In some circumstances, according to the European Chemicals Agency, some microplastics are purposely introduced into agricultural chemicals, paints, cosmetics, and detergents. To this end, the European Union (EU) has mandated that nonbiodegradable microplastics be removed by 2025.
Researchers at the Massachusetts Institute of Technology (MIT), and other scientists, have developed a silk-based device that could be cheap and easy to make. The unique concept is described in a study by MIT written by postdoc Muchun Liu, MIT professor Benedetto Marelli, and five others at BASF in Germany and the U.S.
“We cannot solve the whole microplastics problem with one solution that fits them all,” Marelli explained. “Ten percent of a big number is still a big number. … We’ll solve climate change and pollution of the world one percent at a time,” he added.
According to Liu, the silk protein used in the new alternative material is easily available and less expensive. For this usage, non-textile-quality cocoons can be used, and the silk fibers can be dissolved using a scalable water-based technique.
Silk is harmless and degrades naturally in the body, making it suitable for food or medical use. In lab testing, the researchers showed that the silk-based coating material could be utilized in existing spray-based manufacturing machinery to manufacture a water-soluble microencapsulated herbicide product, which was then tested on a corn crop in a greenhouse. Liu believes it worked better than a commercial treatment, causing less plant damage.
Other researchers have proposed degradable encapsulating materials that may work in the lab, but Marelli thinks high-content actives are needed for commercial application.
By altering the polymer chain configurations of silk materials and adding a surfactant, coating features can be introduced.
Liu had to design a mechanism to freeze developing droplets of encapsulated materials to examine their creation. She used a spray-freezing technology to examine encapsulation and better manage it. Some encapsulated “payload” elements, such as insecticides, nutrients, or enzymes, are water-soluble and interact differently with the covering.
“To encapsulate different materials, we have to study how the polymer chains interact and whether they are compatible with different active materials in suspension,” she explained.
The researchers state that the new process can make use of the low-grade silk that is normally wasted because it has no applications.
“This elegant and clever study describes a sustainable and biodegradable silk-based replacement for microplastic encapsulants, which are a pressing environmental challenge,” says Alon Gorodetsky, an associate professor of chemical and biomolecular engineering at the University of California at Irvine, who was not associated with this research.
“The modularity of the described materials and the scalability of the manufacturing processes are key advantages that portend well for translation to real-world applications,” he added.
This process “represents a potentially highly significant advance in active ingredient delivery for a range of industries, particularly agriculture,” says Jason White, director of the Connecticut Agricultural Experiment Station, who also was not associated with this work. “Given the current and future challenges related to food insecurity, agricultural production, and a changing climate, novel strategies such as this are greatly needed.”