ENZYCLIC: Unlocking the potential of enzymatic recycling of plastics

The ENZYCLIC project combines biochemistry, chemistry, and social sciences to accelerate the development of new technologies for the recycling of plastics.

Author: Ravindra Reddy Chowreddy, Norner. ravindra.chowreddy@norner.no

At the present rate of growth, plastic production is estimated to double within the next 20 years. A projected increase in future plastic use will result in a concomitant increase in post-consumer plastic waste and environmental concerns. Given these challenges, plastic recycling has become increasingly important to mitigate the environmental impact of plastic waste.

The most common method of plastic recycling is mechanical recycling, in which the plastic waste is physically transformed into a reusable material or product. Mechanically recycled plastics often represents a lower performance and are often blended with virgin plastic material to achieve acceptable performance. Chemical recycling is an alternative method that compliments mechanical recycling when the plastic wastes are difficult to recycle by mechanical means. In this case, the polymer is broken down into building blocks of hydrocarbons.

Chemical recycling of plastics is challenged by low recycling rates and undesired byproducts. To improve the plastic recycling rates, innovative, sustainable, and eco-friendly approaches are being explored in this project. One such approach is the biochemical recycling of plastics into monomers in the presence of microorganisms or enzymes. Such enzymatic recycling methods are being utilised to depolymerise polyethylene terephthalate (PET) into its constituent monomers. In the enzymatic recycling process, commercial enzymes like cutinases, lipases, and esterases are utilised to selectively hydrolyse the ester bonds.

The Enzyclic project, funded by the Norwegian Research Council, is a collaborative interdisciplinary project to develop enzyme-based technological solutions for the recycling of existing plastics and novel biodegradable plastics. The project is led by the Norwegian University of Life Sciences (NMBU). Besides Norner Research, Bellona, Aclima, and the Norwegian Packaging Association participate. The Faculty of Chemistry, Biotechnology, and Food Science at NMBU is a hub for interdisciplinary research, and it covers a wide range of scientific fields, from basic natural sciences to their applications in food, biotechnology, and environmental science. The Bellona Foundation is an independent non-profit organisation that is striving to identify and implement sustainable environmental solutions. Aclima is a textile producer with a target to find sustainable solutions to recycle synthetic fibres. The Norwegian Packaging Association is involved through the Circular Packaging Cluster with the goal of sharing knowledge about challenges and regulations of the packaging sector and having clear objectives of encouraging sustainable packaging. As a participant in the Enzyclic project, Norner has several major tasks:

• Developing novel aliphatic polyesters with superior properties that are amenable to enzymatic degradation.

• Exploring various technologies to modify conventional polymers to make them susceptible to enzymatic degradation.

• Supporting the project with various analytical methods to determine the plastics' physical, chemical, and thermal properties and the degradation products.

The Enzyclic project is an ambitious project where NMBU will identify enzymes for plastic degradation by adopting state-of-the-art (meta) genomics and proteomics techniques to explore the enzymatic machinery of plastic-degrading microorganisms and insects. NMBU will also screen and re-design powerful oxidative enzymes that naturally target recalcitrant and crystalline surfaces of biopolymers to target conventional plastics.

Norner will produce novel polyesters in our lab pilots and modify conventional polyolefins to make them more susceptible to enzymatic degradation. In addition, Norner will develop methods for extraction, purification, and reuse of plastic degradation products. The ultimate target of the project is to depolymerise plastics into monomers through biotechnological routes and to regenerate new polymers from the monomers obtained from the degradation process.

Highlights

• Norner Research has produced 13C isotope enriched polyolefins in research scale for traceability investigations in enzymatic degradation studies.

• Performed partial degradation of commercial polyolefins through thermal and UV degradation for enzymatic degradation experiments.

• Currently, a range of aliphatic polyesters are being produced for enzymatic recycling evaluations.