Researchers from the University of Washington have developed new bioplastics that can degrade just as a banana peel in a backyard compost bin.
Many industries have turned to bio-based plastics in order to avoid pollution and microplastics. However, a majority of these are not designed to degrade in backyard composting conditions and must be processed in commercial composting facilities, which are not accessible everywhere.
The researchers produced the new bioplastics completely from powdered blue-green cyanobacteria cells, also known as spirulina. They used the same techniques used for conventional plastics of heat and pressure to mold the spirulina powder into various shapes.
“We were motivated to create bioplastics that are both bio-derived and biodegradable in our backyards, while also being processable, scalable, and recyclable,” says senior author Eleftheria Roumeli, assistant professor of materials science and engineering at the University of Washington. “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.”
One of the reasons the authors decided to use spirulina is its ease to be cultivated on large scales. As a bonus, 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,” says lead author Hareesh Iyer, a 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.”
The team optimized microstructure and bonding within these bioplastics by altering their processing conditions and studying the resulting materials’ structural properties, including their strength, stiffness, and toughness. Nonetheless, the new bioplastics are brittle and sensitive to water.
The researchers are working on these issues and hope to design for different situations by creating an assortment of bioplastics.
