New biodegradable plastics are compostable in your backyard

Date:
July 10, 2023
Source:
University of Washington
Summary:
Researchers have developed new bioplastics that degrade on the
same timescale as a banana peel in a backyard compost bin.


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FULL STORY ==========================================================================
We use plastics in almost every aspect of our lives. These materials
are cheap to make and incredibly stable. The problem comes when we're
done using something plastic -- it can persist in the environment
for years. Over time, plastic will break down into smaller fragments,
called microplastics, that can pose significant environmental and health concerns.

The best-case solution would be to use bio-based plastics that biodegrade instead, but many of those bioplastics are not designed to degrade in
backyard composting conditions. They must be processed in commercial
composting facilities, which are not accessible in all regions of the
country.

A team led by researchers at the University of Washington has developed
new bioplastics that degrade on the same timescale as a banana peel in a backyard compost bin. These bioplastics are made entirely from powdered blue-green cyanobacteria cells, otherwise known as spirulina. The team
used heat and pressure to form the spirulina powder into various shapes,
the same processing technique used to create conventional plastics. The
UW team's bioplastics have mechanical properties that are comparable to single-use, petroleum-derived plastics.

The team published these findings June 20 in Advanced Functional
Materials.

"We were motivated to create bioplastics that are both bio-derived and biodegradable in our backyards, while also being processable, scalable and recyclable," said senior author Eleftheria Roumeli, UW assistant professor
of materials science and engineering. "The bioplastics we have developed,
using only spirulina, not only have a degradation profile similar to
organic waste, but also are on average 10 times stronger and stiffer
than previously reported spirulina bioplastics. These properties open
up new possibilities for the practical application of spirulina-based
plastics in various industries, including disposable food packaging or household plastics, such as bottles or trays." The researchers opted
to use spirulina to make their bioplastics for a few reasons. First of
all, it can be cultivated on large scales because people already use
it for various foods and cosmetics. Also, spirulina cells sequester
carbon dioxide as they grow, making this biomass a carbon-neutral,
or potentially carbon-negative, feedstock for plastics.

"Spirulina also has unique fire-resistant properties," said lead
author Hareesh Iyer, a UW materials science and engineering doctoral
student. "When exposed to fire, it instantly self-extinguishes,
unlike many traditional plastics that either combust or melt. This fire-resistant characteristic makes spirulina- based plastics advantageous
for applications where traditional plastics may not be suitable due to
their flammability. One example could be plastic racks in data centers
because the systems that are used to keep the servers cool can get very
hot." Creating plastic products often involves a process that uses heat
and pressure to shape the plastic into a desired shape. The UW team took
a similar approach with their bioplastics.

"This means that we would not have to redesign manufacturing lines
from scratch if we wanted to use our materials at industrial scales,"
Roumeli said. "We've removed one of the common barriers between the lab
and scaling up to meet industrial demand. For example, many bioplastics
are made from molecules that are extracted from biomass, such as seaweed,
and mixed with performance modifiers before being cast into films. This
process requires the materials to be in the form of a solution prior
to casting, and this is not scalable." Other researchers have used
spirulina to create bioplastics, but the UW researchers' bioplastics
are much stronger and stiffer than previous attempts.

The UW team optimized microstructure and bonding within these bioplastics
by altering their processing conditions -- such as temperature, pressure,
and time in the extruder or hot-press -- and studying the resulting
materials' structural properties, including their strength, stiffness
and toughness.

These bioplastics are not quite ready to be scaled up for industrial
usage. For example, while these materials are strong, they are still
fairly brittle.

Another challenge is that they are sensitive to water.

"You wouldn't want these materials to get rained on," Iyer said.

The team is addressing these issues and continuing to study the
fundamental principles that dictate how these materials behave. The
researchers hope to design for different situations, by creating an
assortment of bioplastics. This would be similar to the variety of
existing petroleum-based plastics.

The newly developed materials are also recyclable.

"Biodegradation is not our preferred end-of-life scenario," Roumeli
said. "Our spirulina bioplastics are recyclable through mechanical
recycling, which is very accessible. People don't often recycle plastics, however, so it's an added bonus that our bioplastics do degrade quickly
in the environment." Co-authors on this paper are UW materials science
and engineering doctoral students Ian Campbell and Mallory Parker;
Paul Grandgeorge, a UW postdoctoral scholar in materials science and engineering; Andrew Jimenez, who completed this work as a UW postdoctoral scholar in materials science and engineering and is now at Intel;
Michael Holden, a UW master's student studying materials science and engineering; Mathangi Venkatesh, a UW undergraduate student studying
chemical engineering; Marissa Nelsen, who completed this work as a UW undergraduate student studying biology; and Bichlien Nguyen, a principal researcher at Microsoft. This research was funded by Microsoft, Meta
and the National Science Foundation.

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Story Source: Materials provided by University_of_Washington. Original
written by Sarah McQuate. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Hareesh Iyer, Paul Grandgeorge, Andrew M. Jimenez, Ian R. Campbell,
Mallory Parker, Michael Holden, Mathangi Venkatesh, Marissa
Nelsen, Bichlien Nguyen, Eleftheria Roumeli. Fabricating Strong and
Stiff Bioplastics from Whole Spirulina Cells. Advanced Functional
Materials, 2023; DOI: 10.1002/adfm.202302067 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230710132950.htm

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