heavy wax residue Objective: Recycle all kinds of plastics Methods: N/A Results: N/A Additional information: HydroPRS process breaks down the long-chain hydrocarbons and donates hydrogen to produce shorterchain, stable hydrocarbon products for sale to the petrochemical industry for use in the production of new plastic and other materials. The use of supercritical water provides an organic solvent, a source of hydrogen to complete the broken chemical chains, a means of rapid heating, avoiding excessive temperatures that would lead to excessive cracking, and a scalable process. This helps to create a circular economy for plastic by diverting those materials that cannot be recycled via traditional means away from landfills and incineration and into recycling, thus reducing unnecessary single-use plastics and reducing carbon emissions. Additional insight taken from the interview with Sudhin Datta The most important classical thermosets that are recyclable are polyurethanes, epoxies, and silicones. Additionally, there are materials which behave like thermosets in the recycling process, such as PVC, Teflon, and PEX, cross-linked polyethylene. The three classical thermosets are recycled for different purposes: • Polyurethanes are recycled because there is a very large volume in the world in the low-density form. There is inherent value in the materials that come out of polyurethane recycling, and the process only takes a couple of hours. It is not being done in North America and Western Europe, as the companies in such regions would much rather export that waste polyurethane foam to lower cost countries in Asia. • Epoxies have inherently no value, but reinforced epoxies are recycled for carbon fibre recovery, which are 10 times more expensive than the epoxy itself. • Silicones are recycled because silicone monomers are very expensive. Other materials face more economic barriers, such as Teflon and PVC: • Thermal recycling turns Teflon and PVC into dark intractable solids while releasing toxic acid gases which damage the equipment. • Teflon recycling is hampered because typically it is present in small quantities by weight and recovering and recycling is economically unjustifiable. • Typical PVC pipes for city water are composed of filled PVCs. So whatever recycling process should first remove the filler, which is a toxic waste that corresponds to around 40 % of the volume. The recycling processes are usually not disclosed by the companies, but they can be understood based on their chemistries: Polyurethanes Chemical structure of polyurethanes Polyurethanes are soaked, and then a glycolysis process is carried out by heating up ethylene glycol (at around 280°C) for about four or five hours and breaking the big molecules down to smaller molecules, which can be distilled and recovered. It is claimed a 95 % efficiency of whatever output material as free monomers. The process is fairly well understood. Epoxies Chemical structure of the epoxide group, a reactive functional group present in all epoxy resins. Chemical structure of silicones (PDMS) Reinforced epoxies are recycled via alcoholysis, or there is typically a catalyzed degradation of the process. The epoxies come off and the catalyst is washed off, so the carbon fibres are recovered. The chemistry is well understood, but there is some work to be done to understand the catalyst. Silicones Silicones are recycled in a similar way to polyurethanes, but the molecules are broken down to polydimethylsiloxane (PDMS). The full report is available from the website. AT www.prescouter.com/inquiry/recycling-of-thermoset-materials/ 34 bioplastics MAGAZINE [03/22] Vol. 17
Not all plastics are recycled equally Floris Buijzen, Senior Product Market Manager Gerrit Gobius du Sart, Corporate Scientist TotalEnergies Corbion, Gorinchem, the Netherlands By Recycling TotalEnergies Corbion has launched the world’s first commercially available chemically recycled bioplastics product. The Luminy ® recycled PLA grades boast the same properties, characteristics, and regulatory approvals as virgin Luminy PLA, and are partially made from postindustrial and post-consumer PLA waste. TotalEnergies Corbion is already receiving and depolymerizing reprocessed PLA waste, which is then purified and polymerized back into commercially available Luminy rPLA. Of the total estimated 8.3 billion tonnes of historic plastic production, only 9 % of the plastic waste (or 0.6 billion tonnes) have been recycled, or about 7 % of all plastics produced [1]. Clearly, the plastics industry is facing a major challenge to realize high recycling rates for all plastics, and bioplastics are no exception to that conclusion. Industrial composting is a well-established end-of-life option for PLA and is preferred for applications like tea bags and coffee capsules, allowing diversion of organic waste from landfill. In addition to its already established end-of-life options, different recycling strategies should be explored and advanced also for polylactic acid or PLA. Over the last years, TotalEnergies Corbion has been working on the different parts of the recycling value chain, from collection, sorting, and cleaning to reprocessing and reuse. Over the last years, numerous closed-loop applications have ensured enough volume to capture the value in recycled yet biogenic carbon on a commercial scale. In such applications, PLA is used in well-controlled environments, is collected after use, cleaned, and finally, chemically recycled. Through this process, biogenic carbon content is kept in the value cycle and reduces the need for biomass in the production process of PLA. Working in close cooperation with the recycling industry, PLA converters and reprocessors, such new PLA feed streams now enable production of increased volumes of commercially available Luminy rPLA at TotalEnergies Corbion’s Thai plant (with an overall PLA production capacity of 75,000 tonnes/a). The company is still working on increasing the availability of recycling volumes and welcomes new partners across the recycling value chain. For the European market, chemical recycling capacity is foreseen in the planned second facility in Grandpuits, France. Currently, Luminy PLA with a recycled content of 20 % is now offered to the market, using a mix of post-industrial and post-consumer PLA feed. Where possible, TotalEnergies Corbion is a strong supporter of mechanical recycling of PLA, but for certain applications, notably those requiring food contact approval, mechanical recycling, whilst arguably most favourable from an LCA standpoint, poses a number of challenges. To overcome the purity requirements for food contact articles, chemical recycling of PLA was developed and upscaled successfully. Contrary to traditional polyolefins like polypropylene, chemical recycling of PLA is much less energy-intensive, yet more selective. As they are not easily depolymerized, pyrolysis of fossil thermoplastics typically requires high energy inputs, high temperatures and produces complex, non-selective mixtures of products [2]. Regarding process selectivity, pyrolysis and cracking are reported to yield at most 19–24 % ethylene and 12–16 % propylene in addition to other chemicals and fuels [3]. PLA on the other hand is selectively broken down by different chemical recycling routes, including depolymerization, esterification, and hydrolysis to lactic acid [4]. These processes are highly selective and give numerous options to valorise PLA waste. Simply looking at the difference in necessary heat while comparing, for example, hydrolysis (possible at relatively mild temperatures) with classical pyrolysis (ranging from 300–900°C), it becomes obvious that these technologies are a far cry from each other in matters of energy consumption. Chemical recycling as such breaks PLA down to its basic building blocks lactide or lactic acid, which can then be transformed into PLA at virgin quality. One could therefore argue that chemical recycling of PLA is a more sustainable process than chemical recycling of some traditional polymers requiring pyrolysis. TotalEnergies Corbion has completed food contact, compostability, and biobased content certifications for its Luminy rPLA offering. A third-party certification of recycled content will be available as of June 2022 as well. An LCA study of Luminy rPLA with 20 % post-industrial and post-consumer waste is being conducted and will be published shortly. The goal remains to significantly increase volumes of mechanical and chemical recycling of PLA and to facilitate the transition to a truly circular economy. [1] KPMG (2019) To ban or not to ban. Available at: https://assets.kpmg/ content/dam/kpmg/uk/pdf/2019/06/to-ban-or-not-to-ban-v6.pdf (Accessed: May 45h, 2022) [2] J.-P. Lange, Managing Plastic Waste: Sorting, Recycling, Disposal, and Product Redesign, ACS Sustainable Chem. Eng. 2021, 9, 15722 [3] Eunomia, Chemical Recycling: State of Play 2020, Petrochemicals Europe Market Overview 2021 [4] R. Narayan, W.-M. Wu, C.S. Criddle, Lactide Production from Thermal Depolymerization of PLA with applications to Production of PLA or other bioproducts, US2013023674 www.totalenergies-corbion.com bioplastics MAGAZINE [03/22] Vol. 17 35
