The Evolving Advanced Recycling Supply Chain

The Evolving Advanced Recycling Supply Chain - The Importance of an Industry Feed Specification

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By Richard Riley

By Krista Sutton.

New Energy Risk helps accelerate the commercialization of industrial technologies that are solving global challenges. One of the technology platforms that we see increasingly is pyrolysis technology being deployed in the development of a more circular plastic economy. A key challenge for those developing these projects is securing a bankable feedstock agreement for waste plastic. This challenge is magnified by the fact that the industry has not developed a standardized feedstock specification for pyrolysis of waste plastic.

The Big Picture

As awareness of plastic pollution and the focus on sustainability increase, so does the demand for recycled material in consumer products. This growing market is driven by various factors, such as consumer preferences and willingness to pay more for recycled products, plastic taxes, corporate pledges, recycling mandates, single-use plastic bans, extended producer responsibility programs, disruptions in the global supply chain following China's National Sword policy, subsidized local recycling initiatives, and higher landfill fees.

The current recycling value chain is primarily composed of mechanical recycling processes, which involve sorting, shredding, washing, drying, grinding, melting, granulating, and compounding various plastic streams. These processes produce recycled granules that can replace virgin plastic granules in certain plastic products. However, strict regulations often prevent these recycled products from being used in applications like food-grade packaging.

On the other hand, advanced recycling leverages technologies that decompose plastics at a chemical level into monomers, which can then be fed into petrochemical plants to create new polymers. Although these advanced recycling technologies are being commercialized, the existing supply chain for waste plastics primarily caters to mechanical recyclers, not advanced recyclers. With the scaling up of advanced recycling, it's crucial to differentiate and understand the overlapping and distinct feedstocks required for these processes, as well as to anticipate how the supply chain will transform in the future.

Figure 1 - Generic plastic value chain [10], [11], [12], [13], [14]

How Does Pyrolysis Fit In?

Although pyrolysis is not new and used in other industries, it's emerging as a pioneer technology in the advanced recycling of waste plastics. For a quick refresh on the pyrolysis process, check out Brad Price’s blog post, 'A Primer on Pyrolysis'. The lack of a standardized feedstock specification for plastic pyrolysis presents challenges for startups and businesses within the plastic supply chain.

As pyrolysis technology scales up, two key factors are driving the development of its supply chain and value chain:

1. What pyrolysis product quality can downstream petrochemical plants accept?
2. What streams of plastic are available in large, consistent quantities that can meet those demands?

The main product of plastic pyrolysis is a liquid stream (pyoil) that can be sold either as is or after fractionation to suit various petrochemical industry processes, producing monomers for new plastic products. The operability of pyrolysis plants and downstream petrochemical processes will determine the quality of pyoil and limit permissible contaminants in the feed streams.

Complicating matters, current infrastructure for collecting waste plastic via mechanical recycling at Material Recovery Facilities (MRFs) will influence the availability of various feedstocks.

A Proposed Waste Plastic Feedstock Specification

The Alliance to End Plastic Waste, a global non-profit dedicated to eradicating plastic waste and promoting innovative waste management solutions, conducted a survey among current pyrolysis operators to understand their feedstock streams and contaminants. They compiled these insights into a proposed industry specification, providing a foundation for evolving standards in the sector.

This specification highlights that pyrolysis can handle more contaminants than traditional mechanical recycling, but there are still limitations. One critical specification is the PVC/PDVC content, which must be minimized to mitigate corrosion, despite current sorting technology not being able to entirely eliminate these substances. Another important specification concerns organic contaminants, offering guidance on the acceptable amount of post-consumer plastic for pyrolysis operators and setting a target to reduce organic contaminants in future post-consumer plastic waste streams, thereby enhancing recycling rates.

Figure 2 - From Feedstock Quality Guidelines for Pyrolysis of Waste Plastic published by Alliance to End Plastic Waste August [1]

For more details on each plastic type, see the Appendix below.

Individual pyrolysis operators will have varied specifications based on the economically available feed material in their location, the restrictions of their pyrolysis technology and equipment, as well as differing customer expectations and regulations. Therefore, this generalized target represents industry trends as a whole.

Why Is a Feedstock Specification Important?

Mechanical recycling and pyrolysis plants share overlapping feedstock streams, benefiting from consistent, well-sorted, and clean feed streams. Nonetheless, the purity and contaminant restrictions for mechanical recycling are more stringent. Thus, pyrolysis presents several advantages and opportunities:

1. Ability to process mixed and colored PP and PE streams.
2. Ability to handle multi-material plastics (PP/PE mixed films with small amounts of aluminum, PET, PVC, EVOH, or nylon contaminants).
3. Capability to process feed streams with more organic contaminants, which is a significant barrier in increasing the mechanically recycled post-consumer plastic.
4. Potential to process feeds historically uneconomical for mechanical recycling (e.g., PS and LDPE/HDPE films).
5. Integration into existing petrochemical supply chains, commingling with virgin plastic feedstock materials.
6. Supply to food-grade and medical-grade applications, avoiding the downcycling often seen in mechanical recycling due to contaminants and stress.

However, the drawbacks include energy intensity, the need for highly trained personnel, and the yield limitation (not 100% of recycled plastic feedstock can be recovered as new plastic products). These limitations point to pyrolysis as a complementary solution to mechanical recycling, capable of accepting streams rejected from MRFs but within specified contaminant limits. Pyrolysis can also handle end-of-life plastics that cannot be mechanically recycled and plastic streams historically uncollected due to a lack of economic viability in mechanical recycling.

Establishing a waste plastic pyrolysis plant feed specification is the first step in communicating to all participants in the plastic value chain which resins can be targeted. This specification will evolve with advancements and growth in the circular plastic sector.

A feedstock specification for pyrolysis will impact and be influenced by:

• Expansion and enhancements in waste plastic collection as new recycling infrastructure develops.
• MRFs' adaptation and optimization to meet both advanced and mechanical recycling feed quality requirements and the implementation of advanced sorting technologies (e.g., Infrared spectroscopy, hyperspectral imaging, fluorescence imaging, or using markers and tracers).
• Optimization of pyrolysis plant yields, product quality, and operability.
• Technical innovation in pre- and post-pyrolysis treatment technologies for contaminant mitigation.
• Product recipes, as manufacturers aim for higher percentages of recycled material and adapt to new customer and regulatory requirements for end-of-life product design.
• Market development and transparency, providing standards to compare materials and pricing, which enhance financial market understanding of waste plastic as a resource.
• Collaboration among government, private businesses, research entities, and other parties, leading to more informed policies, quick scaling, increased efficiency, transparency, and sustainability throughout the value chain.

Going forward, the chemically recycled plastic value chain will likely evolve iteratively with market dynamics and technological advances. Progress starts with a shared understanding of recyclable materials and the most economical recycling methods.

Further Reading - How Are Plastics Classified?

To understand how this specification emerged, we need to consider different plastic resins in the context of pyrolysis and mechanical recycling. Plastics are classified by Resin Identification Codes (RICs), used somewhat consistently worldwide and marked on plastic products. It's a common misconception that these symbols mean the plastic product is recyclable; they actually indicate the type of plastic material.

Figure 3 - Resin Identification Numbers [3]

Polyethylene Terephthalate (PET): PET (commonly used in water bottles) is recyclable but must be separated to be mechanically recycled by grinding, cleaning, and remelting back to pellets. Pyrolysis can handle limited PET because it introduces oxygen, yielding gases and char that are not economically viable. Ongoing developments in other chemical recycling processes for PET involve different reactants, catalysts, and conditions, but PET still needs segregation from other plastics and is not suitable for mixed plastic pyrolysis feed.

High Density Polyethylene (HDPE): Rigid HDPE (used in food and cleaning product containers) is recyclable and undergoes collection, sorting, and mechanical recycling. However, a significant portion of HDPE is rejected at MRFs due to organic contamination, color, or additives, leading to landfill disposal. Pyrolysis is more tolerant of contaminants, making rejected HDPE an ideal feedstock.

Polyvinyl Chloride (PVC): PVC (found in pipes, lawn furniture, hoses, window frames) is not usually collected via curbside service but specialty businesses recycle it at specific drop-off locations. The main issue with recycling PVC is its high chlorine content and additives used in manufacturing, forming hydrochloric acid (HCl) in pyrolysis, causing corrosion and acting as a catalyst poison in downstream processes. PVC must be minimized in pyrolysis feed. Although it can be mechanically recycled, the need to separate different formulations limits its use.

Low Density Polyethylene (LDPE): While LDPE (squeeze bottles, film packaging) is not generally recyclable through curbside services, some locations accept it. LDPE plastic bags are often not recycled curbside but can be collected at grocery stores. However, poor system usage results in most bags ending up in landfills. LDPE bags need segregation in mechanical recycling as they jam sorting machinery. LDPE can be used in both mechanical and chemical recycling, subject to overcoming economic barriers.

Polypropylene (PP): PP (pallets, bottle caps, jars, bumpers) is commonly recyclable through curbside services and is a primary feedstock for both mechanical recycling and pyrolysis, accepted in pure or mixed streams with low contaminants.

Polystyrene (PS): PS (packing peanuts, coffee cups) is not readily recycled mechanically and lacks curbside collection programs. Early commercialization of PS pyrolysis is underway despite an underdeveloped supply chain.

Others: Polycarbonate (PC), Acrylics (ABS), and Polyamide (Nylon) are largely contaminants in both mechanical and chemical recycling and not typically collected through curbside programs.

Works Cited

[1] Gendell, Adam, and Vera Lahme. Feedstock Quality Guidelines for Pyrolysis of Plastic Waste. Eunomia, Aug. , p. 43, https://endplasticwaste.org/-/media/Project/AEPW/Alliance/Our-Stories/Feedstock-Quality-Guidelines-for-Pyrolysis-of-Plastic-Waste.pdf?rev=44dcab453b358c80c4dc3&hash=3D9ADCC4DE44ED8E0F2B87A3ACBE

[2] Resin Identification Code (RIC) | Environmental Claims on Packaging: A Guide for Alameda County Businesses. http://guides.stopwaste.org/packaging/avoiding-pitfalls/resin-identification-code.

[3] StackPath. https://www.recyclingtoday.com/article/the-outlook-for-advanced-recycling/. http://guides.stopwaste.org/packaging/avoiding-pitfalls/resin-identification-code

[4] Chemical and Mechanical Recycling Can Coexist. Will They? 16 Sept., https://www.ptonline.com/blog/post/chemical-and-mechanical-recycling-can-coexist-will-they-

[5] StackPath. https://www.recyclingtoday.com/news/greenback-chemical-mechanical-recycling-coexist-europe-uk/. Accessed 28 Mar.

[6] Circular Plastics | Economist Impact. https://impact.economist.com/sustainability/circular-economies/inside-the-circle-circular-plastics. Accessed 28 Mar.

[7] What Can Go in Your Curbside Recycling Bin? | LoadUp. https://goloadup.com/what-can-go-curbside-recycling-bin/. Accessed 28 Mar.

[8] Brooks, Amy L., et al. "The Chinese Import Ban and Its Impact on Global Plastic Waste Trade." Science Advances, vol. 4, no. 6, June , p. eaat. DOI.org (Crossref), https://doi.org/10./sciadv.aat.

[9] Mangold, H. and von Vacano, B. (2021), The Frontier of Plastics Recycling: Rethinking Waste as a Resource for High-Value Applications. Macromol. Chem. Phys., 223: . https://doi.org/10./macp.

[10] Petrochemical icons created by Eucalyp - Flaticon

[11] Waste icons created by noomtah - Flaticon

[12] Oil refinery icons created by maswan - Flaticon

[13] Plastic icons created by photo3idea_studio - Flaticon

[14] Landfill icons created by Umeicon - Flaticon

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