Hemp waste cellulose unlocks tougher biodegradable plastics

Korean researchers have developed a method to enhance the durability of biodegradable plastics by incorporating hemp hurd cellulose. Led by Dr. Hoyong Kim of the Korea Research Institute of Chemical Technology, the team extracted cellulose from industrial hemp stalks and applied a drying process that preserves the microfibrillar structure, making it suitable as a reinforcing biofiller for biodegradable plastics.

Biodegradable films made from thermoplastic starch and poly(butylene adipate-co-terephthalate) have gained popularity for eco-friendly packaging and agricultural mulch due to their biodegradability. However, these films are prone to tearing and have limited moisture resistance. While cellulose microfibrils from cotton or wood pulp can be used as reinforcing materials, the additional processing steps increase costs.

Industrial hemp, a byproduct of hemp hurd accounting for about 70% of the stalk weight, has limited applications. Using hemp hurd as a feedstock for microfibrillated cellulose could reduce agricultural waste and raw material costs. The researchers overcame the challenge of cellulose microfibril aggregation during drying by developing a two-step physicochemical strategy.

They controlled moisture content and treated the cellulose surface with low-cost alkyl ketene dimer (AKD). The hemp hurd cellulose biofiller, when incorporated at 10 wt% in a TPS/PBAT biodegradable film, increased tensile strength by 26.2% and reduced water vapor and oxygen transmission by approximately 17% and 9%, respectively.

This technique could potentially be applied to other cellulose-rich agricultural residues, such as soybean stalks and rice straw.