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Biodegradable microplastics: US researchers develop novel algae-based compostable polymers

#Biodegradable microplastics: US researchers develop novel algae-based compostable polymers

26 Mar 2024 — New research from the University of California San Diego, US, and materials-science specialist Algenesis shows that the company’s novel plant-based polymers range biodegrades — even at the microplastic level — in under seven months.

“We’re just starting to understand the implications of microplastics. We’ve only scratched the surface of knowing the environmental and health impacts,” says professor of Chemistry and Biochemistry Michael Burkart, one of the paper’s authors and Algenesis co-founder.

“We’re trying to find replacements for materials that already exist, and make sure these replacements will biodegrade at the end of their useful life.”

Robert Pomeroy, paper author, and professor of Chemistry and Biochemistry and Algenesis co-founder, adds: “When we first created these algae-based polymers six years ago, our intention was that they be completely biodegradable.”

“We had plenty of data to suggest that our material was disappearing in the compost, but this is the first time we’ve measured it at the microparticle level.”

The paper was published in Nature Scientific Reports.

Degradable microparticles
To test its biodegradability, the team ground their product into fine microparticles, and used three different measurement tools to confirm that, when placed in a compost, the material was digested by microbes.

The first tool used was a respirometer. When the microbes break down compost material, they release CO2, which the respirometer measures. The results were compared to the breakdown of cellulose, which is considered the industry standard of 100% biodegradability. The plant-based polymer almost fully matched the cellulose.

Next, the team used water flotation. Since plastics are not water soluble and float, they can be scooped off the surface of water easily. At intervals of 90 and 200 days, almost 100% of the petroleum-based microplastics were recovered, meaning none of it had biodegraded.

But after 90 days, only 32% of the algae-based microplastics were recovered, showing that more than two thirds of it had biodegraded. After 200 days, only 3% was recovered, indicating that 97% of it had disappeared, stress the researchers.Particle count under microscope.Particle counts of petroleum-based (EVA) and plant-based (TPU-FC1) microplastics show that, over time, EVAS exhibit virtually no biodegradation, while the TPUS have mostly disappeared by day 200 (Image credit: Algenesis).

Plant-based polymers
The last measurement involved chemical analysis via gas chromatography spectrometry, which detected the presence of the monomers used to make the plastic, indicating that the polymer was broken to its starting plant materials. Scanning electron microscopy further showed how microorganisms colonize the biodegradable microplastics during composting.

“This material is the first plastic demonstrated to not create microplastics as we use it,” asserts Stephen Mayfield, a paper co-author, professor at School of Biological Sciences and co-founder of Algenesis.

“This is more than just a sustainable solution for the end-of-product life cycle and our crowded landfills. This is actually plastic that is not going to make us sick.”

Creating an eco-friendly alternative to petroleum-based plastics is only one part of the long road to viability, say the researchers. “The ongoing challenge is to be able to use the new material on pre-existing manufacturing equipment that was originally built for traditional plastic, and here Algenesis is making progress.”

The scientists have partnered with several companies to make products that use the plant-based polymers developed at UC San Diego, including Trelleborg for use in coated fabrics and RhinoShield for use in the production of cell phone cases.

“When we started this work, we were told it was impossible,” states Burkart. “Now we see a different reality. There’s a lot of work to be done, but we want to give people hope. It is possible.”

Edited by Natalie Schwertheim

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