From residue to resource: The multifaceted environmental and bioeconomy potential of industrial hemp (Cannabis sativa L.)

In the emerging context of circular bioeconomy, industrial hemp (Cannabis Sativa L.) biomass is a valuable resource for the sustainable implementation of second-generation biorefineries. Potentially, all the main hemp components can find application within different biorefinery approaches, adding value to the conventional production of hemp fibres and seeds. Hurds, leaves and inflorescences, constituting most of the hemp plant biomass, and often considered as low-value residues, can indeed play a key role in the sustainable production of both bioenergy and high-value bioproducts. The present article reviews the advances and outlines the potential future perspectives of hemp-based biorefineries. After critically overviewing some of the most established applications of hemp, spanning from soil bioremediation to bioenergy and biofuel production, particular attention is given to novel valorisation schemes to synthetize highly demanded bioproducts such as microbial protein and biopolymers. Our preliminary calculations show that hemp biomass can sustain high biodiesel yield (1.6 g/g VS (volatile solids)) and related revenues (510–868 €/ha•year), while bioethanol production can yield 0.10–0.33 mL/g VS, profiting between 75–325 €/ha•year. Moreover, hemp suits biomethane production by yielding and profiting 98–426 mL/g VS and 60–380 €/ha•year, respectively. High yields of polyhydroxybutyrate (0.13 g/g VS) can be obtained, albeit high production costs might restrain their marketability. Finally, the biomethane-to-microbial protein pathway can yield and profit 0.03–0.15 g/g VS and 141–893 €/ha•year, respectively, while the volatile fatty acids-to-microbial protein pathway 0.04 g/g VS and 91–362 €/ha•year.