Characterization and pretreatment of milled hemp (Cannabis sativa L.) fibers from high-cannabinoid type crops for biochemical conversion

The cannabidiol (CBD) market is a major driver of U.S. hemp (Cannabis sativa L.) production. High-CBD type hemp production results in large amounts of unused lignocellulosic biomass. Traditionally, bast and hurd fibers from industrial hemp types (fiber/grain) are separated via decortication, with the high-value bast fiber destined for textile applications and the hurd fibers used for various bio-composites and bio-based chemicals. Unlike stalks from industrial hemp types, high-CBD hemp stalks are often considered unfit for decortication. As a result, this material is typically milled such that the bast and hurd fibers are combined. There has been substantial interest in the use and development of these fiber mixtures for bio-based materials and replacement of petroleum-based chemicals. Little information, however, is available on the chemical properties of the mixed fiber compared to separated hurd fiber. This information is needed in order to identify the optimal use of this material, especially if the fiber is to be pretreated for enzymatic hydrolysis and downstream fermentation of the C5 and C6 sugars. The mixed fiber biomass from high-CBD hemp is also expected to closely resemble the biomass residues from other high-cannabinoid crop production, such as those from the recreational and medicinal Cannabis industries. Being able to find suitable value-added uses for the waste streams from these growing markets will be increasingly important to their economic success.