Grasstic: Bioplastic sheets made from grass xylan
Plastics accumulate in landfills and leach into the environment, posing an increasing risk to the biosphere. Of all plastic produced in 2020, a massive 36% was used to make packaging - over 100 Megatonnes. It is urgent to find packaging that matches or eclipses the performance of synthetic plastics while also biodegrading. This work describes the development and laboratory scale-up of a xylan-based food packaging. Grasstic bioplastic is made from xylans in Esparto grass and reinforced with microfibrillated cellulose. It is lightweight, forms flexible bags or pouches and uses less material compared to traditional paper-based packaging. The high oxygen barrier properties of xylan as well as its strong interactions with cellulose open up wide applications in food packaging. Moreover, since xylan comprises one-quarter of Esparto grass by weight, Grasstic provides a potential value-added product in the hemicellulose stream of biorefineries. This xylan-cellulose bioplastic showed increased elongation at break and improved toughness compared to the microfibrillated cellulose control sheets. In addition, Grasstic passed water disintegration tests whereas microfibrillated cellulose control sheets did not. With the addition of paper sizing agents, we significantly improved water resistance. Next, Grasstic was evaluated by a trained panel for aesthetic appeal and marketability. The yellow colour was flagged as an area for improvement. Thus, more work was undertaken in the lab to create a semi-transparent and clear film. The demand for single-use packaging is projected to increase to meet consumer demands. This work showcases exciting developments in a biodegradable plastic made from the plant polymer xylan.