Lignin–Cellulose Nanocrystals from Hemp Hurd as Light-Coloured Ultraviolet (UV) Functional Filler for Enhanced Performance of Polyvinyl Alcohol Nanocomposite Films

Lignin is a natural light-coloured ultraviolet (UV) absorber; however, conventional extraction processes usually darken its colour and could be detrimental to its UV-shielding ability. In this study, a sustainable way of fabricating lignin–cellulose nanocrystals (L-CNCs) from hemp hurd is proposed. A homogeneous morphology of the hemp particles was achieved by ball milling, and L-CNCs with high aspect ratio were obtained through mild acid hydrolysis on the ball-milled particles. The L-CNCs were used as filler in polyvinyl alcohol (PVA) film, which produced a light-coloured nanocomposite film with high UV-shielding ability and enhanced tensile properties: the absorption of UV at wavelength of 400 nm and transparency in the visible-light region at wavelength of 550 nm was 116 times and 70% higher than that of pure PVA, respectively. In addition to these advantages, the nanocomposite film showed a water vapour transmission property comparable with commercial food package film, indicating potential applications.

Can hemp hurd or paper mulch and biochar application improve weed management in matted-row strawberry production systems?

During 2015 and 2016, studies were conducted at Absaraka and Dickinson, North Dakota to evaluate the impacts of hemp (applied at 1156 m3 ha−1) and commercial paper mulch, as well as soil-applied biochar (applied at 11.25 m3 ha−1), on weed suppression and strawberry growth during the establishment year, and on weed suppression and strawberry yield during the production year, in a matted row production (MRP) system. During 2015, biochar influenced dry weed biomass only within the hemp mulch, with slightly more weed biomass associated with biochar application compared to zero biochar (3.1 vs 0.4 g m−2), suggesting that biochar may have increased weed germination and/or emergence from beneath hemp mulch. Biochar application also slightly increased soil pH, from 6.9 in non-amended soil to 7.0 in amended soil. Strawberry runner number during 2015 was greater in association with hemp or paper mulch compared to zero mulch (4.5 and 4.9 vs 2.4 runners plant −1, respectively). This result mirrored a similar differential in per berry mass across sites (7.6 and 7.4 vs 6.2 g berry −1 for hemp mulch, paper mulch and zero mulch, respectively). These results may be related to hemp and paper mulch reducing maximum soil temperatures during summer 2015. During the establishment year, both hemp and paper mulch suppressed weeds well compared to zero mulch, although at Absaraka hemp mulch provided slightly better weed suppression than paper mulch. During the production year, both mulches continued to suppress weeds compared to zero mulch at Dickinson. However, at Absaraka, only hemp mulch provided weed suppression compared to zero mulch, possibly because of faster paper degradation caused by greater numbers of large precipitation events and greater relative humidity at Absaraka compared to Dickinson. Weeds were removed from plots during 2015 to allow separation of weed suppression from other possible mulch impacts; therefore, yield data do not reveal striking differences among mulch treatments. Because previous research has demonstrated the impact of weed management during the establishment of strawberries in a matted row system, we concluded that hemp mulch may provide more durable weed suppression compared to paper mulch, which would increase strawberry yield protection in an MRP system. Material cost may be an issue for implementing hemp mulch, as hemp hurd cost was 25 times paper mulch at the application rates used in this study. However, hemp mulch could still be a beneficial option, especially for organic strawberry growers desiring a renewable and environmentally sound replacement for plastic mulch who are able to find affordable local sources of this material.

Valorization of Hemp Hurds as Bio-Sourced Additives in PLA-Based Biocomposites

Sourced from agricultural waste, hemp hurds are a low-cost renewable material with high stiffness; however, despite their potential to be used as low-cost filler in natural fiber reinforced polymer biocomposites, they are often discarded. In this study, the potential to add value to hemp hurds by incorporating them into poly(lactic acid) (PLA) biopolymer to form bio-based materials for packaging applications is investigated. However, as with many plant fibers, the inherent hydrophilicity of hemp hurds leads to inferior filler-matrix interfacial interactions, compromising the mechanical properties of the resulting biocomposites. In this study, two chemical treatments, alkaline (NaOH) and alkaline/peroxide (NaOH/H2O2) were employed to treat hemp hurds to improve their miscibility with poly(lactic acid) (PLA) for the formation of biocomposites. The effects of reinforcement content (5, 10, and 15 wt. %), chemical treatments (purely alkaline vs. alkaline/peroxide) and treatment cycles (1 and 3 cycles) on the mechanical and thermal properties of the biocomposites were investigated. The biocomposites of treated hemp hurd powder exhibited enhanced thermal stability in the temperature range commonly used to process PLA (130–180 °C). The biocomposites containing 15 wt. % hemp hurd powder prepared using a single-cycle alkaline/peroxide treatment (PLA/15APHH1) exhibited a Young’s modulus of 2674 MPa, which is 70% higher than that of neat PLA and 9.3% higher than that of biocomposites comprised of PLA containing the same wt. % of untreated hemp hurd powder (PLA/15UHH). Furthermore, the tensile strength of the PLA/15APHH1 biocomposite was found to be 62.6 MPa, which was 6.5% lower than that of neat PLA and 23% higher than that of the PLA/15UHH sample. The results suggest that the fabricated PLA/hemp hurd powder biocomposites have great potential to be utilized in green and sustainable packaging applications.

Combining Fiber Enzymatic Pretreatments and Coupling Agents to Improve Physical and Mechanical Properties of Hemp Hurd/Wood/Polypropylene Composite

Natural fiber/plastic composites combine the low density and excellent mechanical properties of the natural fiber with the flexibility and moisture resistance of the plastic to create materials tailored to specific applications in theory. Wood/plastic composites (WPC) are the most common products, but many other fibers are being explored for this purpose. Among the more common is hemp hurd. Natural fibers are hydrophilic materials and plastics are hydrophobic, therefore one problem with all of these products is the limited ability of the fiber to interact with the plastic to create a true composite. Thus, compatibilizers are often added to enhance interactions, but fiber pretreatments may also help improve compatibility. The effects of pectinase or cellulase pretreatment of wood/hemp fiber mixtures in combination with coupling agents were evaluated in polypropylene panels. Pretreatments with pectinase or cellulase were associated with reduced thickness swell (TS24h) as well as increased modulus of rupture and modulus of elasticity. Incorporation of 5.0% silane or 2.5% silane/2.5% titanate as a coupling agent further improved pectinase-treated panel properties, but was associated with diminished properties in cellulase treated fibers. Combinations of enzymatic pretreatment and coupling agents enhanced fiber/plastic interactions and improved flexural properties, but the effects varied with the enzyme or coupling agent employed. The results illustrate the potential for enhancing fiber/plastic interactions to produce improved composites.

Different Approaches to the Synthesis and Applications of Biomedical and Pharmaceutical Smart Biomaterials

In this study, two strategies were used to functionalize cellulose nanowhiskers. Firstly, by grafting its surface with β-cyclodextrin (βCD) for developing drug-nanocarrier. Secondly, by conjugating short polymer segments to its surface for reinforcing Poly(Ɛ-Caprolactone) (PCL), in order to develop nanocomposites with promoted properties suitable for regenerative medicine. In addition, the production and recovery of biodegradable bioplastics poly(3-hydroxybutyrate) (P(3HB)) from agro-industrial residues of hemp hurd biomass was also examined. In the first part, a drug-nanocarrier system based on βCD-grafted bacterial cellulose nanowhisker (BCNC-g-βCD) was developed as a prolonged drug release nanocarrier. Antibiotic Ciprofloxacin (CIP) and anticancer drugs; Doxorubicin (DOX) and Paclitaxel (PTX) were conjugated to BCNC-g-βCD as model drugs to form the drug-nanocarrier (BCNC-g-βCD-drug). Compared with un-grafted BCNC, the developed drug-nanocarrier showed significant increase in drug payloads from 495 ±4 to 810 ±7 µg/mg along with radical improvement in the drug release profiles. Initial burst releases was reduced significantly and prolonged and sustained release for (74.5–90%) of drug payload over 4–5.5 days were observed. In addition, an improved drug release performances were pragmatic in acidic pH of 6.4 that mimicked extracellular tumor cells. In vitro drug release data pointed to zero-order kinetic model with estimated zero-order release constants (K0) of 0.68, 0.74, and 0.79 µg drug/h (at pH 6.4, 37°C) for BCNC-g-βCD-CIP, BCNC-g-βCD-DOX and BCNC-g-βCD-PTX nanosystems, respectively. In the second part, the functionalized bacterial cellulose nanowhisker (BCNW-g-βCD-PCL2000) was synthesized. Reinforcing PCL matrix with 4 wt% of the functionalized nanowhisker resulted in bionanocomposite with promoted bulk properties. Compared to neat PCL, the obtained bionanocomposite showed 115% and 51% improvements in tensile strength and Young’s modulus, respectively; 20% increase in hydrophilicity; 7% increase in degradation rate; and 6% decrease in crystallinity. Gas foaming/combined particulate leaching technique is used to develop highly porous strutures having porosity of 86-95% and interconnected macropores with mean pore diameters of 250-420 µm. Porous scaffolds showed compression moduli values of 5.3-9.1 MPa in the range of cancellous bones. In the third part a dual-function PCL scaffold was fabricated. The envisioned drug-laden scaffold would provide adequate structural and mechanical supports for the newly regenerated tissues and simultaneously serve as localized drug delivery system. In this context, reinforced PCL with 4 wt% of BCNW-g-βCD-PCL2000 and 25 wt% of doxorubicin anticancer drug resulted in drugladen bionanocomposite of combined promoted bulk properties. Improvements of 165% and 107% in tensile strength and Young’s modulus, respectively; 31% in hydrophilicity; 10% in degradation rate; and 8°C increases in thermal stability. The obtained drug-laden porous scaffolds showed compressive moduli in the range of 7.2-12.3 MPa. In vitro drug releases fit the first-order release mechanism and occurred in a diffusion-controlled and sustained manner 60 days without obvious burst releases. The scaffolds will ultimately minimize systemic toxicities of drugs, lessen the number of dosing, and diminish the need for removal procedure. The forth study described prospective trials for greener production and extraction of the biodegradable bioplastics poly(3-hydroxybutyrate) P(3HB) from agro-industrial residues of hemp hurd biomass. Results showed that maximum hydrolysis yield of 72.4% was achieved by alkali pretreatment with 2% NaOH at 135°C for 60 min along with two-step enzymatic hydrolysis and ultrasonication. Total hydrolysate sugar concentration of 53.0 g/L was obtained. Under optimum conditions, total P(3HB) production of 13.4 g/L was achieved within 80 h of fermentation. Ultrasonic-assisted sodium dodecyl sulfate (SDS) has showed effectiveness as economic recovery method. It recovered bioplastics directly from the broth cell concentrate with P(3HB) content of 92%. Number average molecular weights (Mn) of recovered bioplastics were in the range of 150–270 kDa with polydispersity index (Mw/Mn) of 2.1–2.4.