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Using laundry detergent enzymes to recycle single-use plastics

7/2/2024

PhD researcher Susana Meza Huaman at work in laboratory Photo: King’s College London
A novel method of chemical recycling developed at King’s College London ‘marks the first step in developing new technologies in waste management for recycling bioplastics that are of equal quality to the virgin product’, according to Susana Meza Huaman (pictured here), PhD researcher on the project

Photo: King’s College London

Scientists at King’s College London have developed an innovative solution for recycling single-use bioplastics commonly used in disposable items such as coffee cups and food containers, which they claim puts the circular economy for plastics within reach.

The novel method of chemical recycling, published in Cell Reports Physical Sciences, uses enzymes typically found in biological laundry detergents to ‘depolymerise’ – or break down – landfill-bound bioplastics. Rapidly converting the items into soluble fragments within just 24 hours, the process achieves full degradation of the bioplastic polylactic acid (PLA). The approach is 84 times faster than the 12-week-long industrial composting process used for recycling bioplastic materials, claim the scientists.

 

This discovery offers a widespread recycling solution for single-use PLA plastics as the team of chemists at King’s found that in a further 24 hours at a temperature of 90°C, the bioplastics break down into their chemical building blocks. Once converted into monomers – single molecules – the materials can be turned into equally high-quality plastic for multiple reuse.

 

The problem with ‘green’ plastics

Current rates of plastic production outstrip the ability to dispose of it sustainably. According to Environmental Action, it is estimated that in 2023 alone more than 68mn tonnes of plastic globally ended up in natural environments due to the imbalance between the huge volumes of plastics produced and current capacity to manage and recycle plastic. A recent OECD report predicted that the amount of plastic waste produced worldwide is on track to almost triple by 2060, with around half ending up in landfill and less than a fifth recycled.

 

While bioplastics – derived from biological sources such as corn starch, cassava or sugarcane – are seen as a more sustainable choice by consumers, current methods of bioplastics production are costly and compete with food-based agriculture for use of land. Meanwhile, mechanical recycling methods are inefficient, generate CO2 and are incapable of producing high-quality reusable materials. These ‘green’ plastics primarily end up in landfill after just one use, causing many retailers to revert back to using fossil-based materials.

 

The speed at which the bioplastics break down using this new method could ‘revolutionise plastic production’, claim the scientists, offering ‘an efficient, scalable and sustainable blueprint for recycling single-use bioplastics’.  

 

The scientists are now extending their research into improving the recycling of other commonly used and mass-produced plastics, such as those used in single-use water bottles, film and sheet plastic packaging, and clothing.