Valorization of Hemp Stalk Waste Through Thermochemical Conversion for Energy and Electrical Applications

Abstract

The presented research aimed at finding new ways to value hemp by-products (stalks) from the cannabidiol industry through thermochemical conversion. Chemical and elemental composition of hemp biomass was investigated by successive chemical extractions and Scanning Electron Microscopy along with Energy-dispersive X-ray Spectroscopy. Proximate and elemental analyses completed the chemical characterization of the hemp biomass and its biochar. Thermogravimetric analysis of the hemp biomass allowed to understand its kinetic of decomposition during thermal conversion. The carbon structure and porosity of the biochar were assessed by Raman spectroscopy and CO2 gas adsorption. Properties of interest were the energy production measured through calorific values, and the electrical conductivity. Two ways of valorisation of the hemp biomass were clearly identified, depending mainly on the chosen pyrolysis temperature. Hemp biochar carbonized at 400–600°C were classified as lignocellulosic materials with a good potential for solid biofuel applications. Specifically, the resulting carbonized biochar presented low moisture content (below 2.50%) favourable for high fuel quality, low volatile matter (27.1–10.4%) likely to show lower particle matter emissions, limited ash content (6.8–9.8%) resulting in low risk of fouling issues during the combustion, high carbon content (73.8–86.8%) suggesting strong energy density, associated with high higher heating values (28.45–30.95 MJ kg−1). Hemp biochar carbonized at 800–1000 °C displayed interesting electrical conductivity, opening opportunities for its use in electrical purposes. The electrical conductivity was related to the evolution of the biochar microstructure (development of graphite-like structure and changes in microporosity) in regard with the thermochemical conversion process parameters. Graphical abstract

Effect of Biochar Addition on Mechanical Properties, Thermal Stability, and Water Resistance of Hemp-Polylactic Acid (PLA) Composites

“…Thus, the improvement in thermal resistance is due to the high cellulose content in hemp fibers. Indeed, Marrot et al [ 17 ] reported a 77–80% w /r w cellulose of the dry material. Thus, the improvement in thermal resistance is due to the high cellulose content in hemp fibers, which decomposition temperature range is higher than the PLA’s one.…”

“…BC recently emerged as filler in polymeric composites, including thermoplastics and thermosets [ 13 , 14 ]. The attractiveness of BC lies in its superior characteristics (depending on pyrolysis conditions), such as hydrophobicity [ 15 ], electrical conductivity [ 16 , 17 ], high surface area, and porosity [ 18 ].…”

A Robust Process to Produce Lignocellulosic Nanofibers from Corn Stover, Reed Canary Grass, and Industrial Hemp

“…Industrial hemp ( Cannabis sativa L.—IH) is a fast-growing, non-wood plant fiber crop with low water and nutrient requirements that grows in various environmental conditions [ 26 , 27 ]. While IH seeds are currently used for oil extraction, the remaining stalks (which represent about 70% of the plant’s dry weight) have been either used in low-value applications or have just been sent to waste [ 26 ].…”

“…Industrial hemp ( Cannabis sativa L.—IH) is a fast-growing, non-wood plant fiber crop with low water and nutrient requirements that grows in various environmental conditions [ 26 , 27 ]. While IH seeds are currently used for oil extraction, the remaining stalks (which represent about 70% of the plant’s dry weight) have been either used in low-value applications or have just been sent to waste [ 26 ]. Morphologically, IH stalks contain two types of fibers: bast (very long, about 10 to 20 times longer than fibers from hardwoods, softwoods, and agricultural residues) and core fibers (shorter fibers with similar physical characteristics to hardwood fibers) [ 25 , 28 ].…”

Fully bio‐based thermoset composites from UV curable prepregs: Vegetable oil acrylate impregnated hemp nanopaper

“…7 In addition, hemp is compatible with cold climates and produces relatively large yields, of which hemp stalks are still underutilized but full of exceptionally durable cellulose fibers. 8,9 Triglycerides (vegetable oils) have shown great potential for polymer production and have even yielded commercial products such as acrylated epoxidized soybean oil (AESO). 10 While direct application of oils is challenging, relatively simple modification methods are very efficient in turning them into reactive monomers.…”