Combining Starch With PLA Improves Its Industrial Compostability

August 08th 2023

Combining starch with PLA improves its industrial compostability, researchers claim.

Published in ACS Sustainable Chemistry & Engineering and supported by the US Department of Agriculture and MSU AgBioResearch, the team’s research suggests that PLA can sit in industrial composting conditions for around 20 days before microbial decomposition begins. In response, thermoplastic starch derived from carbohydrates has been precisely implemented into PLA, which apparently provides a substance for the microbes to break down while the PLA degrades.

A collaboration between postdoctoral researcher Anibal Bher and doctoral students Pooja Mayekar and Wanwarang Limsukon combined their knowledge to draw upon Bher’s existing research into the strength, clarity, and other benefits of different PLA-thermoplastic starch blends, as well as observe the difference between breakdown processes under different conditions.
If managed correctly, PLA’s waste byproducts are water, carbon dioxide, and lactic acid – all natural substances that would not cause negative environmental impacts. In addition, PLA itself is already derived from plant sugars instead of petroleum; and, with less than 10% of plastic waste thought to be recycled in the US, composting them in industrial conditions would save both consumers and recyclers the time, water, and energy needed to clean plastic waste for recycling.

Inside this conditioned chamber in Rafael Auras’ lab at Michigan State University, researchers can regulate composting conditions, including temperature, humidity and airflow, while measuring the carbon dioxide produced by microbes as they digest materials in the bioreactors. Credit: Matt Davenport/MSU

Rafael Auras, MSU professor, the Amcor Endowed Chair in Packaging Sustainability, and leader of the project, explained: “In the U.S. and globally, there is a large issue with waste and
especially plastic waste.

“By developing biodegradable and compostable products, we can divert some of that waste. We can reduce the amount that goes into a landfill.”

However, the researchers highlight that social and behavioural factors will need to change to implement their solution at a larger scale. This apparently includes the scepticism of industrial composters surrounding bioplastics and consumers’ misguided belief that biodegradable and compostable materials will break down effectively in every environment, with the latter
contributing towards litter.

Therefore, the team now seeks to raise awareness around the necessary changes in behaviour to further the pursuit of circularity for plastic materials like PLA. “There’s not going to be one solution to the entire problem of plastic waste management,” said Mayekar. “What we’ve developed is one approach from the packaging side.

“It’s really easy to just blame plastic for its problems, but I think we need to change the conversation about how we manage it.” Auras continued: “If people think we develop something biodegradable so it can be littered, that will make the problem worse. The technology we develop is meant to be introduced into active waste-management scenarios.”

“We need to be conscious of how we manage waste, especially plastics,” added Bher. “Even at home, you’ll need to think about how you’re managing that small composting process.”
Another recent breakthrough saw researchers at the University of Washington claim to develop new bioplastics that apparently break down at the same rate as a banana peel in a home compost bin. This is hoped to prevent plastics from creating microplastic pollution if they escape recycling streams.

Meanwhile, European Bioplastics has predicted that the global capacity of bioplastic production will increase by 4.7 million tonnes between the end of 2022 and 2027.


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