Did you know that worldwide, less than 10 percent of plastic ends up being recycled? The rest goes into landfills or pollutes delicate ecosystems where it takes centuries to break down, slowly releasing toxic chemicals and microplastics into the environment.
Despite pushes to reduce our reliance on plastics, their excellent performance means they aren’t going away any time soon. To alleviate the effects of plastic use, materials scientists are concentrating their efforts on developing more eco-friendly alternatives called bioplastics.
“Today’s bioplastics are usually made of biomass fillers in a conventional plastics matrix, which gives them properties similar to petroleum-based plastics,” said Dan Kai, a Senior Scientist at A*STAR’s Institute of Materials Research and Engineering (IMRE). “However, these bioplastics are still not fully biodegradable and generate a substantial amount of microplastics.”
On the other hand, bioplastics made entirely out of plant pulp fibres didn’t stack up to traditional petroleum-based plastics in mechanical strength and waterproofness. In search of next-generation plant-based bioplastics, Kai and his colleagues stumbled upon an unlikely solution—coconuts.
Given that discarded coconut husks are both strong yet fully biodegradable, the team explored the possibility of using coconuts to create a stronger, more resilient plant-based bioplastic.
The researchers described a technique for processing coconut husks using a chemical reaction that strips away lignin, the component that gives plant tissues their stiff structure, to reveal soft and flexible fibres that are easier to work with and allow them to bind together when compressed during bioplastic preparation.
Kai’s team also demonstrated that coconut bioplastics produced using this technique could create more than a simple plastic alternative: it could also be used to create electrochemical biosensors for use in healthcare wearables that monitor biometrics such as blood glucose levels.
“Our bioplastic is much stronger than paper-based biosensors and comparable to commonly used petroleum-based polymers,” said Kai. “The chemical stability and biodegradability of our material make it attractive as single-use sensors for biological fluids such as sweat.”
When compared to other materials, the team’s coconut husk bioplastics were more resistant to bending (flexural strength) and stretching (tensile strength) than some plastic-biomass composites.
© A*STAR Research
However, Kai warns that commercialising coconut bioplastics is likely to be tricky, given that variables such as storage conditions can introduce inconsistencies in the husks and ultimately affect the end product. Moving forward, they plan to improve the physical properties of their bioplastic, as well as investigate its utility in other applications such as packaging and electronics.
“We are also interested in processing other sources of food and agricultural waste such as spent coffee grounds, sugarcane and orange peels, to accelerate sustainable development in Singapore under the Zero Waste Masterplan,” added Kai.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE), Institute of Sustainability for Chemicals, Energy and Environment (ISCE2) and Singapore Institute of Food and Biotechnology Innovation (SIFBI).
