Waste from hemp essential oil production: How distillation methods shape the byproducts value

The valorization and reuse of waste products is a hot topic within the circular economy framework of industrial hemp (Cannabis sativa L.). The distillation of hemp biomass to produce the essential oil (EO) generates a notable amount of waste (spent biomass and residual water) worthy of reuse for the recovery of several bioactives, i.e., cannabinoids and polyphenols. Given this, it has been hypothesized that both the distillation method and its duration may influence the composition and yield of bioactive compounds from these byproducts. Thus, the aim of this study was to evaluate the effect of different techniques for the EO recovery [steam-distillation (SD), hydrodistillation (HD), and microwave-assisted hydrodistillation (MAH)] from the inflorescences of the monoecious cv. Felina 32 combined with different distillation times (60, 120, 240, 360, and 480 min) on: (i) cannabinoids content in spent biomass extracted through supercritical fluid extraction (SFE), (ii) phenolic compounds in lyophilized residual water. All distillation techniques and durations were effective for the decarboxylation of cannabinoid acids in the residual biomass with the consequent formation of their neutral forms (mainly CBD) in high amounts. The residual water was found to be enriched in luteolin and apigenin derivatives. Hence, this work demonstrated that different distillation techniques and durations for hemp EO production can yield valuable residual byproducts (spent biomass and residual water) suitable for further industrial applications.