Pyrolysis under fire: Environmental and health concerns cast doubt on “miracle” technology

27 Oct 2023 --- A new report published by environmental network Zero Waste Europe (ZWE) challenges the effectiveness of pyrolysis, dubbed by some as a “miracle” technology. Pyrolysis involves heating plastic waste without oxygen, and has been promoted for its ability to recycle plastic waste into a “virgin-like” state.

However, the report, titled “Leaky loop recycling: a technical correction on the quality of pyrolysis oil made from plastic waste,” exposes the technology’s limitations and challenges the industry’s claims.

The report highlights the issues surrounding pyrolysis oil: One of the primary concerns is the incompatibility of pyrolysis technology with various plastic types, resulting in limited practical application.

Additionally, the report underscores the low yield of pyrolysis oil and the need for contamination control, which often necessitates dilution with petroleum-based mixtures. In some cases, a ratio of over 40:1 is required to make pyrolysis oil usable.

These findings raise questions about the environmental viability of pyrolysis technology, especially in the context of the EU’s Green Deal. The report urges decision-makers not to compromise safety standards and overlook the toxic compounds and purification requirements associated with pyrolysis oil in the pursuit of a circular economy.

“In the context of packaging waste recycling, the EU Packaging and Packaging Waste Regulation is going in the right direction by directly acting at the production level with recyclability requirements to have on the market only recyclable packaging on the market by 2030,” Lauriane Veillard, chemical recycling and plastic-to-fuels policy officer at Zero Waste Europe, tells Packaging Insights.

“More concretely, this means that packaging is being developed considering the capacities of technologies to handle the different materials and moving toward monomaterial products, for example, and acting on the inherent difficulties related to inks.”

Even under the best-case scenario, only 2% of the plastic waste subjected to pyrolysis is recovered in the “recycled” product.“Highly disputable” claim
Veillard explains that the substantial energy demands of pyrolysis technology have multifaceted repercussions. Firstly, its energy requirements are notably high, and these needs are intricately linked to the diverse energy grids of EU member states, significantly influencing overall environmental performance.

Moreover, should the availability and sustainability of the energy source become limited or environmentally unsound, the technology’s long-term viability is directly imperiled. 

Furthermore, Veillard emphasizes the pyrolysis process exhibits a noteworthy issue — a substantial leakage of plastic materials, with approximately 53% of the carbon content being either lost during the process or converted into fuels. “This must be equally considered as a leakage of materials from a circular management perspective,” she says.

Another critical issue brought forth by the report revolves around the release of dioxins — highly toxic compounds borne as unwelcome by-products during specific manufacturing procedures. 

“Particularly, in the plastic waste pyrolysis process, where plastic waste is heated in the absence of oxygen, conditions are created that encourage the formation of dioxin precursors. The latter is a significant issue both environmentally and in terms of human health, as these substances are recognized as carcinogenic,” says Veillard.

“All plastics, though notably the polyolefins identified as ideal pyrolysis feedstocks, do not simply revert to the precursor material from which they were formed. Therefore, the claim to have a ‘virgin-like quality’ for recycled content from pyrolysis is highly disputable.”

Challenges and limitations of pyrolysis
One of the notable challenges identified in the ZWE report is the low oil yield of pyrolysis technology. Even under the best-case scenario, only 2% of the plastic waste subjected to pyrolysis is recovered in the “recycled” product. ZWE report urges decision-makers not to compromise safety standards and overlook the toxic compounds and purification requirements associated with pyrolysis oil.

The report’s author, Dr. Andrew Rollinson, explains, “physical laws dictate that pyrolysis is designed to synthesize new molecules, not merely decompose plastic polymers. Encouragement alone will not be enough to make pyrolysis solve the problem of plastic waste created by linear thinking in plastic production.”

The report’s findings cast doubt on the effectiveness of pyrolysis technology as a viable solution for plastic waste management, prompting a critical reevaluation of the industry’s claims and the role of pyrolysis in the transition to a circular economy.

“One of the main outputs of the report is that pyrolysis oil must undergo energy-intensive purification or be highly diluted with virgin petroleum naphtha to be used in recycled plastic production. This is required because of the contaminants inherently present in the plastic-derived pyrolysis oil, which is a sink for the many metals used as plastic additives,” Veillard tells us.

“Contaminants like iron, arsenic, or aluminum are way above the steam cracker limit value. Despite washing and pre-treatment steps, these metals are still bonded to the plastic and cannot be removed to the desired limit value, therefore, it is not a ‘drop-in’ in the system. In addition, the pyrolysis process, by its nature, produces new, unwanted and toxic hydrocarbons.” 

By Radhika Sikaria