Inside Green Innovation: Progress Report - Fourth Edition highlights:
- Strong global growth continues the recent surge in plastic recycling technology innovation.
- South Korean originating filings have shown the largest increase over the last five years, possibly linked with government interventions in the sector.
- Pyrolysis is still by far the main source of chemical recycling innovation, but there is also growth in other emerging technologies such as metal catalyst depolymerisation and specific types of hydrothermal processes.
- Most chemical recycling innovation relates to PP, PET, and PVC technology, with innovation around PVC and PET carrying the most momentum.
The merits of plastic in today’s society are its wide range of compositions and uses. Polyethylene (PE), polypropylene (PP), polyester, polyacrylic, polystyrene, and polyvinyl chloride (PVC) are all examples of traditional petrochemical-derived plastics, which have specific properties and for a variety of uses. They remain very valuable materials, essential in many areas of modern life, and this will likely continue until greener alternatives can sufficiently replicate their performance. Continued use requires these plastics to become easier to recycle as petrochemical-derived plastic waste is a pollutant, taking decades to biodegrade. Recycling petrochemical-derived plastics is one way to partially mitigate their environmental impact. While in Europe the total amount of plastic being recycled is generally increasing year on year, so is the amount of plastic being produced. A step-change in the amount of plastic being recycled is needed.
Figure 1: Ten-year trend (2013-2022) - plastic waste produced and recycled in the EU (in million tonnes)
(Priority filing = the first time a patent application for a unique invention has been filed (the first filing))
Plastic’s wide range of compositions and uses can also be a weakness when it comes time to recycle. Waste plastics will have a vast array of polymers with various chemical compositions, structures, and properties. Due to this, different polymers often require bespoke recycling processes, which can make recycling challenging. Mechanical recycling (MR) is an established method for recycling plastic waste. Done so by recovering waste thermoplastics through mechanical processes such as grinding, washing, separating, drying, re-granulating, and compounding. The resulting material can then be converted into plastic products. However, there are drawbacks to the MR processes, such as plastics being recycled by this method ultimately ending up in landfill or nature, and not all plastics being able to be recycled through MR. This article endeavours to measure global progress in technologies developed to recycle plastic; to gauge where and which recycling methods are taking hold and the new plastics recycling technologies – or iterations of foundational technology – that are emerging.
Chemical plastic recycling
Chemical plastic recycling (CR) technologies, such as depolymerisation (converting a polymer back into monomers), has great potential. CR technologies provide a way of converting polymeric waste, by changing its chemical structure, back into substances that can be used as raw materials for the manufacturing of further plastics or other products. However, due to the nature of plastics there is unlikely to be a one-size-fits all solution and a wide range of CR technologies are developing.
CR technologies can be broadly separated into three main categories:
- Thermal recycling: processes that use heat to break down polymeric materials into smaller components; the resulting products are purified for use as feedstock for polymer production or for use in other suitable areas, for example, as a fuel. Processes include pyrolysis, gasification, and hydrothermal treatment (HTT).
- Chemical depolymerisation: catalytic or chemical processes that break down the polymers to their chemical building blocks (monomers and oligomers) via a chemical reaction; monomers are recovered from the process and purified for use as a feedstock for polymer production. Processes include solvolysis, hydrolysis, methanolysis, glycolysis and ammonolysis.
- Biodegradation: the breakdown of organic matter by microorganisms, such as bacteria and fungi; for example, polymer-degrading microorganisms may excrete extracellular enzymes which degrade the polymer into smaller molecules e.g., oligomers, dimers and monomer.
Global patent filing trend
Interest in CR technologies is currently very high, with the number of global patent filings increasing dramatically over the last four years (Figure 2). This trend will likely continue, given growing pressure on manufacturers to embrace a sustainable, circular plastic economy and the need to close the gap between the amount of plastic waste produced and recycled.
Figure 2: Thirty-year trend (1993-2022) - global priority filings - chemical recycling
Europe and the US have mainly driven the recent growth in the past five years. However, there has been strong growth in filings from South Korea in the past two years, going from the fourth highest filing territory in 2020, to the second highest filing territory in 2022, overtaking the US. The sharp increase in chemical recycling filings in South Korea in 2021 may have at least partially been driven by the South Korean government’s announcement in 2020 that it aims to reduce plastic waste in the country by 20 percent by 2025. This may provide a good example of how government action can stimulate innovation.
Figure 3: Five-year trend (2018-2022) - global priority filings by jurisdiction - chemical recycling
In our last report (based on data through 2021), Eastman Chemical remained the top filer; however, their percentage share among the top ten filers decreased due to other companies’ beginning to file, or companies increasing their filings at a higher rate (shown in Figure 4).
Figure 4: Ten-year trend (2013-2022) - top filers – chemical recycling
(Patent assignee = the owner of a patent/application, also known as the ‘applicant’ (for a patent application), patentee (for a granted patent), or proprietor.)
Eastman retain a similar share in the patent filings in 2022. However, LG Chemical are now competing for the top spot and have very similar filing numbers to Eastman Chemical, with LG Chemical’s patent filings doubling from 2021 to 2022.
A wide range of CR technologies
In last year’s Inside Green Innovation report, we covered several prominent areas of CR technology, touching on thermal recycling (e.g. pyrolysis) and biodegradation, as well as several other technologies. Pyrolysis (the heating the waste material in the absence of oxygen) continues to remain the most applied method contributing to most of the filings relating to CR, far outstripping filings in related technologies such as gasification and hydrothermal treatment. Patent filings in the area of microbial biodegradation remain relatively low, but have grown steadily since 2015, with the trend continuing in 2022. Many of the filings relate to novel microorganisms having an ability to degrade plastics; or methods of degrading polymers using known microorganisms in combination with novel auxiliary components and/or processing conditions.
This year we have focused on some further emerging technologies:
Metal-catalysed depolymerisation
Metal-catalysed depolymerisation of plastic waste to chemical feedstocks is emerging as a promising way to address global plastic pollution. The number of new patent applications remain relatively low compared to other more popular technologies such as pyrolysis, but it is showing a significant increase in recent years.
Figure 5: Ten-year trend (2013-2022) - global priority filings – metal catalysed depolymerisation
One example of a recycling process using metal catalysis, developed at the University of California, Berkeley, was found to work well with polyethylene – the component of most single-use plastic bags – and polypropylene, the polymer used to make hard plastics. The process also breaks down a mixture of these types of polymers. Previously, methods for recycling these plastics relied on expensive and soluble catalysts. New processes aim to replace these catalysts with more affordable, solid catalysts more commonly used in the chemical industry. Supercritical water Using supercritical water as a solvent is not a new idea – supercritical water is formed when its temperature reaches the critical point of 374.5ºC and pressure reaches 220 bars. Supercritical fluids can act like both a gas and a liquid, often being superior to both. The number of new patent applications that relate to use of super-critical water in recycling plastics has always been relatively small. There was a small wave of applications filed between 2000-2010, but new applications decreased annually. However, patent filings have increased in 2022 to the highest filing number since 2009 and now hydrothermal treatment using super-critical water is a growing area of innovation (Figure 6).
Figure 6: Twenty-year trend (2003-2022) - global priority filings – hydrothermal treatment using super-critical water
One company which has filed patents in this area is Mura Technology Ltd. Mura uses a supercritical water process to convert post-use, flexible and rigid mixed waste streams into fossil-replacement hydrocarbons to make new plastics. The process involves steps such as melt pressurisation, mixing the supercritical water with the melted plastic, and breaking down the plastics into liquid hydrocarbons and gas in a reactor.
Recycling innovation by plastic type
Despite the wide array of different plastics, consumers interact daily with only a handful of them. The most common types of plastics are:
- Polyethylene Terephthalate (PET or PETE) – lightweight, strong, typically transparent and is often used in food packaging and fabrics
- High-Density Polyethylene (HDPE) – strong and resistant to moisture and chemicals, which makes it ideal for cartons, containers, pipes, and other building materials
- Low-Density Polyethylene (LDPE) – softer, clearer and more flexible version of HDPE. It is often used as a liner inside beverage cartons, in corrosion-resistant work surfaces, and other products
- Polyvinyl Chloride (PVC or Vinyl) – hard and rigid plastic is resistant to chemicals and weathering, making it ideal for building and construction, high-tech and medical applications
- Polypropylene (PP) – one of the most durable and heat-resistant types of plastic, making it ideal for applications including food packaging and food storage.
These plastics require different recycling technologies. Some methods of chemical recycling can break down more than one type of plastic. However, due to different types of plastics having a wide range of varying properties, many cannot be recycled together. Therefore, the plastic type must be considered when innovating in chemical recycling.
Figure 7: Ten-year trend (2013-2022) global priority filings – by different plastic types
Figure 7 shows the number of new patent applications over the last ten years by plastic type. While innovation continues to grow across all of the main types of plastic, Figure 7 suggests that PVC and PET innovation is carrying the most momentum. Until 2022, polypropylene (PP) was the plastic most targeted for chemical recycling innovation. However, in 2022, the highest number of priority filings related to polyvinyl chloride (PVC), with polyethylene terephthalate (PET) taking second place above polypropylene.
Implications for innovation and future patent filings
The trend in patent filings increasing since 2019 shows no real signs of slowing down, with an increase in filings again in 2022. Korea is establishing itself as a hub for chemical recycling innovation. It will be interesting to see whether the success of government initiatives in Korea will influence other nations to implement similar schemes and incentives, thereby boosting innovation in this area and resulting in higher global patent filings. Several companies are making promises to use more recycled plastic in their products and packaging. For example, Lego has pledged to make all bricks from recycled plastic by 2032; Nestle promises to not use any plastic in its products that isn’t recyclable by 2025; L’Oreal says all of its packaging will be “refillable, reusable, recyclable or compostable” by 2025 and Proctor & Gamble has said it will “reduce our use of virgin petroleum plastic in our consumer packaging by 50 percent per unit of production (vs. 2017 baseline) by 2030”. It will be interesting to see if these promises are met and whether they cause a further surge of innovation in the next five years. The political and societal pressure, along with government initiatives, reinforces the expectation that CR growth and innovation is set to continue.
Chris Mason Partner
Amelia Barton Patent Attorney