Belgian researchers discover new chemical recycling technique using pyrolysis oil
07 Oct 2022 --- Researchers from Ghent University, Belgium, have found that using pyrolysis as an advanced plastic waste recycling system could close the gap between petrochemical plastic production and end-of-life waste management such as downcycling, incineration and landfilling.
Pyrolysis is chemical decomposition by using thermal energy at high heat. Performing pyrolysis on plastic waste creates an oil hydrocarbon, also known as bio-oil, that contains many different chemical compounds to be used for further chemical processing.
Until now, pyrolysis has not been used as a recycling system, making an alternative solution to the increasing plastic and packaging waste crisis. However, some experts negate thermal decomposition to make pyrolysis oils as a form of recycling.
Pyrolysis oil
Pyrolysis decomposes materials into their original chemical components. These chemicals can then be re-built to create new packaging in order to form a circular system instead of other common methods that negatively impact the environment.
The chemical compounds in the pyrolysis oil depend on what type of waste was thermally decomposed. For example, polyolefins (PE and PP) solely contain carbon and hydrogen, making them similar in hydrocarbon feedstocks of fossil origin. This could make pyrolysis oil a potential material to substitute crude oils within the petrochemical processes.
Ghent University researchers discover how to use pyrolysis for chemical recycling. Pyrolysis breaking packaging down to its base chemicals creates virgin-quality polymers which work as building blocks to creating other packaging and keeps carbon, a valuable compound in creating packaging materials, in the production loop.
“High-quality petrochemical feedstocks can be produced from plastic waste, which, combined with electrification, could lead to a CO2 emission reduction of 90% compared to incineration as the current mostly used disposal method,” the study cites.
Contamination limiting recycling
High contamination of plastic waste is a main factor in why chemical recycling produces fewer materials than originally went into the process. The researchers state the greatest obstacle in chemical recycling is the complex composition of real plastic waste and its contamination with numerous additives and residues.
Dehalogenation occurs during pyrolysis, degrading hazardous halogenated molecules or to transform them into other less harmful compounds is the most effective waste pre-treatment. Decontamination takes place during and after pyrolysis, the intense heat getting rid of any harmful chemicals, making the oil created suitable for food packaging.
“The decontamination techniques range from waste pre-treatment to reduce the halogen and additive contents, via in-situ techniques applied during pyrolysis to post-treatment techniques to purify the obtained pyrolysis oils using hydrotreatment, filtration or adsorption,” states the report.
The scientists state the lower quality of pyrolysis products compared to fossil feedstocks needs to be drastically improved by universally applicable upgrading and decontamination techniques.
The study recommends that combinations of different treatment steps and recycling techniques will have the highest economic potential.
a Rabobank specialist told PackagingInsights that they expect the number of chemical recycling facilities will more than double before 2025, reaching over 200.
Issues with scaling
However, the EU does not consider chemical processes that create pyrolysis oils a form of recycling.
Contamination of waste streams is a large concern when it comes to the technical applicability of pyrolysis oils. If largely scaled the current plant units are designed for fossil feedstocks, it is still uncertain if pyrolysis oils are feasible feedstocks in the long run.
By Sabine Waldeck
