Chemical recycling of plastic waste is gaining momentum, according to UK-based consultancy IDTechEx. In the following article, IDTechEx explores the early technologies of chemical recycling and assesses the players and possible commercial implications. For an in-depth analysis of the Chemical Recycling Market, readers may consider the new IDTechEx market report “Chemical Recycling and Dissolution of Plastics 2023-2033”.
When it comes to chemical recycling, the frequency and scale of headlines about investments, planned expansions and actual product launches are accelerating. Is the market now at a stage of mass implementation, regulatory development, and improved tracking and accounting methods? Or, are there still necessary technological developments?
The concept of chemical recycling is to bring end-of-life plastic back to its monomer raw material or further upstream raw material and allow it to re-enter the value chain in virgin grade quality, theoretically unlimited times.
There is still plenty of criticism of the space, especially about its economic and environmental viability, with lobbying and activist groups on both sides of the debate prominent.
As with all things, reality is more nuanced. Are these processes the perfect solution for all our sustainable polymer needs? Do not. Don’t they have any advantages, especially in dealing with a certain percentage of plastic waste that cannot be met by mechanical recycling and would otherwise end up in landfill? So no. Of course, the sustainability discussion is broader than just focusing on chemical recycling, but this article will set this debate aside to focus on current and emerging technological solutions.
Depolymerization. this technique is one of the most exciting fields of chemical recycling; it involves breaking down polymer chains into monomers. This doesn’t work for all polymers, but works very well for some. Monomers will also be of higher value than raw materials, but there are challenges, including process conditions and the requirement for a more uniform scrap feedstock, to name two.
The main commercial front is the depolymerization of polyethylene terephthalate (PET) by methanolysis, hydrolysis, glycolysis or thermal depolymerization of polystyrene (PS). The role of PET in high-volume industries such as bottles, other packaging and textiles makes it an area of focus being explored by young and major companies alike [petrochemical] Industry players, most notably Eastman’s 2022 announcement.
There are several early technological developments, such as the use of ionic liquids, but two processes close to large-scale deployment are worth highlighting:
1. Enzymatic depolymerization. This is using natural or engineered enzymes to degrade plastic waste. [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 activities, as well as Switzerland-based Gr3n, which received funding from Chevron Technology Ventures and Standex International in 2021, with an eye on PET.
Pyrolysis. Using the pyrolysis process on plastic waste is not a new concept. These processes have been researched and commercially explored for decades. The reasons for the positive forecast involve market drivers, leading to commitments from major petrochemical players such as BASF, SABIC and ExxonMobil. Encina announced a $1.1 billion investment in a new plant in 2022 alone; Plastic Energy made progress on its commercialization with announcements surrounding TotalEnergies, Ineos, LyondellBasell, and Qenos. Likewise, Honeywell announced a strategic agreement with TotalEnergies and a joint venture with Avangard. However, as discussed above, it’s not all positive. In 2022, lawmakers and environmental groups sent more than 100 letters to the U.S. Environmental Protection Agency (EPA) about how to regulate, but they have encountered setbacks, such as Brightmark Energy’s cancellation of plans for a $680 million plant. Get ready for more news in 2023.
There are many technical challenges in pre-processing (consideration of degree of sorting, form factor), post-processing (purity, cleavage considerations), and the process itself (yield, molecular weight distribution, light gas macromolecules, durability, etc.). There are limited incremental changes available, but technical improvements are sure to be made at each stage.
other technologies. One of the most dramatic technological developments in a related field is hydrothermal liquefaction. Here, supercritical water and a catalyst are used to break down conjunct polymers into long-chain hydrocarbons. One of the reported strengths is the ability to tolerate lower quality mixed material feedstocks, especially those with a higher proportion of polyvinyl chloride (PVC), a key issue in pyrolysis. As with pyrolysis, this isn’t new, but young companies are gaining a lot of momentum, most notably Licella. Through joint ventures and other collaborations, Australia-based Licella’s core technology has been developed into strategic partnerships and planned projects with companies including Dow Chemical, Mitsubishi Chemical and LG Chem.
Likewise, gasification is not a new process and has been widely used to remove municipal solid waste (MSW), especially in Japan. What is changing is that instead of being used as an on-site energy source, the syngas produced can be purified and converted into long-chain hydrocarbons, methanol or ethanol. With the ability to use MSW, gasification is the final option for any cycle prior to incineration. Players are exploring this. Enerkem is one of the most notable players, with its first commercial plant opening in 2014. As of the end of 2022, Enerkem is also building the 2023 plant, with two more plants planned. It should be noted that, as with pyrolysis, while the product can re-enter the supply chain, it often does not, instead being used as fuel.
Although not discussed in this article, other processes should not be overlooked. This ranges from developing polymers with dynamic bonds to facilitate a circular economy to use in secondary recycling processes for dissolving or purifying plastics. The latter is not chemical recycling, but a promising route to higher-grade materials than other mechanical routes, without going that far down the backup value chain. This is gaining commercial activity through companies such as Trinseo, PureCycle Technologies, APK, Polystyvert and Worn Again; as with other processes, many young technology suppliers can form partnerships with larger players in the plastics value chain.