Valorization of cannabis stalks into cellulose nanocrystals: A sustainable solution for cannabis waste management

In the cannabis industry, inflorescences are the primary products, while byproducts like stalks are typically discarded due to regulatory constraints on tetrahydrocannabinol (THC) levels. Although stalks usually contain THC below the regulatory thresholds, microbial contamination often leads to the disposal of entire plants as waste. This study investigates the extraction and characterization of cellulose nanocrystals (CNCs) from cannabis stalks through sequential alkali treatment, bleaching, and metal salt oxidation, offering a sustainable solution for cannabis waste valorization. Chemical analysis on raw stalks resulted in 57 % cellulose, 17 % hemicellulose, and 14 % lignin, with total THC content of 0.078 %. A mild NaOH pretreatment (1–3 %, 90°C, 1 h) further reduced total THC to 0.036 % in stalks and from 6.016 % to 0.384 % in mixed biomass (combination of inflorescences, leaves and stalks), suggesting a cost-effective manner to produce reduced-THC cannabis biomass for further utilization meeting regulatory standards. The extracted CNCs exhibited diverse functional groups, a crystallinity of 72 %, and a spindle-shaped morphology with average length of 280 nm, width of 9 nm, and aspect ratio of 34. With a 27 % yield, CNCs from cannabis stalks hold possibilities for applications in bio-composites, adhesives, absorbent and packaging materials. By transforming cannabis waste into high-value nanomaterials, this study supports circular economy principles and offers a sustainable approach to resource optimization in the cannabis industry. • The cannabis industry produces ∼50 % waste, primarily stalks. • Cannabis waste disposal (mainly landfilling) creates cost/environmental burdens. • Stalks contain ∼57 % cellulose, ideal for conversion into high-value bioproducts. • Chemically processed stalks yield ∼27 % cellulose nanocrystals (C-CNCs). • Spindle-shaped C-CNCs exhibit excellent sustainable biomaterial potential.