Strong, spirulina-based bioplastic breaks down in the compost
Rich in vitamins and minerals, spirulina is a type of blue-green algae commonly used as a dietary supplement that you may have mixed into a drink as a powder or taken in a tablet when you were on a health kick. Now, researchers have used it to create a bioplastic that will degrade in your compost bin in the same amount of time it takes for a banana peel to break down.
We use plastics in many situations because they’re durable and cheap to make. But they’re also everywhere in the environment because they persist for years when we’re done with them. While bioplastics are a step in the right direction, they often have to be processed in commercial composting facilities, which aren’t accessible to everyone.
Now, a team of researchers led by the University of Washington has developed a bioplastic that will degrade in your backyard compost bin. It’s made entirely from powdered spirulina, a biomass of cyanobacteria that can be consumed by humans and animals. Using heat and pressure – the same process used to create conventional plastics – the researchers formed the spirulina powder into a variety of shapes.
“This means that we would not have to redesign manufacturing lines from scratch if we wanted to use our materials at industrial scales,” said Eleftheria Roumeli, corresponding author of the study. “We’ve removed one of the common barriers between the lab and scaling up to meet industrial demand.”
Spirulina was chosen because it can be cultivated on a large scale, and its cells sequester carbon dioxide as they grow, making it carbon-neutral and potentially carbon-negative. And, as a kind of added bonus, it’s fire-resistant.
“Spirulina also has unique fire-resistant properties,” said Hareesh Iyer, lead author of the study. “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.”
Although spirulina has been used before to create bioplastics, the researchers say theirs is stronger and stiffer, a result of altering the temperature, pressure, and time in the extruder during processing.
“We were motivated to create bioplastics that are both bio-derived and biodegradable in our backyards, while also being processable, scalable and recyclable,” Roumeli said. “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.”
Currently, the researchers’ spirulina bioplastics are not ready for industrial usage because, even though they may be strong, they’re brittle, and they don’t respond well to water.
“You wouldn’t want these materials to get rained on,” Iyer said.
The researchers are addressing these issues and exploring designing bioplastics for different situations while continuing to focus on recyclability.
“Biodegradation is not our preferred end-of-life scenario,” said Roumeli. “People don’t often recycle plastics, however, so it’s an added bonus that our bioplastics do degrade quickly in the environment.”
The study was published in the journal Advanced Functional Materials.
Source: University of Washington