Upcycling of industrial hemp byproducts into a sustainable molded fiber packaging system

Abstract

This study presents the fabrication and characterization of fully bio-based molded fiber composites using industrial hemp (Cannabis sativa L.) hurds, starch, and cellulose nanofibrils (CNF) for sustainable single-use packaging applications. Hemp hurds, a low-value byproduct of the hemp industry, are usually discarded, which encouraged us to upcycle them into the main ingredient of a molded fiber. A total of three samples were made, tested, and labeled as H12. H20, and H28, each comprising 12 g, 20 g, and 28 g of hemp fiber, respectively. Hemp hurds were incorporated at varying loadings to investigate their influence on the rheological, mechanical, and morphological properties of the molded structures. Rheological analysis revealed that excessive solid content hindered the formation of a continuous starch–CNF matrix and reduced free water, resulting in poorer stress transfer and, consequently, lower storage and loss moduli despite the higher solids content. Consequently, the mechanical performance improved with increasing hurd content up to a threshold. Among all formulations, H20 exhibited the most balanced properties, achieving high compressive (8.70 ± 0.34 MPa), flexural (7.56 ± 0.51 MPa), and impact strength (13.83 ± 1.19 J/m), comparable to or exceeding those of the higher-loading H28. Compressive strength increased by more than 300% compared with conventional molded pulps, while flexural strength decreased. The compression strength in this study was more than three times that of conventional molded pulp. SEM analysis confirmed that H20 possessed a uniform interfacial adhesion between the starch–CNF matrix and hemp fibers, while both excessive (H28) and insufficient (H12) hurd contents resulted in structural irregularities. These findings demonstrate that a controlled composition of natural ingredients can yield molded fibers with strong mechanical integrity and biodegradability, providing a promising route toward sustainable, compostable packaging systems.