From Waste to Resource: Mineral and Biochemical Characterization of Hemp By-Products in the Fiber and Seed Supply Chain

Industrial hemp (Cannabis sativa L.) is a versatile and sustainable multipurpose plant for agroecology services and a zero-waste circular economy. While the focus has traditionally been on primary products like fiber and seeds, nowadays there is an increasing awareness of the potential value of the by-products generated during hemp cultivation and processing. This article explores various methods of valorizing industrial hemp wastes, focusing on their mineral and biochemical composition, highlighting the benefits of utilizing what was once considered a mere by-product. The apical and the basal leaves of 12 industrial hemp varieties, six monoecious, and six dioecious, representing the main by-product of fiber supply chain, were assessed for their mineral (N, K, Na, Ca; Mg, Cu, Mn, Fe, and Zn), chlorophyll, carotenoids, and total soluble phenols contents, as well as for their antioxidant activity. The same parameters were also evaluated in the inflorescences; the main waste was derived from both hemp fiber and seed harvesting, which were collected at three stages of flower development for four selected genotypes, together with the yield and chemical composition of their essential oils. Differences in the evaluated parameters among genotypes and tissues were highlighted, showing the potential for diversifying the utilization of industrial hemp wastes. The possible uses of these residual biomasses are discussed based on their composition.