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Scientists invent method to transform near-unbreakable plastic into biodegradable polyester

Polyethylene is the most important and widely used plastic in the world and it is used in a wide range of consumer plastics. It is also incredibly difficult to break down in nature. A new research project aims to enable the recycling and upcycling of polyethylene by converting it into biodegradable polyester through a three stage chemical and biological process.

Associate Professor Bekir Engin Eser (right), Professor Zheng Guo (centre) and Associate Professor Patrick Biller (right) together form the core of the Danish research team spearheading the international project ACTPAC, which aims to combat environmentally problematic plastic. Photo: Anders Trærup.

Plastic is hard to break down in nature. Polyethylene (PE) is particularly tough because its strong molecular structure is highly resistant to oxygen, sunlight and biodegradation. PE is also the most important and widely used plastic, accounting for approximately 34 per cent of all plastic produced. Today, only 12 per cent of PE is recycled and only one per cent is converted into high-value products.

But PE can actually be broken down, transformed and recycled. Though it requires a combination of chemical and biological technologies including highly specific catalysts, recombinant microbial systems and the right enzymes.

An international team of researchers, led by Aarhus University, has now been granted € 4.8 million (DKK 35.5 million) from the EU Framework Programme for Research and Innovation, Horizon Europe, to develop an industrially viable method to convert PE into biodegradable polyester and other high-value products. The project is called ACTPAC, short for “A complete transformation Path for C-C backboned plastic wastes to high-value chemicals and materials”.

"It’s usually very difficult to degrade PE due to the strong carbon bonds that form the molecular backbone of this type of plastic. But in collaboration with a wide range of other researchers, we have identified enzymes, microorganisms and chemical processes that can do this. In the ACTPAC project, we will demonstrate a fully industrially viable method to convert PE first into alkanes and then into biodegradable polyester and high-value products for the chemical industry," says Professor Zheng Guo from Aarhus University's Department of Biological and Chemical Engineering, who is leading the project.

A full 80 per cent of all plastics produced today contain these strong carbon bonds, which is why incineration and landfill are the most common methods of plastic disposal. However, the production of plastic has only increased in recent decades, making plastic waste a huge problem – especially when only such a small fraction is converted into high-value products. 

In the ACTPAC project, 11 partners across eight different countries will develop a system with a three-part technology that can (1) convert PE into alkanes, then (2) into high-value chemicals (monomers) through bio-based processes and finally (3) convert these into fully biodegradable polymers via enzyme-catalytic processes.

The ACTPAC project will then upscale the entire system for demonstration at pilot scale.

"This project is a major milestone in bio-based and catalytic degradation of plastics and a big step towards a zero-waste solution to what is currently a huge pollution problem, namely managing plastic waste," says Zheng Guo, and he continues:

"Today, there’s a huge need to develop new ways for innovative upcycling of plastic waste. With ACTPAC, we’re establishing the most profitable upcycling scenario for a pollution-free solution for PE and we’re moving towards a paradigm shift in the plastics economy."

The Horizon Europe-funded project started in January 2024. The project is being led by Professor Zheng Guo from Aarhus University, but it involves researchers from a wide range of disciplines. The project has 11 partners besides Aarhus University: Utrecht University, the University of Münster, Centre National de la Recherche Scientifique (CNRS), the University of Groningen, AIMPLAS, Krechnologies (Biolynx), Innovaplast, Minds & Sparks, B4PLASTICS and CTCR.


Professor Zheng Guo
Aarhus University, Department of Biological and Chemical Engineering
Mail: guo@bce.au.dk
Tel.: +4525580652

Lektor Bekir Engin Eser
Aarhus University, Department of Biological and Chemical Engineering
Mail: bekireser@bce.au.dk
Tel.: +4552824813