The features of pyrolysis that are most attractive to the plastics industry have made it a bogeyman within the environmental community.

Environmental Protection Agency's (EPA) "Draft National Strategy to Prevent Plastic Pollution," released in April, includes an ambiguous discussion of pyrolysis-based plastics recycling. Read in isolation, it could be taken as a restatement of existing practice for the regulation of chemical production processes. Considered alongside the intensifying campaign against plastics, it might suggest EPA intends to create new regulations that could hobble implementation of pyrolysis-based advanced recycling. Indeed, the discussion refers specifically to the issues most commonly used by nongovernmental organizations (NGOs) to argue against the implementation of pyrolysis-based recycling; but it also reaffirms the legitimate potential of pyrolysis as a recycling technology.

The situation is an ironic consequence of the environmental movement's success in drawing attention to the problem of plastics pollution and the need to reduce plastic waste and increase recycling. The movement has not only gotten governments around the world to take action, it has also spurred the plastics sector to regard the problem as an existential threat and its solution as a strategic imperative. The recent rapid development of pyrolysis-based recycling is a direct result.

Pyrolysis is just one of a wide range of advanced recycling technologies, but it stands out for being a particularly robust, well understood process that can be adapted to diverse waste streams and integrated relatively easily into existing petrochemical infrastructure. The product, pyrolysis oil, is a naphtha-like material that can be cracked in conventional steam crackers to produce the same monomers already used to make plastics.

Pyrolysis has accordingly generated broad enthusiasm and enormous investment from the plastics industry, which regards it as an essential component of any realistic path toward circularity. However, these same characteristics have made pyrolysis a bogeyman within the environmental community, where prominent groups such as Greenpeace and the Natural Resources Defense Council increasingly cast doubt on the viability of plastics recycling while calling for the elimination of plastics altogether.

More questions than answers

The draft pollution strategy, which describes itself as a companion to the National Recycling Strategy issued in November 2021, touches only briefly on the issue of pyrolysis-based recycling. Most of the document is focused on identifying opportunities for voluntary collaboration between EPA and US stakeholders to prevent plastic pollution. In a section titled "Goal and Scope of the Strategy," it states: "The proposed actions under each objective create opportunities to shift from a linear approach in plastic materials management to a circular system that is restorative or regenerative by design, enables resources to maintain their highest value for as long as possible, and aims for the elimination of waste."

It is here that the draft suddenly brings up pyrolysis. "EPA's National Recycling Strategy primarily focused on mechanical recycling of municipal solid waste but welcomed further discussion on technologies often referred to as ‘chemical recycling,' such as pyrolysis," it says. "EPA now understands that some of these technologies produce fuels and/or intermediate materials used in the manufacturing or processing of fuel or fuel substitutes. EPA reaffirms that the Agency does not consider activities that convert non-hazardous solid waste to fuels or fuel substitutes (‘plastics-to-fuel') or for energy production to be ‘recycling' activities."

UP AND RUNNING: ExxonMobil's first 30,000–metric tons per year pyrolysis unit in Baytown, Texas, went online in December.

EPA's position on recycling and fuel is nothing new, and it does not conflict with the industry's plans to use pyrolysis oil as a feedstock for the production of plastics — indeed, it is potentially supportive. Many environmental NGOs argue that pyrolysis should not be considered a recycling technology, claiming that it is used to produce fuel, even when companies use it explicitly to produce monomers for the production of plastic. The draft undercuts this tactic by affirming an explicit distinction between plastics-to-fuel and plastics-to-plastics processing.

The next statement might be more worrisome, as it echoes arguments employed by organizations attempting to block new petrochemical projects in the US: "EPA also aims to ensure that a US circular economy approach for plastic products reduces greenhouse gas emissions and protects overburdened communities from facilities that can increase the generation of hazardous waste and other forms of pollution."

By contrast, the draft's final comments on pyrolysis discuss it specifically as a matter of concern subject to potential regulatory action. "Additionally, EPA is aware of concerns about the potential health and environmental risks posed by impurities that may be present in pyrolysis oils generated from plastic waste," says the draft. "Accordingly, EPA intends to require companies submitting new pyrolysis oil chemicals to the Agency for review under TSCA to conduct testing for impurities that could be present in the new chemical substance prior to approval, and ongoing testing to ensure there is no variability in the plastic waste stream that is used to generate the pyrolysis oil."

How should these comments be read? On the one hand, they only describe the TSCA process, an ordinary function of the EPA. On the other hand, they directly follow what might seem to be a nod to the anti-petrochemical lobby. There is also EPA's silence on whether to regulate pyrolysis-based recycling as manufacturing or waste treatment. EPA issued an advance notice of proposed rulemaking on the matter in 2021, but 18 months after the public comment period ended, the agency has not issued a decision, and doing so is not on the agency's latest regulatory agenda. That the draft's discussion of pyrolysis appears in the manner of an aside further encourages speculation as to its purpose.

Not what might be hoped for

"ACC appreciates the EPA's continued interest in pyrolysis-based recycling," the American Chemistry Council (ACC) said in a statement to Chemical Week. However, the discussion of pyrolysis presented in the draft falls short of what the industry group expects from EPA.

"The draft strategy provides no scientific basis or identifiable source for the alleged health and safety risks. Merely indicating that ‘EPA is aware of concerns,' we believe, fails to provide sufficient clarity for interested stakeholders to provide informed comments on whether EPA's intended approach is justified," said ACC. "In addition, Section 301 of the Save Ours Seas 2.0 Act, which serves as the purported basis for the draft strategy, directs EPA to focus on improving the management and infrastructure of post-use materials in waterways and oceans. ACC questions whether the intended testing requirements for pyrolysis activities fall within that intended Congressional direction."

Susan Bell, research and analysis director/Process Economics Program at S&P Global Commodity Insights, does not believe the comments indicate a change in the EPA's treatment of pyrolysis. "I basically think it is overblown," she said. "Looking at the history of it, there were concerns raised by certain NGOs about advanced recycling and the possibility of toxic components such as dioxins, benzene and related polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals such as lead, cadmium and chromium."

Straightforward solutions to such problems based on operating conditions and supply chain management are well within the capabilities of the petrochemical industry, Bell noted. "First of all, dioxin formation is greatly reduced in the oxygen-free atmosphere of pyrolysis," she said. "The formation of benzene, PAHs, PCBs, and heavy metals [stems from] using poorly sorted plastic waste feedstock such as PVC and waste electrical and electronic equipment."

Bell pointed to the "holistic" approach being taken by Exxon Mobil Corp. and LyondellBasell Industries NV, which have partnered with Cyclyx International to build a $100 million facility in Houston, Texas, for the sorting and processing of plastic waste for both advanced and mechanical recycling. "Instead of just focusing on the pyrolysis process and use of pyrolysis oil in their crackers, they are investing in the plastic [waste] supply chain, including the plastic recycle sorting facilities," she said. "With the investment in plastic sorting technology including newer optical sorting equipment, they should be able to obtain consistent plastic recycle feedstock meeting their specification for advanced recycling, removing unwanted polystyrene, PVC, waste electrical and electronic equipment, and so on."

Bell is sanguine about the prospects for pyrolysis. "Based on the current implementation of large-scale pyrolysis units such as the one ExxonMobil just started up in Baytown, I think a TSCA review of pyrolysis oil will not impede the project," she said.

Asked to clarify the draft's comments, EPA did not respond before Chemical Week's deadline, but a recent letter from EPA assistant administrator Michal Freedhoff to Senator Jeffrey Merkley provides an additional look at the agency's current take on the health and environmental risks associated with the pyrolysis of waste plastic. Dated April 28, the letter responds to concerns expressed by Merkley, chairman of the Appropriations Committee's Subcommittee on Chemical Safety, Waste Management, Environmental Justice, and Regulatory Oversight, "that fuels derived from plastic waste reviewed under the program may present significant toxic chemical exposure to communities living near a refinery."

According to the letter, EPA in 2015 and 2019 approved "plastic-based feedstocks (or precursors)" submitted for TSCA review under premanufacturing notices, although the materials, which were to be blended with petroleum-based fuels, have not been commercialized. Data submitted by the applicant showed "there were no impurities of concern, and in one case the Agency required some additional testing to prove no dioxins were being formed as a result of the pyrolysis process," the letter states.

The letter explains in detail that the associated risk assessments were based on "very conservative" assumptions. It also debunks a news report by ProPublica that claimed communities near the production site would see a dramatic increase in cancer risk. Going forward, however, EPA will apply greater scrutiny, Freedhoff's letter states, explaining that data previously considered sufficient "might not reflect as complete an understanding of the potential range of impurities that the Agency now knows to be potentially present in plastics."

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