Hemp Growing

Among the 4 harvested industrial hemp products, diesel fuel consumption and fertilizer were the inputs that were most affected in the field subsystem and together ranged from 73 and 82% of the total impacts, while machinery upstream manufacturing accounted for a minor proportion of the requirements . These results were also confirmed by Zampori et al. who found that fertilization is one of the main impacting processes in industrial hemp cultivation and harvest. Another energy and environmental aspect to emphasize is related to irrigation water. The cultivation of industrial hemp in Mediterranean climates, with low rainfall during the growing season, causes irrigation practices to be a fundamental requirement. This practice was included in this study, where the water sources at both experimental sites came from pressurized irrigation networks with negligible direct energy requirements. Moreover, as already stated, industrial hemp cultivation in southern Mediterranean conditions requires higher irrigation volumes, in contrast to northern environments, but has lower water requirements than other specialized crops, such as maize, that are commonly utilized in ADPs. The industrial hemp seed oils that were obtained from plants cultivated in contaminated soil can be used for nonfood products, such as oil, to revive fine furniture woods and in the biodiesel industry. In fact, biodiesel is one of the most commonly accepted complementary fuels for diesel engines, where in recent years, the cost and competition with the food sector have been decreased by using nonedible feedstock . Another application of nonedible oil has been proven by QuilesCarrillo et al., who discussed the use of maleinized industrial hemp seed oil to reduce the intrinsic brittleness of polylactide materials without compromising their mechanical resistance and to construct toughened biopolymer pieces, plant benches which can find interesting applications in, for instance, rigid packaging.

The AD subsystem allowed us to explore the energy and environmental benefits of using the industrial hemp biomass that was obtained from contaminated soil for biogas production while avoiding secondary pollution. The digestates were modeled to be dewatered by using the heat from the CHP unit and then incinerated in a BFPP for electricity production. This solution, because of the reduction in the biomass to be disposed of in authorized plants, enables us to reduce the disposal costs and to obtain energy from renewable sources. To the authors’ knowledge, the use of industrial hemp as feedstock for ADP has been well discussed in the scientific literature; in contrast, the use of HM-contaminated industrial hemp biomass as feedstock for ADPs is absent. A recent review indicated that industrial hemp biomass is a suitable crop for AD applications with high biogas production yields. Plants that are obtained in the phytostabilization of trace element-contaminated soil may affect biomass biodegradability, while HMs affect the physiological and biotechnological environments in AD. In fact, HMs interact with the microbial community and affect biogas production in AD processes, where trace HMs can promote biogas and methane production, while excessive HMs cause inhibition. Lee et al.demonstrated that the inhibition derived from HM-contaminated biomass was negligible, consequently, AD seems to be feasible for the disposal of HM-containing crop residues from phytoremediation sites. However, the release characteristics and fates of HMs should be carefully considered to predict the stability of the AD process for HM-containing biomass. Regarding BFPPs, greater energy and environmental benefits might be achieved by using the waste heat that is generated by these plants. As reported by BEN, most of the heat derived from cogeneration plants is used in the same facilities, while a minor proportion is used in district heating networks to provide heating services to the domestic sector. Instead of dispersing the waste heat that is generated by thermoelectric power plants into the atmosphere, these plants might convey this heat for useful consumption, which would thus avoid burning fossil fuels that would otherwise be necessary to be consumed to provide the same heating service.

The disposal of biomass ash represents a point of debate in environmental studies. The ash yields from biomass combustion range from 0.4 to 6%, and the ash compositions vary depending on the nature of the incinerated biomass. For this reason, it is important to individually characterize each type of biomass ash prior to finding an appropriate utilization approach. Biomass ash disposal has been found to be an influencing factor in the bioenergy and biowaste supply chain, while other studies have found that the contributions of the final disposal of biomass ash were not significant or were excluded from the study boundaries. Biomass ash is free of nitrogen and contains large amounts of micro- and macronutrients that are highly suitable for mineral soil amendments, the biological reclamation of degraded areas and dewatering sewage sludge. In addition, a recent review by Cui et al. emphasized that the incineration of contaminated biomass in modern incineration systems represents a technologically and economically feasible approach for treating hyperaccumulator plants, where ash residues could be pretreated and employed to produce construction materials and high-density glass-ceramics. Modern incineration systems could employ environmentally sound technologies that would perform better than pyrolysis and gasification-melting plants because of several benefits of flue gas cleaning, ash recycling, and the combined heat and power cycle. Moreover, these authors found that the efficient management of metals and bottom ash may decrease the volumes of waste landfills and reduce the consumption of raw materials. Finally, these results identify the great potential of using contaminated areas for bioenergy production while minimizing the exploitation of natural resources and avoiding pollutant emissions into the environment. As suggested by Pulighe et al. , the cultivation of marginal lands for bioenergy production provides ample opportunities to conduct successful feedstock production in unmanaged areas. Currently, HM contaminated soils are mostly unproductive and require expensive and long-term remediation programs to be turned into productive areas . Recently, the use of natural fibers has increased considerably due to its availability, low-density and price compared to synthetic fibers. Those factors are responsible for the apparition of a new polymer science and engineering research.

Natural fibers were introduced with the intention of yielding lighter composites, coupled with lower costs, compared to the fiber glass reinforced polymer composites. Natural fibers have a lower density than that of glass fiber , which ensures the production of lighter composites. Conventional petroleum based epoxy resin, polyurethane , are used extensively with natural fibers, such as hemp, jute, sisal, and kenaf.Recently, the rapidly expanding use of composite components in construction, sports, leisure, and other mass production industries, has been focused on sustainable and renewable reinforced composites. Building insulation is one of the most applications of this material, mechanical and thermal properties are the obvious needs in this area. Physical properties of polyurethane-based composites have been widely studied. Hadjadj et al. demonstrated that Young’s modulus of PU-Alfa fibers composite improved linearly with the embedded cellulose content, it increase by 250%–700% when the fiber reinforcement is raised from 5% to 30%. Radzi et al. have also studied the influence of the addition of Roselle fiber on the mechanical and thermal properties of polyurethane composites they concluded that the tensile and fluxal strength increase with fiber contents, 40 wt% fiber content showed the highest strength. Oushabi et al. studied the effect of polyurethane reinforced by date palm waste, they showed that this reinforcement affects the mechanical properties of the resulting composite, the thermal conductivity of prepared composite makes it possible to consider them as competitive for the development of effective, inexpensive insulating materials and safe. Silva et al. studied the influence of Eucalyptus grandis fibers on rigid PUs and found that the addition of 16% natural fiber drastically increased their mechanical strength and thermal conductivity. Hemp fiber is one of important natural fibers used in industrial areas, which has relatively short cropping cycle and can be easily grown in a large array of environments. In addition, hemp characterized by a tensile strength of up to 1110 MPa is one of the strongest fibers among all bast fibers. There are previous studies reporting on mechanical properties of PU-hemp fibers composites they concluded that treated hemp fibers with alkaline, silane or acetyl solutions can improve tensile and flexural properties of composites. Several works are interested in the mechanical behavior of polyurethane- natural fiber composites, but few have studied the effect of this reinforcement on the thermal conductivity. The aim of this paper is to study the properties of hemp fiber reinforced composites with differential fiber contents . Mechanical, hygroscopic and thermal conductivity, of HF/PU composites were examined.

During their life cycle service, rolling bench the composites materials are often exposed, for long periods, to humid environments. However, moisture generates heterogeneous internal stress fields in this type of material, which leads to the changes in thermal and mechanical properties. Thus, it is interesting to predict the absorption of water for all formulations in order to estimate their sustainability. Water uptake effects on thermal conductivity have been studied by they reported that the thermal conductivity of composite materials increases with volumetric water content. The origin of this increase is due to the saturation in water, in this state the water occupies the open pores of the materials.The water uptake can also affect the mechanical properties of composite materials; the water molecules change the structure and properties of the fibers, matrix and the interface between them, leading to the loss of compatibilization between the fibers and the matrix, to the chain reorientation and shrinkage of matrix also lead to the degradation of natural fibers by a hydrolysis mechanism. All these factors led to decrease mechanical properties of the composite. The water absorption amount was calculated by the weight difference between the samples exposed to water and the dried samples using the following Eq1. Water absorbed percentages in terms of a time for all samples are showed in Fig. 6. The same behavior was observed for all samples, composite materials absorbed water in two stages, and during the first stage the speed of absorption is very fast reaching a certain value, then slows and approaches saturation after prolonged time following a Fickian diffusion process. Both the initial rate of water absorption and the maximum water uptake increase for all hemp fiber composites samples as the fiber content increases. From sorption, diffusion and permeability coefficients values shown in Table 2 it is clear that the polyurethane absorbs less distilled water than prepared composites due to its closed cell structure which prevents water absorption and moisture storage. The incorporation of hemp fibers, highly hydrophilic, increase greatly the water content that can be retained by the composite materials, this behavior has been observed in other works of hemp fibers and polymer matrix composites. Water absorption increase at higher fiber content, the composite PU 30%, has the largest water uptake and permeability coefficient, which limits the use of these renewable resources to high percentages exceeding 25%.The performance of materials is always presented in terms of their mechanical characteristics, such as tensile properties, flexural properties, compression properties, impact properties and wear behavior. It is evident from Fig. 7 that all composites showed a ductile behavior, The properties of the polyurethanes vary considerably with the fiber content, reinforced composites with hemp fibers showed better tensile strength than the polymer matrix. The tensile strength of composites has been found to increase with hemp fibers reinforcement. Composites with 15% loading exhibit maximum tensile strength, followed by 10%, 5%, 20%, 25% and 30% loadings. The failure of reinforced composites under tensile load could be due to breaking of cellulosic fibers at the weaker point followed by further propagation under the applied load that is transferred to adjacent fibers by the matrix, leading to complete rupture of the composites. From the value of Young’s modulus and tensile strength reported in Table 3, it is clearly asserted that there is a gradual decrease in the strength when increasing the percentage of the hemp fibers up to 20%. The tensile strength observed is better at 15% hemp fiber. The flexural strength results of hemp fiber composites follow the same trends obtained in tensile strength tests. Table 4 shows that the flexural properties increase up to 15% of fiber, and then keep this increase, after 20% of fiber we observed also the deterioration of the mechanical properties.

The alkali treatment increased slightly the density of the reinforced mortar.No significant difference could be noticed between the bulk densities of all mortar groups after wet/dry cycles compared to those of their non-aged counterparts.The difference of NaOH concentration by the fibres treatment does not significantly influence the physical properties of the fibre reinforced fly ash-based alkali-activated mortars.The reason for that is that even the lowest NaOH concentration was enough to separate the fibres from a fibre bundle.The increased NaOH concentration does not lead to more efficient fibres separation.This leads to no difference by the composites mixing and leads to similar composites structure formation.After the addition of the fibres,the compressive strength of the mortar decreases.It can be seen that at the age of 28 days,46% higher compressive strength is achieved in the plain mortar than in the non-treated fibre reinforced one.The addition of fibres leads to increased porosity and decreased density ,which consequently leads to a lower strength of the mortar.However,since the alkali treatment of fibres refines the fibre mortar’s pore structure,lowers the total pore volume and slightly increases the density of fibrereinforced mortars ,it consequently results in increasing their compressive strength.Additionally,the alkali treatment eliminates the fibrous filaments on the surface of hemp fibres as well as cleans the surface and separates the fibre bundles into fibrils ,which results in a better fibre dispersion within the matrix.Thisprovides better homogeneity of the composite,which in turn results in enhanced compressive strength.The concentration of the sodium itself in the fibres treatment proved to have no significant influence on the compressive strength of mortars.A similar trend but less pronounced was reported in fibre reinforced cementitious mortars after the fibres were treated with sodium hydroxide solutions.Jo et al.showed that 5 mm-long jute fibre treated with 0.5% sodium hydroxide increased the compressive strength of the fibre reinforced cement-based mortar by ca.5%.Yan et al.used 50 mm-long coir fibre to reinforce the cement-based specimens.After the fibre treatment with 5% sodium hydroxide solution,the compressive strength increased by only 0.8%.After the wet/dry cycles,cannabis grow racks the plain mortar shows 75% higher compressive strength than non-treated fibre reinforced mortar.

The drop of the strength after the fibres’ addition is related to the higher porosity of the fibre reinforced mortar.In addition to this,the hemp fibres are hydrophilic,so during the wet/dry cycles,they absorb water and swell.This can introduce micro-cracks in the matrix and lead to fibre–matrix debonding,thus preventing an optimal stress transfer within the matrix.However,the alkali-treated fibres significantly reduce the strength loss.It is shown that up to 50% higher compressive strength of the fibre reinforced mortar could be achieved after the wet/dry cycles when fibres are previously treated with 6% sodium hydroxide.Even more important is that 6% sodium hydroxide-treated fibre reinforced mortars experienced no loss of compressive strength after the wet/dry cycles.Without the fibre treatment,fibrereinforced mortars lose 20% of their strength when compared the result after wet/dry cycles to the non-aged mortar’ result.TG-DTA plots of the mortar samples are illustrated in Figs.13 and 14.The bound water in the gel-like binder phase and the heat of reaction required for its decomposition are reported in Table 5.A higher heat of reaction in the plain mortar compared to the fibre reinforced mortar groups indicates a larger amount and a better-incorporated binder phase in the formed alkali-activated matrix,characterized by a binding potential.Mortars show a broad endothermic peak in the temperature range of 100 ◦C to 300 ◦C,especially those without hemp fibres.The observed weight losses can be related to the bound water loss.It is shown that there is more bound water in the plain mortar than in the fibre reinforced mortars.This could be an indicator of the pore sizes of the binder gel since the bound water is tightly held only in very small pores.The more bound water,the more small-size pores appear.This correlates to the porosity obtained by the MIP.The plain mortar results in a more pronounced amount of the smallest pores than fibre reinforced mortars.However,the alkali-treated fibre reinforced mortars result in slightly enhanced bounded water content in their gel-like matrices and the more optimal pore sizes distribution than the nontreated fibre reinforced mortar.This consequently leads to their higher compressive strength.The flexural strength of the mortars follows the same trend as their compressive strength.The addition of fibres decreases the flexural strength of mortars.The flexural strength of the plain mortar is 34% higher than the one of non-treated fibre-reinforced mortar,tested at the age of 28 days.This is the result of increased porosity and decreased density after fibres addition,which consequently leads to a lower strength of the mortar.Even though the flexural strength is mostly influenced by the matrix itself,it is noticed that with the fibre treatment,the flexural strength of the fibre reinforced mortar increases.The difference in the concentrations of the applied sodium hydroxide influenced only slightly the flexural strengths of the mortars.A similar trend but less pronounced was reported in fibre reinforced cementitious mortars after the fibres were treated with sodium hydroxide solutions.Jo et al.showed that 5 mm-long jute fibre when treated with 0.5% sodium hydroxide,increased the flexural strengths of fibre reinforced cementbased mortars by 3.6%.Yan et al.used 50 mm-long coir fibre to reinforce the cementbased specimens.After fibre treatment with 5% sodium hydroxide solution,the flexural strength increased by 6.5%.After the wet/dry cycles,the plain mortar shows 46% higher flexural strength than the non-treated fibre reinforced mortar.This results from the hydrophilic nature of hemp fibres and their ability to absorb water and swell during wet/dry cycles.This could cause microcracks in the matrix and lead to fibre–matrix debonding,which decreases the flexural strength of a mortar.

The alkali-treated fibres could reduce the strength loss,by reducing the water absorption capacity of the fibres themselves.On average 23% higher flexural strengths are achieved after the wet/dry cycles.The flexural strength of all mortars after wet/dry cycles was on average 33% lower in comparison to their non-aged counterparts.In the fibre reinforced mortar groups,this difference is even lower in the case of 6%- and 9% sodium hydroxide-treated fibre reinforced mortar.These mortar groups show almost the same flexural strength drop as plain mortars.The most important contribution of fibre reinforcement in the mortar matrix is in the prolongation of crack initiation in the pre-cracked state and in the slowdown of crack propagation in the cracked state which results in enhanced energy absorption capacity under flexure.The presence of fibres in the matrix changes the mortars’ behaviour from quasi-brittle toward a more ductile one dependent on the type,geometry and dosage of the fibres.Plain mortars have almost no deformation capacity after the maximal flexural force is reached,indicating a negligible energy absorption capacity in the post-peak region.On the other hand,hemp fibre reinforced mortars have a significantly higher deformation capacity in the post-peak region,indicating a much higher energy absorption capacity than plain mortar.With the fibres treatment the energy absorption capacity can be increased even more.The fibre-bundles separation leads to better fibre dispersion through the matrix.In addition to this,the fibres treatment increases the roughness of the fibre surface resulting in a stronger fibre–matrix bond,which could be seen by the higher number of matrix particles attached to the treated fibres after 3PBT.The alkali pretreatment of hemp fibres leads to their surface fraying effect due to the degradation of the hemp components – hemicellulose and lignin.This chemical process could cause an improvement in interaction at the interface of the binding alkali-activated matrix and hemp fibers.At the age of 28 days,3% sodium hydroxide-treated fibre reinforced mortar has a higher energy absorption capacity than the nontreated fibre reinforced mortar.The further increase of the sodium hydroxide concentration in the fibres’ treatment slightly decreases a mortar’s energy absorption capacity ,keeping it still higher than the one of the non-treated fibre reinforced mortar.The enhancement of the energy absorption capacity with alkali treatment of fibres was also reported in cementitious materials.Jo et al. showed that the energy absorption of the jute fibre reinforced cement-based mortar increased by 6.5% when the fibres were treated with 0.5% sodium hydroxide solution,whereas Yan et al.reported an increase by 8.7% of the coir fibre reinforced cement-based mortar’s energy absorption when the fibres were previously treated with 5% sodium hydroxide solution.

When specimens undergo wet/dry cycles,the results show that nontreated fibre reinforced mortar has 343% higher energy absorption capacity than plain mortar.In the case of alkali-treated fibres,the energy absorption capacity of the non-treated fibre reinforced mortar increases even more,i.e.by 8%,19% and 15% for 3%-,6%- and 9% sodium hydroxide-treated fibre reinforced mortars,respectively.It seems that the higher concentration of the sodium hydroxide results in less hemicellulose in the fibres which leads to lower water absorption.This prevents the swelling of fibres,which causes micro-cracks in the matrix around the fibres and leads to fibre–matrix debonding.When comparing the results of the specimens after wet/dry cycles to those tested at the age of 28 days,it is seen that the addition of nontreated fibres to the matrix can significantly reduce the decrease of the energy absorption capacity of the plain mortar.With the alkali-treated fibres,cannabis grow system the decrease could be reduced even more.The energy absorption capacity of the mortar shows the lowest decrease after the wet/dry cycles when the fibres are treated with 9% sodium hydroxide.The fibres in that case reduce their water absorption capacity mostly.Besides,it could be seen that 3% sodium hydroxide treated fibre reinforced mortar before the wet/dry cycles has a higher percentage share of the energy absorption capacity in the later post-peak part of the force–displacement curve than after the wet/dry cycles.On the other hand,9% sodium hydroxide treated fibre reinforced mortar contributes more to the percentage share of energy absorption capacity in the post-peak part after the wet/dry cycles than it does before the aging.The reason could be that after the heat during the drying cycles,mortars continue with the further development of their system and increase the formation of mineral products while decreasing the amount of entrained pores.Including the higher fibres roughness after 3% sodium hydroxide treatment,this could lead to strong fibre–matrix bonds.The strong fibre–matrix bond leads consequently to a more pronounced fibres break after the failure of the matrix,which does not increase the post-peak part of the force–displacement curves.Therefore,in terms of the energy absorption capacity of the mortars when exposed to wet/dry cycles,9% sodium hydroxide concentration is considered as the most optimal fibre treatment.Hemp is an industrial crop that is commonly used in the textile,pharmaceutical,and paper industries.Hemp seeds are a by-product of hemp processing and contain 25–30% oil,20–30% protein and other nutritional substances.

Hemp seed oil contains more than 80% unsaturated fatty acids and a high content of functional components,including linoleic acid ,linolenic acid and other essential fatty acids,as well as tocopherols,vitamin A,minerals,etc.,which have a positive impact on cardiovascular,mental and immune diseases and can be added to foods as functional fats.HSO contains low levels of the psychoactive compound tetrahydrocannabinol  in compliance with European Union and American standards.THC is a polyphenol with high antioxidant properties,which enhances the antioxidant properties of the product.Therefore,encapsulating HSO in emulsions can improve its bioavailability,avoid oxidation reactions,and broaden its application scope.Mikulcov´ a et al.prepared HSO oil-in-water emulsion with emulsifier Tween to improve its stability and antimicrobial activity.Jarzebski et al.used pea protein as a stabilizer for HSO emulsions and the emulsions showed good results in terms of particle size and encapsulation efficiency.Proteins with amphiphilic properties can be used as emulsifiers,and similarly,hemp seed proteins can be used to stabilize HSO emulsions.Compared to common high-quality proteins ,HPI is hypoallergenic,highly digestibility,has a good composition of essential amino acids.This means a more nutritionally superior amino acid pattern.In addition,its solubility is low,and its emulsification ability can be affected by external factors such as pH during treatment.HPI-stabilized sunflower oil emulsions were prepared by Dapˇcevi´cHadnađevd et al.It was found that the interaction between HPIs affected the transient flocculation network and contributed to the emulsion stabilization,and the emulsification activity of HPIs was similar to the protein solubility curve.Tang et al.have compared the functional properties of different proteins,where HPI has lower emulsifying activity and emulsifying stability than soybean protein,rice protein and pea protein.Therefore,external more energy efficient means or devices are needed to assist in the preparation of stable emulsions,such as ultrasonic,microwave,microjet,etc.High-intensity ultrasonic is an emerging processing method with frequencies typically in the range of 20–100 kHz and intensities in the range of 10–1000 W/cm2.

A first set of trials are performed at the industrial scale first,using flax dedicated machines and their associated settings to establish a reference.Then,a laboratory scale scutching and hackling equipment was used to investigate/optimise the scutching and hackling process parameters to improve the quantities of fibres and maximise their performances.Projections of long fibre yields in conjunction to dew-retted dry hemp stem yields are also given and permit to discuss the future of a complementary value chain in flax territories.A lab scale scutching/hackling extraction device was used.It,was used to separate the different plant fractions contained in the hemp stems with the main objective to obtain the long line fibres analysed in this study.The hemp stems are stabilised before testing at 65 % relative humidity and 23 ◦C.This lab-scale scutching/hackling device is composed of three distinct modules.The first one has the function of breaking the wooden part of the stems and allowing a first extraction of the shives and the dust.It is composed of a set of three pairs of corrugated rollers with adjustable distance between centres and speed of rotation.The material obtained is then automatically transported to a scutching system.It consists of two rotating turbines,which rotate in opposite direction to each other.Their role is to beat the fibres and to remove the shives still tied to the fibres.The residence time in the scutching module and the turbine speed are adjustable.Finally,the fibres are subjected to a progressive hackling stage to align the fibres and reduce technical fibre diameter.The hackles or combs are mounted on two rotating belts that can be adjusted in speed.The translation speed of the fibre is also adjustable.Stems from the retted and un-retted batches are subjected to extraction by scutching and hackling using the lab scale device.An additional part of the fibres from the dew retted stems were extracted using an industrial scale Depoortere scutching device and a Linimpianti hackling machine located at the “Terre de Lin” company.

Fig.1 shows the different steps of the industrial scutching and hackling of hemp stems.This scutching machine is composed of two distinct devices: a breaking system composed of a succession of horizontal fluted rollers and a beating stage which consists of successive pairs of rotating turbines,grow cannabis with each turbine rotating in opposite direction.The scutching machines are designed to process more than one ton of flax straw per h and globally deliver 250 kg of long line fibres.The hackling machine is a Linimpianti type equipment that was designed to process about 80 kg/h of scutched fibres.It is a fast and high production rate if one compares to traditional Mackie type machines which process globally up to 40 kg/h.For hemp,different settings were specifically applied to the scutching breaking and beating steps,but still with a high extraction speed,close to the one used for flax straw.The extraction parameters chosen for our device were optimised so that to obtain large quantities in mass of hackled long line fibres.Gentle extraction conditions have been applied by the lab-scale device with a low transfer speed during breaking and a low turbine rotation speed during scutching.Globally,a reduction of the transfer speed by 300 % and the turbine rotation speed by 400 % is applied in comparison to what is classically used in industrial scutching facilities for flax.As a result,some of the shives remain after the scutching stage,on the contrary to what is observed during industrial scutching.The type of combs and the hackling machine design offers the possibility to remove this wood without difficulty and to obtain clean long line fibres at the end of extraction.Following the stage of hackling and the realisation of a continuous sliver at the end of this process,the large count sliver is submitted to six drawing stages where the linear mass of the sliver decreases in our case up to a linear mass of about 150 tex depending on the settings.The used apparatus is a lab scale drawing system.This device mimics,at a reduced scale,the six drawing/doubling stages used in the flax spinning industry to prepare the slivers into rovings that will be used at the spinning stage.During the different stages of this process,six parallel flax dedicated systems using pin drive devices to bring the slivers and a wooden wheel to perform the drawing were used.This type of drawing system is also called “gill drawing system”.perform the different drawing operations.

During this stage,the sliver mass is reduced but it is also homogenised as between each drawing stage,six drawn slivers are each time grouped together before the following drawing.During these operations,the technical fibre diameter is also reduced when the technical fibres are pulled from the Gill system pins.The fibre diameter obtained at the end of the extraction and preparation processes was therefore investigated and compared for different batches at this stage.After processing the hemp stems through the various modules of the lab scale scutching hackling extraction device,several plant fractions are obtained.The shives,which are the woody part of the stems,can be separated from the dust generated during the extraction process and from the long line fibres and shorter fibres,also called tows.Thus,the by-products obtained at the output of each module are manually separated and weighed in order to determine the impact of the different extraction steps on each of the plant fractions as well as the yields.The study of the impact of the modules on the losses of the plant fractions is important in order to know which elements should be improved to increase the quantity and quality of the fibres.Fibre yield is computed at the end of the industrial scutching and hackling equipment.In order to investigate the impact of the different extraction steps on the mechanical and physical properties of the long line fibre,single elementary fibres are extracted after each module.Fibres are tested in tension and the evolution of fibre surface defect is investigated.The results obtained are compared to the initial potential of the material prior to any mechanical extraction.In the study of the industrial extraction of hemp fibres,fibres could only be collected after the scutching and hackling modules.To determine the initial mechanical potential of the elementary hemp fibres,prior to any mechanical extraction,fibres are manually extracted.To reach this objective,sections of stems are randomly taken and the bast peeled by hand.The elementary fibres are then carefully separated from the bast after soaking them in distilled water for about 10 s as specified in the NF 25-501-2 standard.Fibre samples were also taken after each extraction module of the lab scale scutching/hackling device.Thirty elementary fibres were then extracted from each batch to determine the impact of the various stages of the process on the mechanical properties of the fibres.The number of defects,as well as the morphological and mechanical properties of the fibres were evaluated.The main defects that can be observed on the surface of the fibres are kink bands which can be examined under polarized light as shown,for example,by Baley or Thygesen.

Kink bands are among the defects that can be visible on the surface of the fibres and are expected to be zones of weakness for the fibres as cracks were shown to preferably initiate from these zones.They can come from a disorientation of the cellulose fibrils due to some compression or bending loads.The number of kink bands on the surface of thirty elementary fibres for each batch is counted after observation with an optical microscope under polarized light and over a distance of 330 μm.In addition,the area of each of these kink bands is also determined,using ImageJ software following a manual identification of each kink band.The surface tool permits computing the area of the identified defects.2.7.2.Determination of the cross-sectional areas of the elementary fibres prior to tensile test The elementary fibres extracted from each batch are glued at each end to plastic tabs with a light-sensitive glue to prevent the fibre slipping during the tensile test.A gauge length of 12 mm is taken for tensile tests.The measurement of fibre cross-sections is carried out using a device manufactured by the company Dia-Stron called the Fibre Dimensional Analysis System and controlled by the UV Win software also developed by the company.This type of device permits to accurately determine the diameters of the fibres using an “automated laser scanning” method based on the light shadow technique performed using a high-precision laser source and photodetector.The fibres mounted on plastic tabs are positioned in the rotating jaws of the FDAS module and held in position by a pneumatic system.By 360 ◦ rotation of the jaws,the diameter of the fibre is measured over its entire circumference locally.The fibre is then translated and another part of the fibre is scanned over its whole circumference again.This operation can be repeated over the entire length of the sample.In this study,ten measurements are distributed over the 12 mm length of the gauge.As the fibre is rotating,the projected diameters are recorded and the maximum and minimum diameters are extracted to determine the fibre cross section using an elliptical model as recommended for technical fibres by who observed that this approach permits obtaining cross section measurements with a higher accuracy than with other models such as the circular model recommended by the NF 25-501-2 standard.This is due to the fact that hemp fibres are not circular.The measurements are carried out with an accuracy of 0.01 μm.A more detailed description of the device is available in Gr´egoire et al..Tensile tests are carried out on thirty elementary fibres from each batch.The device to apply the tension on the individual fibre was developed by the Dia-Stron,company.This is an automated high-precision extensometer which is equipped with a ±20 N load cell.Displacement is achieved using a step by step motor which permits to control the displacement with an accuracy of 1 μm.This makes the device suitable for fibre breaks with low levels of deformation.

The tests are carried out using a displacement speed of 0.0167 mm/s and a break threshold value of 5 gmf  as recommended by the NF T25-501-2 standard.The deformation selected for Modulus of elasticity corresponds to the one of the Young’s modulus,indoor cannabis grow system at the beginning of the stress-strain curve.The “fineness” of the fibre bundles is determined using a lab scale type device based on a laser scan technology proposed by Itecinnovation company.It consists in cutting the fibres in short length with a guillotine and dispersing them in an alcoholic liquid to prevent their swelling.Fibres are placed in a fluid flow and they are scanned by a laser: when a laser beam illuminates a fibre,a shadow appears on the photodetector.This area is directly proportional to the fibre diameter if one assumes that the fibres are cylindrical.This device,originally developed for wool fibres was modified by the manufacturer and adapted to bast fibres.This device was available at the Terre de Lin company premises.The tests were carried out on batches of 1000 fibres and a distribution can be obtained.The extraction of dew-retted hemp stems on industrial facilities,with process parameters not optimised for hemp,resulted in fibre yields of 9.15 % after scutching and 5.11 % after hackling.After hackling,the long line fibre mass represents in this case only 17 % of the initial fibre mass in the stem.The feed and beating speeds in the industrial scutching module are the ones generally used on flax.These process parameters appear to be un-adapted as very large quantities of fibres fall in the tows.After analysis,one can observe that a very large part of the scutching tow fibres are long line fibres.Scutching tows were taken randomly during the industrial scutching process right below the machines.One can observe in Fig.2a that a large amount of fibre is present.It contributes to about 50 % of the mixture mass.In Fig.2b,the tows,collected at a different moment contain in a vast majority long line fibre.A more complete analysis of the tows,with a large number of collected samples would be necessary to characterise the amounts of long line,short fibres and shives contained in the scutching tows.One can,however,observe that the mass of fibre is very large and can be represented by large quantities of long line fibres that should not fall in the tows.Different hypothesis can be formulated to explain this unwanted phenomenon.The first one is the use of too aggressive process parameters as,on the contrary to what was expected,hemp requires lower compression and beating loads than an equivalent mass of flax.

Field experiments were conducted in years 2014–2018 on the lignite post-mining area close to Kazimierz Biskupi province Wielkopolska, Poland. The research was financially supported by European Comission LIFE + grant LIFE11ENV/PL/445 and by National Fund for Environmental Protection and Water Management in Warsaw granted to the Institute of Natural Fibres and Medicinal Plants. Before agronomic treatments could be conducted in selected experimental field, they had to be cleared of volunteer weeds and bushes as well as stones. The number of stones made initially the work on the field impossible. After removing the stones, agrotechnical works were carried out, which included disc-harrowing of the field and plowing followed by pre-sowing tillage and application of lime in the dose of 0.25 tons/ha. Liming of the field was carried out only in the first year of the project. Every year mineral fertilization was carried out in accordance with the fertilization plan: nitrogen fertilization at a dose of 150 kg N/ha, phosphorus fertilization at a dose of 150 kg P2O5/ha and potassium fertilization at the dose of 215 kg K/ha. Phosphorus and potassium fertilizers were applied in autumn and nitrogen in spring before sowing of hemp. Every year in October hemp was mowed. Mowing was conducted using a mower pulled by the tractor, equipped with three knives cutting the stem into three sections. This facilitated later plowing the biomass down. Working width of the mower was 4 m and it was able to mow 3− 4 ha/h. In November, plant residues were plowed with 30 cm deep plowing. The costs of all agronomic treatments were estimated at 660 euro per hectar per year. Samples for soil tests were collected annually before the commencement of spring agrotechnical treatments with the use of a soil auger. The field was divided into four sections, five samples were taken from each section. Laboratory tests were performed using accepted Polish standards . Phosphorus and potassium were extracted from soil using Egner-Riehm method and then phosphorus was determined by spectrophotometric method and potassium by flame photometry .

Magnesium was extracted with 0.0125 M CaCl2 solution and determined by atomic absorption spectrometry . The soil pH was determined in 1 N KCl. Micronutrients were extracted with 1 N HCl and manganese, zinc and copper were determined by atomic absorption spectrometry while boron by spectrophotometry . The presented weather pattern data is from the Weather Station in Konin . In the years of experiment the average temperatures during hemp growth season differed only a little with the exception of 2018 – the warmest year in the period of plants emergency. Precipitation in 2017 was significantly higher than in the remaining years of the experiment. Especially June and July 2017 were characterized by a lot of rainfall. The reclaimed layer was very wet due to its limited water permeability. Frequent rainfall had largely suffocated the cultivated hemp. Cannabis grow system plants died in many places due to the lack of oxygen in the soil layer, which was displaced by water . The height of the plants often did not exceed 1 m at that year. Such unfavorable weather conditions led to a reduction in the yield of plants. The results were evaluated statistically with the R statistical software version 4.0.5 . ANOVA tests were used to test main effects of recultivation year. The data from all years were combined and analysed post hoc with Fisher’s LSD test from agricolae package at a significance level α = 0.05. Agrotechnical procedures related to reclamation of the experimental field started in 2013. They consisted of clearing the field of stones, sowing lime and PK fertilization. The aforementioned treatments were designed to initiate the plot reconstruction and preparation for the planned vegetation treatment. The soil depletion with previously conducted industrial activity resulted in low hemp yielding in the first year of the experiment. The average hemp biomass yield was only 1.6 tons/ha . Already in the second year of the project, the annual incorporation of biomass from the first year led to the activation of the soil and a jump of the yield of hemp biomass to 5.3 tons/ha , followed by 5.9 tons/ha in 2016. The highest yield of 6.3 tons/ha was obtained in the last year of experiment. This growth was also influenced by favorable weather conditions favoring the development of the plants in 2018. The increase of the hemp yield was the result of the increase of the plants heigh and the straw width . In the first year of the experiment the average plants heigh was only 56 cm, while on the second year it was higher by 236 % and in 2016 reached the average height of 193 cm.

The straw width on the second and third year of experiment was 3 times bigger than in 2014 . In 2017, hemp crop suffered due to long-lasting intense rainfall. A large amount of precipitation in the period immediately after emergence led to the loss of many plants. It was reported that too much available moisture can limit production or cause failure, particularly in low lying and poorly drained fields . In the case of the reclaimed minesoil, due to the compact, impermeable recultivated layer, even slight rainfall led to the formation of large water stalls . The standing water displaced oxygen from the soil which led to the suffocation of many plants. This lead to the low hemp yield of 3,5 tons/ha and low and thin plants. Every year, the hemp biomass obtained was plowed in, enriching the soil with nutrients. This affected the level of humus in the reclaimed soil. The 2014 yield after plowing in had an impact on the content of nutrients in the soil, which was tested before the commencement of agrotechnical treatments in 2015. The same applies to all years of research. The annual incorporation of plant biomass resulted in a gradual increase in the level of humus in the reclaimed soil . The year 2014 is treated as the starting year in the conducted experiment. In 2015 we did not observe any increase of the organic matter content in the soil and it remained on a very low level of 0,88 %. It was due to the relatively small amount of plant biomass received and plowed in in 2014. Between 2015 and 2016 the increase of the OM was observed as we noted 10 % increase but is was not statistically significant. A statistically significant increase was observed in 2017. The soil survey carried out in 2017 showed a significant increase in the level of humus in the soil also in relation to the initial data from 0,87 % to 2.44 %. In the last year of experiment in 2018 we did not observe the further increase of the OM content but the deviations of the measurements decreased. In this year we did not note the large differences between samles analyzed. It is widely agreed that successful reclamation of lignite mine sites, especially when the topsoil has been removed, depends on the rapid formation of a surface horizon rich in organic matter Humic substances improve the physical properties of mine soils by favouring aggregation, which facilitates aeration and water transport. They also improve the chemical properties of soil by providing buffering capacity and increasing surface area and ion exchange capacity. As a result soils on reclamation sites can become progressively more productive with time . It the case of the presented survey we have observed relatively fast building up of the soil organic matter. Already after four years in the top layer of the studied minesoil the OM reached the level observed in the undisturbed agricultural soils of the region.

It is in line with the other authors reporting that reclaimed minesoils develop recognizable horizonation relatively quickly and effectively sequester carbon . It was reported that a distinct horizon up to 15 cm thick can develop during first 5 years of reclamation and is distinguished from subsoil by the accumulation of SOM, loose soils due to root growth, and soil structure development . The potential of organic matter sequestration in minesoils depends on biomass productivity but also on root development in the subsoil and changes in minesoil resulting of their development . Hemp grown in the optimal soil condition has a well-developed taproot system, growing into the soil to a depth of about 2 m. Duringthe course of the experiment we have observed the changes of hemp root architecture . In the first years the typical tap root was hardly visible. The lateral roots were numerous, but small and thin and outgrown rather the top layer of the minesoil. In later years, the plants began to develop a tap roots, typical for this species, which penetrated well into the soil. The root was still thinner compared to the plants grown on agricultural soils, but the root system looked typical for cannabis. Roots provide a path for movement of carbon and energy to the deeper horizons of the recultivated minesoil. Therefore, cannabis grow lights root production have a direct impact on the amount of organic matter present in the soil . The fine root contributions to SOC range from 33 to 67 percent in forest ecosystems . Balesdent and Balabane calculated that corn roots incorporated 58 percent more carbon than combined incorporation by leaves and stalks. From this perspective, the use of hemp, capable of producing a large amount of above ground biomass and at the same time developing a strong and deeply growing root system, for the rehabilitation of areas poor in organic matter, seems to be justified as deep-rooted plant species have the potential of increasing SOC sequestration by transferring more OM into deeper horizons. In many cases reported in the literature the minesoils formed after lignite mining suffer with low or extremly low pH. It was not observed in our case. During the course of experiment the pH of the minesoil remained alkaline, close to neutral . We have observed slight increase of the soil pH value during the years. Soil pH is one of the main factors determining soil fertility and it may be affected by crop and residue management. Reports on the effect of organic matter addition on soil pH have been contradictory. Some authors have suggested that accumulation of fresh organic matter may be one of the causes of soil acidification while many other reported soil pH increase after OM incorporation .

Our observations are in line with the latter reports. The the exception from this trend was observed in the second year when pH dropped from 7.7 in 2014 to 7.4. This drop was due to the lack of the soil structure typical for the minesoil at the begining of rehabilitation process, resulting with the lack of oxygen in the top layer. These together with the incorporation of the initial amount of the organic matter from the previous year could lead to the anaerobic microbial processes in the soil, production of organic acids and lowering the soil pH. The amount of all four tested macroelements increased during the course of the minesoil reclamation experiment however, the content increase dynamics was different in the case of the analyzed elements . The content of phosphorus and, to some extent, also potassium increased in proportion to the increase in the content of organic matter . At the same time, the magnesium content increased linearly in each year of the experiment, and the changes in the manganese content corresponded to the changes in the soil pH . The content of phosphorus in the tested soil increased with the reclamation carried out. This increase was statistically significant. The level of phosphorus in the reclaimed soil was below the norm, ranging from 101 to 150 mg kg of typical agricultural soil. During first two years it was extremely low . In the third year phosphorus level increased by 39 % and in 2017 by next 42 % reaching 117 mg kg. In the last year of the experiment the phosphorus content did not increase anymore but in the last two years the soil reached the minimal accepted level of 100 mg kg.

Over-expression of WRKY2 in wheat enhanced the tolerance of transgenic wheat to drought stress,while over-expression of WRKY44 and WRKY46 enhanced the tolerance of both drought and salt stress,respectively.In addition,it is reported that WRKYs can also participate in the response of hormone signals.For example,salicylic acid  can activate the expression of WRKY70 transcription factor,while jasmonic acid  inhibits its expression.ABA can induce the WRKY gene to regulate the abscisic acid and gibberellin signaling pathway.Previous studies have proved that WRKY genes can regulate stress,respond to hormone signals to affect plant growth and development,and also plays an important role in fiber development.Gibberellins,as a type of important plant growth regulator,play a key role in fiber development and stem elongation.However,there is no report on the WRKY  gene in seed hemp so far.It is imperative to identify and analyze WRKY transcription factors in seed hemp based on its whole genome and transcriptome data.The aims of this study were to identify CasWRKY genes at the whole genome-scale,analyze its expression patterns in different tissues,and analyze the effect of CasWRKYs on plant height according to GA3 stress in seed hemp.The diversity of gene structure can reflect the evolution of polygenic families.To gain the structural evolution,the exon–intron structures of the CasWRKY genes were determined by comparing the cDNA sequences of WRKYs with their corresponding genomic DNA sequences and then visualized by GSDS  program..Gene structure analysis showed that the number of exons ranged from 2 to 6.More than half number  of the CasWRKY genes had three exons.This indicates that exon loss and gain events occurred in the CasWRKY gene family during evolution,which may be the reason for the functional diversity among CasWRKY genes.

In addition,it was found that CasWRKY genes of the same group had similar exon/intron structures.Members of II-c and II-e had fewer exons and simple structures,while,members of I、II-a and II-b had many exons.To gain insights into the conservation and diversification,marijuana grow system motif structures on 39 CasWRKY proteins were constructed using the MEME program.A total of 10 conserved motifs were identified in the 39 CasWRKY protein sequences.The length of ten identified conserved motifs of CasWRKYs ranged from 6 to 50 amino acids.The number of motifs in CasWRKY proteins ranged from 5 to 15.As expected,most CasWRKYs that have been observed to be in the same group or subgroup usually shared highly similar motif compositions.Among them,motifs 1 and 3 contained the heptapeptide stretch WRKYGQK,with motif 3 being present only in group I.Motifs 1 and 2 were distributed all over the groups and motif 2 was immediately downstream of motif 1.In addition,five genes have similar protein lengths and same motif distributions.Motif 8 was present only in groups II-a and II-b,while Motif 6 was found mainly in subgroup II-B.Motif 4 was present in most genes in groups I and II-c.Furthermore,although CasWRKY27 belonged to subgroup II-d,it had similar conserved motifs with subgroup II-c.Totally,the analysis of CasWRKY motifs showed that every group or subgroup of CasWRKYs had similar motif compositions,which further validated the taxonomic and phylogenetic relationship ofCasWRKY.The cis-acting elements in the promoter region are essential for gene expression.The 2000 bp upstream promoter regions were searched using Plant CARE,and it was found that there are many types of cisacting elements.Among them,twenty cis-acting elements contain hormone-related elements,promoter-related elements,stressrelated elements,development-related elements.the 20P-box  were distributed on the promoter region of 13 CasWRKY genes.The genes that contain P-box were concentrated in group I,group II-b,group II-c,III.Particularly,CasWRKY05 promoters had four gibberellin-responsive elements.In addition,cis-acting regulatory elements involved in light responsiveness were analyzed.17 CasWRKY promoters contain part of a light-responsive elements,which are cis-regulatory elements essential for light induction.It was noted that the three genes  contain the common cisacting elements in promoter and enhancer regions.These results showed that most of CasWRKYs might play a crucial role in multiple stress responses in seed hemp.To investigate the plant in response to hormones at the growth boom in seed hemp,several phenotype responses induced by hormones were studied.

Changes in plant height after treatment with different exogenous hormones were shown in Fig.S.1.After the first exogenous hormone treatment,the plant height changes of different concentrations of GA3 treatments were significantly different.After 5 consecutive treatments,the plant height variation of high concentration  GA3 treatment was significantly higher than that of the other two low concentration GA3 treatments and other exogenous hormones.No significant phenotypic differences were observed after treatment with exogenous hormones IAA and BR compared with the control.These results showed that GA3 at different concentrations could promote the plant height of “Yushema”,while BR and IAA had no significant effect.The above results indicated that “Yushema” was a gibberellin-sensitive variety.Since bio-active GA3 plays the key roles in the development of the stem,the RNA-seq data sampled from different time after GA3 treatment were used to study the differential expression pattern of CasWRKY genes under the GA3 stress.At 24 h of GA3 stress,most genes showed different expression levels and expression patterns,but some genes in the same subfamilies showed the same expression patterns.The expression levels of CasWRKY01,CasWRKY02,CasWRKY06,CasWRKY24,and CasWRKY29 were significantly up-regulated at 3 h after GA3 treatment.Moreover,thirteen genes exhibited the opposite trend with exposure to GA3 stress.In addition,among these 39 CasWRKY genes,the transcription levels of 4 CasWRKY genes s were continuously up-regulated in the stem barks at different time points under the GA3 stress.It should be noted that the expression of CasWRKY09 was significantly down-regulated after GA3 treatment,and then gradually up-regulated.Interestingly,nine  out of the 39 CasWRKY genes were not expressed at all-time points,indicating that they might be pseudogenes or may not be involved in expressed in the stem barks.These results suggest that CasWRKY genes in seed hemp could respond to GA3 stress and form a complicated network to regulate hormone regulatory network.To verify the accuracy of RNA-seq data,9 CasWRKYs were randomly selected for RT-qPCR analysis.The results showed that the RT-qPCR assays of the expression patterns of the 9 CasWRKY genes were similar to the results of FPKM.As one of the largest transcriptional regulatory factor families in plants,WRKY gene family plays important role in plant growth and development and abiotic stress.To date,WRKY genes have been widely studied in a variety of plants,but similar studies have not yet been performed in seed hemp.we identified a total of 39 WRKY genes in the whole genome of seed hemp.The number of WRKY genes in seed hemp is significantly lower than that in A.thaliana ,soybean ,cabbage.hypogaea ,and cotton ,close to that in E.ulmoides ,C.capsularis ,sugar beet ,and canola.

By comparing with different species,it was found that the number of WRKY genes in different species is not directly related to their genome size.Previous studies believe that gene replication,fragment replication,and whole-genome replication play crucial roles in the large-scale expansion of gene families.With the continuous progress of high-throughput sequencing technology and the continuous optimization of data analysis methods,WRKY gene family members have been comprehensively studied.In this study,we conducted a comprehensive genome-wide analysis of WRKY gene family based on the seed hemp genome for the first time.Therefore,the results of this study will contribute to further functional analysis of WRKY genes in seed hemp and provide a reference for gene family analysis of other species.In Arabidopsis,a widely accepted WRKY gene family classification system was established by analyzing the genome data of WRKY gene family.According to the classical classification on the basis of sequence alignment and phylogenetic tree analysis,39 WRKY proteins identified in seed hemp were divided into three main groups,and group II of proteins was further clustering into five subgroups.Among the 39 CasWRKY proteins,there are five proteins in Group III,eight proteins are in Group I,and the remaining 26 CasWRKY proteins belong to group II.This classification results were similar to that in Eucommia ulmoides,Brassica napus  and Brassica rapa,and the maximum numbers of group II proteins in this gene family,which means that this group may have experienced more gene duplications during the process of evolutionary.However,group III has the largest number of WRKY genes in rice,while group I has the largest number in Arabidopsis andpoplar.In this study,three domain loss events were found and concentrated in group III,which is a common phenomenon in the plant WRKY gene family and is considered to be a divergent force for the expansion of this gene family.In addition,it was also found that majority of the CasWRKY genes contain a highly conserved heptapeptide WRKYGQK motif followed by a C2H2 or C2HC type zinc finger motif except for several variants.WRKYGQK,a highly conserved domain,was replaced with WRKYGKK in CasWRKY20 and CasWRKY21.Both genes belong to subgroup II-c.Similar phenomena have been reported in Arabidopsis and cucumber.Previous reports have shown that the WRKYGKK domain failed to bind to W-box,and it needs further verification about whether CasWRKY20 and CasWRKY21 can bind to the W-box.

In addition,previous studies indicated that variations in the WRKYGQK motif of WRKY domain might influence normal interactions of WRKY genes with downstream target genes,cannabis vertical farming and therefore the molecular mechanism of these family members in plants still needs to be further explored.During the process of evolution,tandem and segmental duplication contribute to the expansion of the WRKY gene family.These replicated WRKY genes may form new gene functions to adapt to various conditions required in the process of plant growth and development.Chromosomal distribution and synteny analyses revealed that six  tandem duplication events with 12 CasWRKY genes and five segmental duplication events with 10 CasWRKY genes were observed.The number of tandem duplications was more than segmental duplications,which increased the number of members in the WRKY gene family of seed hemp.Therefore,it could be deduced that tandem and segmental duplication were the main evolutionary driving force of the WRKY gene family in the evolution of seed hemp.In general,analyzing the distribution of introns and exons can help us better to understand the phylogenetic relationship,because they play crucial rolse in the evolution process of many gene families.Here,the comprehensive analysis of the distribution and length of exons and introns of CasWRKY genes were conducted.By analyzing the gene structures of CasWRKYs,it was found that exon loss and gain events occurred in the evolution of CasWRKY gene family,which may increase the functional diversity of genes in the gene family of CasWRKY.Cis-acting elements of promoters are essential for gene transcription and expression.Twenty cis-acting elements involved in hormone-related elements,promoter-related elements,stress-related elements,development-related elements,and cis-acting regulatory elements involved in light responsiveness were analyzed.It should be noted that 20P-box  were distributed on the promoter region of 13 CasWRKY genes,the genes that contain these response elements are concentrated in group I,group II-b,group II-c,group III,and CasWRKY05 promoters had four gibberellin-responsive elements.These results suggest that these genes may produce corresponding expression responses under gibberellin stress,which will be conducive to the functional study of CasWRKYs.It is well known that gene expression pattern is closely related to gene biological function.In the present study,all 39 tested CasWRKY genes were found to be expressed in at least one of those tissues,except that CasWRKY22 and CasWRKY39 were not expressed in the three tissues examined and might be expressed in other tissues.

In addition,some CasWRKY genes showed preferential expression in all tissues tested.For example,six genes have high expression levels in stems and are mainly concentrated in group I.The CasWRKY genes which exhibited preferentially expression among different tissues are likely to have a unique role in organ development.In addition,CasWRKY15 was tissue-specific and is expressed only in stems.Its orthologous gene Atwrky12 in Arabidopsis has been reported to participate in the formation of secondary cell walls which could significantly increase plant biomass.These results suggest that the expression of WRKY transcription factor may be conducive to the regulation of fiber development,at least there is a certain relationship between them.WRKY transcription factors not only play vital roles in plant growth and development but also play key roles in response to various hormone regulations,which provides a favorable guarantee for crop genetic improvement.Phytohormones play an irreplaceable role in plant cellulose biosynthesis.As a key hormone,gibberellin participates in a variety of regulatory processes of plant life activities and almost accompanies entire plant life.Gibberellin can greatly affect fiber initiation,differentiation,and development,and promote fiber elongation by inducing more fiber initial cells.In this study,spraying gibberellin on plants of “Yushema” significantly promoted the elongation of plant heights,which proved that “Yushema” was the typical gibberellinsensitive germplasm.Therefore,the expression patterns of 39 CasWRKYs under GA3 stress were systematically analyzed.Expression pattern showed that most genes showed different expression levels at 24 h of GA3 stress,but some genes in the same subfamilies showed the same expression patterns.

Hemp’s central woody portion contains 36% cellulose and 27% lignin,whereas bast fiber contains 72% cellulose and 4% lignin.The whole hemp stem contains 47% cellulose and 18% lignin,which is more favorable than pine and birch wood.Hemp stalk contains the highest percentage of cellulose,with the lowest lignin content over almost all non-woody stalks.However,hemp bast fiber secures second for alpha-cellulose after cotton.The lignin and cellulose content in hemp stalks considerably vary among cultivars and growing seasons.The morphology and low lignin content of hemp bast fiber allow easy penetration of processing chemicals resulting faster pulping process with less harsh chemical use.Hemicellulose enhances swelling of the pulp and bonding capacity among the fibers and provides the necessary strength to paper.The hemp core has a higher ability to supply alpha-cellulose to fibrous suspensions and a similar amount of hemicellulose than that of kenaf and hardwood.Hemp fiber exhibited high yield and high tear strength of paper obtained by organosolv pulping process due to having long fibers in pulp.It allows a safer oxygen delignification process with a higher yield than that of birch or pine pulps.The organosolv pulping uses organic solvents to solubilize lignin and hemicellulose,which avoids environmentally harmful sulfur used in conventional pulping techniques,offers high-quality lignin recovery,and easy removal of solvents with less water consumption compared to kraft pulping process.The organosolv process,trim tray for weed which utilizes ethanolamine,produces high quality hemp core pulp.

Moreover,hemp paper processing does not require harmful chlorine bleach; instead,it can use peroxide,which is safer for the environment.In searching for a sustainable pulping process from non-wood feedstock,BioRegional MiniMill technology has been claimed as a promising zero-emission environmentally friendly process for small-scale production.Alkaline pulping of woody hemp core enhances fibrillation and forms inter-fiber bonding which imparts strength in paper and can produce smooth printing grade paper as produced from straw and hardwood pulp.A combination of hemp hurd pulp with hardwood exhibited improved tensile index,bursting strength,softness with identical water absorbency of hand tissue.Blending hemp fiber or woody core with pine and eucalyptus demonstrates higher fiber length in pulp,hence the sufficient paper strength.In most cases,only hemp bast fibers are used for paper-making purposes because of outstanding tearing strength,although lower tensile strength.The successful use of hemp as paper-making materialdepends on the technical viability of exploitation of both fiber and woody core,not simply one since their differences in morphology and chemical compositions offer suitability for paper-making raw materials.The bleached kraft pulps from hemp stalk were found useful raw material than hemp bast fiber or woody core alone .Organosolv pulping process of whole hemp stalks exhibited the strength between commercial hardwood and softwood pulps.Hemp with core and sheath showed a slightly higher kappa number  than eucalyptus,indicating that it is more difficult to delignify in kraft cooking process due to lower degree of core fiber polymerization.Strengths are affected due to low hemicellulose content and a lower degree of internal fibrillation.Hemicellulose helps the pulp sheet by strengthening its tensile,bursting,tear strength,specific surface,folding endurance and opacity.The elementary chlorine-free bleaching method with enzyme treatment is not suitable for hemp stalks since it deteriorates the physical properties.It was suggested that separate pulping of fibers and cores followed by blending could yield a pulp with desired properties for multipurpose applications.

Unlike wood paper,hemp papers survive hundreds of years and do not get into decomposition and yellowing due to aging.Hemp paper’s high tear strength and wet strength make it ideal for currency paper,art paper,cigarette paper,tea bags,specialty non-wovens,carbon tissue,grease-proof paper,and other applications.The paper made from hurds can also be used as low-grade printing paper without compromising the quality of the printing surface.Hemp paper showed better oil/air filtration performance than cotton paper in practical application.As a non-wood fiber,hemp also has considerable shortcomings for industrial-scale paper making.Existing paper-making technology is not well capable of handling non-woody crops,and it significantly decreases productivity.In most cases,fibers are separated from the woody core and go through the process separately.The processing technology of hemp woody core and even the separation method of bast fibers must be introduced with state-of-the-art knowledge to reduce costings.Technological advancement is also required to process the whole stalk without separation of fibers and woody core for achieving more yield.Since hemp is an annual crop,and its stalks are very bulky,some difficulties are associated with transportation,storage capacity,and smooth handles.Long-time storage can damage the fibers and cause color change.Pulp quality and yield is related to morphology and chemical composition; they can be affected by harvesting time,geographic location,plant breeding,and even the variation are observed within the biomass,which may lead to a possible lack of consistency to paper quality.The globally produced agricultural residue could produce five times more paper than demand,but technology fails to exploit those in the paper industry.According to the study on different pulping methods of hemp bast fiber,it is found quite acceptable in place of wood from the technical point of view,and even woody cores can also be a promising raw material for paper.Hemp pulps are generally used by mixing with wood pulp,and currently,100% hemp paper production is not seen.Hemp is speculated to take the opportunity to outvie the other non-wood plants by its yield and grow ability in moderate or boreal climates.Easy pulping,good quality bleached paper and specialty papers are the key advantages of hemp.Hemp,the second largest grown bast fiber after jute,has gained considerable attention as a reinforcement in the polymer matrices in the last decade due to its renewable,biodegradable,and recycling properties.

Several composite processing methods have been investigated,including hand lay-up,film stacking,vacuum infusion,manual winding,filament winding,resin transfer molding,pultrusion and injection molding,to name a few.Hemp fiber composites with thermoset,thermoplastic and biodegradable matrices have demonstrated strong mechanical properties due to higher tensile strength of fiber up to 1110 MPa.Table 2 summarizes some important physical and mechanical properties of vegetable-based natural fibers.Thermoplastic matrix composites perform better over thermoset matrix composites concerning high specific strength,corrosion resistance,cost efficiency,recyclability and design versatility.But the main drawback of natural fiber-reinforced thermoplastic composite is that their processing temperature needs to be kept below 230 C to protect them from thermal degradation .Hemp fiber begins to degrade at a temperature above 150  C,hemicellulose and pectin decompose at around 260 C,while cellulose decomposes at about 360  C .Hemp fiber-reinforced thermoplastic composites are typically made of polyethylene,polyurethane,or polypropylene matrices.It shows the potential to replace synthetic fiber composites in many lightweight and low-cost applications .The frequently used thermoset matrices for hemp fiber-reinforced composites are epoxy resin,phenolic,vinyl ester,or unsaturated polyester resin.Composites made from hemp fiber with thermoset matrices are creep resistant,solvent resistant,and tough.W€ otzel et al.investigated a life cycle study on materials reinforced with hemp fiber against ABS  for car parts.Their study revealed that cumulative energy demand for producing hemp composite was half compared to the ABS basic component and hemp composite for an inner lining of cars showed more ecological benefits.Green composites are referred as bio-composites,the combination of natural fibers with biodegradable polymeric materials.Researchers focused on green composite due to dwindling fossil fuel resources and their negative impacts on environment.The biodegradable polymer matrices such as epoxidized soy oil ,acrylated epoxidized soybean oil,starch-based emulsion,cashew nutshell,euphorbia oil,cellulose acetate and polylactic acid were used to develop hemp fiber-reinforced green composites in number of studies and outstanding mechanical properties for primary structural applications were observed.Though cost and service longevity due to decomposition in nature are associated as drawbacks with green composites further study may open new door to overcoming these barriers.

Mechanical properties of fiber-reinforced composites strongly depend on fiber length,diameter,orientation,degree of dispersion,aggregate formation and fiber-matrix compatibility.Hemp is susceptible to thermal and oxidative degradation during processing.Another key impediment to manufacturing hemp-reinforced composites is the inability of hydrophilic lignocellulose fibers to adhere to hydrophobic matrices.Due to their polar surface character,natural fiber reinforcement shows lower compatibility with strongly apolar thermoplastic matrices.Again,vapor and void creation during processing due to moisture content,photodegradation due to UV radiation,and poor resistance to moisture can significantly affect the performance of the composite for outdoor application.A summary of the performance of hemp composite against moisture can be seen in Table 3.Hemp composites absorb moisture,and when dry,the constituent fibers shrink rapidly.Thus interfacial bonding of composites no longer can retain due to cyclic absorption and desorption of moisture and eventually debonding cracks occur inside the structure which allows room for further water penetration.The schematic diagram of the mechanism is illustrated in Figure 2.Alongside the formation of cracks,moisture uptake also encourages colonial fungal growth that further accelerates the degradation of the composite.Several researchers studied the relationship between fiber fraction and amount of moisture absorption and concluded that for natural fiber,moisture absorption increases with increasing fiber loading.For solving these inherent limitations,many studies were carried out on physical and chemical modification of natural fibers to enhance surface characteristics and effectiveness as a reinforcement material.Coupling agents were used in some experiments in chemical modification and better compatibility was achieved between cellulose fibers and hydrophobic polymers.Treating hemp fibers with methacrylic anhydride increases interfacial adhesion between hemp and polyester matrices.Mwaikambo and Ansell found that hemp fibers with a 4% & 6% alkalized treatment had the highest modulus and tensile strength.Propionylation and acetylation treatments on hemp fibers resulted in a reduced hydrophilicity but at the same time,decreased crystallinity slightly.The Scanning electron microscope  results  showed that the esterified materials’ surfaces were smoother than the untreated hemp fibers.Dayo et al.studied the influence of different chemical treatments on hemp composite and recorded the lowest water absorption for silane treated fiber.The same author also reported a similar result from another experiment where only washed,trimming tray weed alkaline treated and silane treated hemp fibers were compared.

Among the resins,Polybenzoxazine polymers showed better resistance against moisture absorption with additional advantages like good mechanical and thermal properties.Oza and Lu investigated the effects of silane and NaOH treatment on the thermal and thermomechanical properties of hemp fiber-reinforced high-density polyethylene composites.They observed that thermal stability decreases as fiber loading increases,and treated fiber composites show higher thermal stability than untreated fiber composites.The storage modulus of treated composites was higher than that of untreated composites in dynamic mechanical analysis.Up to 40% fiber loading,the storage modulus value increased,while it dramatically decreased at 50% fiber loading.It was found that the storage modulus of Silane-treated composites was higher than NaOH-treated fiber composites.A similar achievement was also reported by Dayo et al..A summary of hemp composites’ mechanical,thermal and thermomechanical performance can be seen in Tables 4 and,respectively.Hemp fibers have significant advantages over synthetic fibers in reinforcing composites and can be used efficiently for a variety of applications because of their high specific strength,low density,low production cost,bio-renewable nature and eco-friendly behavior.The applications of hemp-reinforced composites had been traced in the automotive industry in the 1940s,where Henry Ford produced car components from hemp fiber with soybeans-based bio-matrices.It is predominantly used in the automotive sector to reinforce door panels,passenger rear decks,pillars,and boot linings .Compared to other natural fibers,its uses have remarkably increased in the German and Austrian automotive industries.Due to the higher vibration damping capacity of hemp fibers,researchers also focused on hemp composites in manufacturing sporting goods and musical instruments.Claudio and Marco developed electronic racks for the helicopter by utilizing hemp fabric/epoxy composite materials.The study revealed that this electronic rack from hemp composite was 55.6% lighter than existing steel electronic racks.Hemp fiber reinforced with polycaprolactone composites proved their potential application in fabricating orthotic devices .Hemp chair was developed from hemp yarns with epoxy resin,and Xia et al.innovated a hybrid composite from hemp fiber mats and aluminum sheet with epoxy resin which offered excellent electromagnetic interference  shielding performances.The term “plastic” refers to a material’s flflexibility or ability to deform into any shape without breaking.Plastic is a carbon chained polymer allowing it to be molded into any shape; that is why they are the most adaptable material.The majority of monomers used to make plastics like ethylene and polypropylene are derived from fossil fuel hydrocarbon.As a result,they are neither biodegradable nor easily decomposable; instead,they accumulate in the landfill and the natural environment.According to literature,roughly 9% of all plastics produced are recyclable,while the remaining 79% end up in landfills and the atmosphere.Petroleum-based plastics and its by-product have a devastating effect on the land,water,and wildlife.For this reason,increasing demand has been started in the world for the usage of high-performance bio-based plastics capable of being environmentally friendly and compensating depleting of petroleum resources.Hemp plastic which is 100% biodegradable,can be a better alternative to synthetic plastic.The cellulose of the hemp plant is rated 60–70%,which can be extracted for making a different range of plastics,including rayon,celluloid and cellophane.