Chemical recycling of plastic waste is gaining momentum. 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 & accounting methodologies, or are there still necessary technology developments?
In this article, IDTechEx explores the early-stage technologies for chemical recycling and assesses the players and likely commercial impact.
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 the 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 merits whatsoever, particularly in tackling a percentage of plastic waste 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 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 waste feedstock, to give two examples.
The main commercial frontiers are depolymerizing PET by methanolysis, hydrolysis, glycolysis, or the thermal depolymerization of PS. The role of PET in high waste industries of bottles, other packaging, and textiles makes this a key focus area being explored by notable young companies like Loop Industries and major industry players, seen most notably with Eastman’s 2022 announcement.
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:
This is the use of natural or designed 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 AI in the engineered design as demonstrated by UT Austin. This depolymerization approach is typically focused on PET but not limited there, with opportunities with PU, PC, PA, and more, and commercial engagement is increasing. The most prominent company is Carbios, who announced in 2022 that they would build their first plant in partnership with Indorama Ventures. They have a JDA with Novozymes to produce the proprietary recycling enzyme and end-user partnerships, including Pepsi, L’Oréal, On, Patagonia, Salomon, PUMA, Nestle Waters, Suntory Beverage & Food Europe. Carbios are not alone, as many others enter this field. Another emerging company is Samsara Eco in Australia. In Q4 2022, they announced a AUD$54 million Series A funding round to build their first plant; they expect their recycled packaging on supermarket shelves in 2023 in partnership with Woolworths Group.
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. Pyrowave have been operating a reactor for PS for many years and have reported that their recycled product has already gone into many finished goods. Michelin is a key investor and is in the process of installing their first multi-reactor project with the product utilized for their styrene-butadiene rubber. There are others exploring microwaves, including Microwave Chemical in Japan, who work with Mitsubishi Chemical on PMMA and other engagements, and Gr3n, who received 2021 funding from Chevron Technology Ventures and Standex International, looking at PET.
Using a pyrolysis process on plastic waste is not a new concept; they have had decades of research and commercial exploration. The reason for the significant forecasts are the market drivers resulting in commitments from major petrochemical players like BASF, Sabic, and ExxonMobil. In 2022 alone, Encina announced a US$1.1 billion investment in a new plant; Plastic Energy progressed in their commercialization with announcements surrounding TotalEnergies, INEOS, LyondellBasell, and Qenos. Similarly, Honeywell announced a strategic agreement with TotalEnergies and a JV with Avangard.
However, as discussed above, it is not all positive. In 2022 lawmakers and environmental groups delivered over 100 letters to the Environmental Protection Agency EPA concerning how this is regulated, and there have been setbacks with Brightmark Energy scrapping plans for a US$680m plant, for example. Prepare for a lot more news in 2023.
There are numerous technical challenges from the pre-processing (considerations on the degree of sorting, form factors), post-processing (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.
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 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 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 on-site 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 their 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, although 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.
As can be seen, there are lots of scientific developments and engineering challenges in this field that should not be overlooked amongst all the noise in this field.