The chemical recycling of plastic scrap is gaining momentum, according to United Kingdom-based consultancy IDTechEx. In the article below, IDTechEx explores the early stage technologies for chemical recycling and assesses the players and likely commercial impact. For an in-depth analysis of the chemical recycling market, readers can consider the new IDTechEx market report “Chemical Recycling and Dissolution of Plastics 2023-2033.”
When it comes to chemical recycling, headlines on investments, planned expansions and real-world product launches are all accelerating in frequency and scale. Is this market now at a stage of implementation at scale, regulatory developments and improving tracking and accounting methodologies? Or, are there still necessary technology developments?
The concept of chemical recycling is taking an end-of-life plastic back to either its monomeric feedstock or further upstream to raw materials and allowing it to re-enter the value chain at virgin-grade quality, in theory, an infinite number of times.
There remains a large amount of criticism of this space, particularly concerning its economic and environmental viability, with lobbying and activism groups very prominent on both sides of the debate.
As with everything, the reality is more nuanced. Are these processes the perfect solution to all our sustainable polymer needs? No. Do they have no merit whatsoever, particularly in tackling a percentage of plastic scrap that mechanical recycling cannot satisfy and would otherwise end up in landfill? Also no. Of course, the sustainability conversation is broader than simply focusing on chemical recycling, but this article will leave this debate to one side and focus on the current and emerging technical solutions.
Depolymerization. This technique is one of the most exciting areas of chemical recycling; it involves breaking down polymer chains into their monomers. This is not appropriate for all polymers, but it can be highly effective for some. The monomer will also hold more value than a raw material, but there are challenges, including the process conditions and the requirements of a more homogeneous scrap feedstock, to give two examples.
The main commercial frontiers are depolymerizing polyethylene terephthalate (PET) by methanolysis, hydrolysis, glycolysis or the thermal depolymerization of polystyrene (PS). The role of PET in high-volume industries of bottles, other packaging and textiles makes this a key focus area being explored by both young companies and major [petrochemical] industry players, seen most notably with Eastman’s 2022 announcements.
There are several earlier-stage technology developments, such as the use of ionic liquids, but there are two processes close to larger-scale deployments worth highlighting:
1. Enzymatic depolymerization. This is the use of natural or designed enzymes to degrade plastic scrap. [The field shot into prominence in 2012 with the discovery in Japan of LCC (leaf-branch compost cutinase) and now includes many more, including leveraging artificial intelligence (AI) in the engineered design as demonstrated by the University of Texas-Austin. This depolymerization approach is typically focused on PET but not limited there, with opportunities with polyurethane (PU), polycarbonate (PC), polyamides (PA) and more, and commercial engagement is increasing. The most prominent company is Carbios, which announced in 2022 it would build its first plant in partnership with Thailand-based Indorama Ventures. The company has an agreement with Novozymes to produce the proprietary recycling enzyme and end-user partnerships, including Pepsi, L’Oréal, On, Patagonia, Salomon, Puma, Nestle Waters and Suntory Beverage & Food Europe. Carbios is not alone, as many others enter this field. Another emerging company is Samsara Eco in Australia. In late 2022, it announced a $36.5 million Series A funding round to build its first plant. It expects its recycled packaging on supermarket shelves in 2023 in partnership with Woolworths Group.
2. Microwave-assisted depolymerization. When approaching thermal depolymerization, the ability to achieve efficient heat transfer is essential; this is where microwaves could play a role. As with enzymatic processes, there remains a large amount of academic interest, but the commercial success stories are increasing. One of the key players in the field is Pyrowave. Canada-based Pyrowave has been operating a reactor for PS for many years and has reported that its recycled product has already gone into many finished goods. Tire producer Michelin is a key investor and is in the process of installing its first multi-reactor project with the product utilized for its styrene-butadiene rubber. There are others exploring microwaves, including Microwave Chemical in Japan, which works with Mitsubishi Chemical on Poly(methyl methacrylate) [ PMMA] and other engagements, and Switzerland-based Gr3n, which received 2021 funding from Chevron Technology Ventures and Standex International, looking at PET.
Pyrolysis. Using a pyrolysis process on plastic scrap is not a new concept. The processes have had decades of research and commercial exploration. The reason for positive forecasts involves the market drivers resulting in commitments from major petrochemical players like BASF, Sabic and ExxonMobil. In 2022 alone, Encina announced a $1.1 billion investment in a new plant; Plastic Energy progressed in its commercialization with announcements surrounding TotalEnergies, Ineos, LyondellBasell and Qenos. Similarly, Honeywell announced a strategic agreement with TotalEnergies and a joint venture with Avangard. However, as discussed above, it is not all positive. In 2022 lawmakers and environmental groups delivered more than 100 letters to the United States Environmental Protection Agency (EPA) concerning how this is regulated, and there have been setbacks, with Brightmark Energy scrapping plans for a $680m plant, for example. Prepare for a lot more news in 2023.
There are numerous technical challenges from the preprocessing (considerations on the degree of sorting, form factors), postprocessing (purity, cracker considerations) and the process itself (yield, molecular weight distribution, light gas reuse, durability, etc.). There are limited stepwise changes available, but certainly technology improvements at each stage.
Other technologies. One of the more notable technology developments in a related field is hydrothermal liquefaction. Here, supercritical water and a catalyst are used to break mixed polymers into long-chain hydrocarbons. One of the reported advantages is the ability to tolerate lower-quality mixed material feedstocks, specifically those with a higher proportion of polyvinyl chloride (PVC), which is a key problem in pyrolysis. As with pyrolysis, this is not new, but young companies are gaining significant momentum, the most notable being Licella. Through joint ventures and other engagements, the core technology from Australia-based Licella has progressed to strategic partnerships and planned projects with the likes of Dow, Mitsubishi Chemical and LG Chem.
Similarly, gasification is also not a new process and has been extensively deployed to remove municipal solid waste (MSW), particularly in Japan. What is changing is the idea that syngas generated need not be used for onsite energy, but rather it can be purified and converted into longer-chain hydrocarbons, methanol or ethanol. With the ability to use MSW, gasification acts as the final option for any circularity before incineration. Players are exploring this. Enerkem is one of the more notable players, and its first commercial plant opened in 2014. As of late 2022, Enerkem has a further plant under construction for 2023, and two more are being planned. It should be noted that, as with pyrolysis, though the product can re-enter the supply chain, it often does not and is instead used as a fuel.
Although not discussed in this article, other processes should not be overlooked. This varies from developing polymers with dynamic bonds to facilitate the circular economy to the secondary recycling process for the dissolution or purification of plastics. The latter is not chemical recycling but is a promising route to achieving higher-grade materials than other mechanical routes without needing to go so far back up the value chain. This is gaining commercial activity through the likes of Trinseo, PureCycle Technologies, APK, Polystyvert and Worn Again; as with the other processes, many of the younger technology providers can boast partnerships with major companies across the plastic value chain.
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