Date Palm Leaf Research Articles

Dual-strategy approach for Rhynchophorus ferrugineus control: Endophytic Beauveria bassiana and Bacillus thuringiensis topical application

In an innovative approach to biological pest management, the entomopathogenic efficacy of endophytically colonized Beauveria bassiana and topically applied Bacillus thuringiensis was evaluated against various larval instars (2nd, 4th, and 6th) of the red palm weevil (RPW), Rhynchophorus ferrugineus. Initially, date palm leaf petioles were inoculated with five distinct isolates of the fungus to ascertain their endophytic potential over two years. Subsequently, the most proficiently colonized fungal isolate was selected for subsequent experimentation. During individual entomopathogen applications, larval instars of RPW were presented with plant petioles and colonized with fungus at 30 days post-inoculation or immersed in bacterial inoculum. Ιn combined treatments, larvae were exposed to both entomopathogen-treated plant petioles concurrently. The tested bacterium was administered at three concentrations (30, 40, and 50 μg/ml). Larval mortalities were markedly lower in treatments involving individual entomopathogens, whereas integrated applications yielded higher mortalities. Treatments associated with heightened larval mortalities corresponded to diminished pupation, adult emergence, and egg eclosion rates. Furthermore, the simultaneous application of both entomopathogens bolstered larval mortalities of RPW both additively and synergistically, with concentration also playing an important role. Similarly, the developmental periods of various insect stages were substantially influenced by combined entomopathogen applications. The inherent prevalence of these pathogens and their ability to colonize crop plants internally for extended periods render them promising agents against cryptic-feeding insects like RPW. However, further evaluation of suitable entomopathogen strains and optimal doses under field conditions is imperative before formulating concrete recommendations for date palm growers.

Natural fibers for performance boosting of BaTiO3-PDMS flexible piezoelectric composite generators

Among biobased materials, date palm leaf fiber (DPLF) is a cellulose-rich fiber with considerable potential for use in sustainable composites, where it can improve mechanical properties and reduce weight. In this study, a flexible piezoelectric generator (PEG) composed of a polydimethylsiloxane (PDMS) polymer, lead-free barium titanate (BaTiO3), and DPLF are presented. A comparative analysis assessed the impact of incorporating DPLF through morphological, mechanical, and electrical evaluations. The results indicate that DPLF improves the performance of the PEG while maintaining desirable mechanical properties, such as flexibility and durability. The improved performance can be attributed to the enhanced dielectric properties, robustness, and distribution of the piezoceramic particles. PEG (5 wt% DPLF + 15 wt% BaTiO3) exhibits a maximum open-circuit voltage twice that of 15 wt% BaTiO3 PEG (6 V) and an eightfold higher power density (8 μW/cm2). These findings result from an increased dielectric constant of 6.8 and a favorable capacitance of 30 pF. Incorporating cellulose-rich DPLF significantly impacts the electromechanical performance of the PDMS/BaTiO3-DPLF composite due to several beneficial effects, including good particle dispersion, sustainability, improved homogeneity, and improved dielectric properties.

Dyeing of Cotton Woven Fabric Using Sustainable Natural Dye (Date Leaves) and Bio-Mordants

This study on natural dyes has been chosen for a sustainable dyeing method on textile through the using of 99% cotton 1% spandex woven fabric. The dye was produced from the Date Palm Leaf (Phoenix dactylifera L) using Soxhlet machine through continuous extraction method and dyed using natural bio-mordant eucalyptus, guava leaf. Fourier transform infrared spectroscopy (FTIR) test was carried for nanoparticle characterization along with color measurements with specular and UV include mode. The dyed fabrics were also assessed for wash fastness, fastness against perspiration, dry rubbing and wet rubbing property. In most of the cases the fastness property of sample without mordant is better than with mordant. Cotton fabric is used for dyeing to make it sustainable and to reduce the dependency on synthetic dyes; the natural material can also reduce the pressure on synthetic material.

Impacts of aquaculture wastewater irrigation on soil health, nutrient availability, and date palm fruit quality

Water scarcity and droughts are among the most challenging issues worldwide, particularly in arid and semi-arid regions like Saudi Arabia. Date palm (Phoenix dactylifera L.), a major crop in Saudi Arabia, is being significantly affected by water scarcity, soil salinity, and desertification. Alternative water sources are needed to conserve freshwater resources and increase date palm production in Saudi Arabia. On the other hand, Saudi Arabia has a significant number of aquaculture farms that generate substantial amounts of wastewater, which can be utilized as an alternative source of irrigation. Therefore, this study aimed to assess the potential of aquaculture wastewater as an alternative irrigation source for date palm orchards. Aquaculture wastewater was collected from 12 different farms (Al-Kharj, Al-Muzahmiya, and Al-Qassim regions, Saudi Arabia) and its quality was analyzed. The impacts of aquaculture wastewater irrigation on soil quality, nutrient availability, nutrient status of date palm trees, and dates fruit quality were assessed in comparison to source water (freshwater) irrigation at Al-Kharj, Al-Muzahmiya, and Al-Qassim regions. The water quality analyses showed higher salinity (EC = 3.31 dSm−1) in farm Q3, while all other farms demonstrated no salinity, sodicity, or alkalinity hazards. Moreover, the aquaculture wastewater irrigation increased soil available P, K, NO3−–N, and NH4+–N by 49.31%, 21.11%, 33.62%, and 52.31%, respectively, compared to source water irrigation. On average, date palm fruit weight, length, and moisture contents increased by 26%, 23%, and 43% under aquaculture wastewater irrigation compared to source water irrigation. Further, P, K, Fe, Cu, and Zn contents in date palm leaf were increased by 19.35%, 34.17%, 37.36%, 38.24%, and 45.29%, respectively, under aquaculture wastewater irrigation compared to source water irrigation. Overall, aquaculture wastewater irrigation significantly enhanced date palm plant growth, date palm fruit quality, and soil available nutrients compared to freshwater irrigation. It was concluded that aquaculture wastewater can be used as an effective irrigation source for date palm farms as it enhances soil nutrient availability, date palm growth, and date fruit yield and quality. The findings of this study suggest that aquaculture wastewater could be a viable alternative for conserving freshwater resources and increase date palm production in Saudi Arabia.

Utilizing Date Palm Leaf Biochar for Simultaneous Adsorption of Pb(II) and Iodine from Aqueous Solutions

This study addresses the environmental and health hazards posed by Pb(II) and iodine, two significant contaminants. The objective was to explore the adsorption of these substances from aqueous solutions using biochar derived from the leaf midribs of the date palm through a slow pyrolysis process. The pyrolysis was conducted in two stages within a vacuum furnace: initially at 300 °C for 1 h followed by overnight cooling, and then at 600 °C with a similar cooling process. The resulting biochar was characterized for its microstructural features and functional groups using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. It exhibited a porous structure with large numbers of pores (20 to 50 μm in size) and functional groups including O-H, C-H, and C=C, which are integral to its adsorption capabilities. For the adsorption studies, a 100 ppm Pb(II) ion solution was treated with varying amounts of biochar (20, 40, 60, and 80 mg) for 24 h. In parallel, iodine adsorption was tested, with biochar quantities ranging from 0.1 to 0.4 g/50 mL. Both treatments were followed by filtration and analysis using atomic absorption spectroscopy to determine the remaining concentrations of Pb(II) and iodine. The study also explored the effect of varying incubation periods (up to 30 h) on iodine adsorption. The results were significant; 100% adsorption of Pb(II) was achieved with the addition of 60 mg of biochar per 10 mL of solution. In contrast, for iodine, a maximum adsorption of 39.7% was observed with 30 mg or 40 mg of biochar per 50 mL. These findings demonstrate the potential of date palm-derived biochar as an effective and sustainable material for the removal of Pb(II) and iodine from contaminated water, offering valuable insights for environmental remediation strategies.

Biochar from Date Palm Waste via Two-Step Pyrolysis: A Modified Approach for Cu (II) Removal from Aqueous Solutions

Heavy metals such as copper, often discharged from industrial processes and agricultural activities, pose significant environmental and health risks due to their toxicity, particularly in the soluble form of Cu (II). This study investigates the effectiveness of biochar produced from date palm leaf midrib waste via a two-step pyrolysis process, as a sustainable and economical adsorbent for removing Cu (II) from aqueous solutions The biochar was characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis. Adsorption experiments were conducted to evaluate the effects of pH, adsorbent dosage, contact time, and initial Cu (II) concentration. The maximum adsorption capacity was observed at pH 6, with a capacity of 70 mg/g. The adsorption data were best described by the pseudo-second-order kinetic model, indicating chemisorption as the primary mechanism. Thermodynamic studies indicated that the adsorption process was spontaneous and exothermic, with a Gibbs free energy change (ΔG) of −1.245 kJ/mol at 25 °C, enthalpy change (ΔH) of −15.71 kJ/mol, and entropy change (ΔS) of 48.36 J/mol·K. Reusability tests demonstrated that the biochar retained over 85% of its initial adsorption capacity after five cycles, with capacities of 60 mg/g in the first cycle, decreasing to 52 mg/g by the fifth cycle. This study highlights the potential of biochar derived from date palm waste as an efficient, sustainable adsorbent for the removal of Cu (II) from wastewater, contributing to both environmental management and waste valorization. Future research should focus on optimizing the biochar production process and exploring its application for the removal of other contaminants.

Anticancer Properties of Different Varieties of Date Palm (Phoenix dactylifera L.) Leaf Extracts in Human Tumor Cells: a Comparative Study.

Plant polyphenols are nutraceutical components with relevant biological effects on human health. They act against development of several diseases including cancer. In this study, the methanolic extracts of four date palm Phoenix dactylifera leaves (Deglet Noor (DN), Barhee (B), Khalas (KS) and Khunezi (KZ)) collected from south Tunisia were preliminary analyzed for their effects against U87 (human glioblastoma) and MDA-MB-231 (human breast cancer) cell line development. Results showed that Barhee extract (30μg/mL) was the most efficient to reduce the growth of both tumor cells to about 40% (p < 0.05) without inducing cytotoxicity. Significantly, KS, KZ, DN and B extracts (30μg/mL) decreased MDA-MB-231 and U87 cell adhesion towards fibrinogen and fibronectin. Using integrin blocking antibodies, leaf extracts competitively decreased human glioblastoma cell attachment to immobilized antibodies by interfering to αvβ3 and α5β1 integrin receptors. At the same concentration, extracts decreased MDA-MB-23 and U87 cell migration performed with wound healing assay. Particularly, Barhee and Deglet Noor leaf extracts (30μg/mL) significantly reduced U87 cell invasion by 52.92% (p < 0.01) and 74.56% (p < 0.01), respectively. Collegially, our findings revealed beneficial proprieties of four varieties of date palm leaf especially those displayed by DN and B extracts that may serve as active candidates against human glioblastoma and breast cancer progression.

The Utilization of Date Palm (Phoenix dactylifera) Leaf Fiber as a Main Component in Making an Improvised Water Filter

Access to clean and safe water is known to be an obstacle for many people globally, leading to the necessity of creating a water filtration method that is feasible and can be made even in rural and developing areas. This study aimed to make an Improvised Water Filter that is sustainable, cost-effective, and locally sourced, using Date Palm (Phoenix dactylifera) leaf fiber as a main component. The Date Palm leaf fibers were extracted by boiling, drying, and manual scraping. The study strived to investigate the capability of Date Palm leaf fibers alone to improve water quality by testing fungal presence through culturing, physical pollutants by utilizing a microscope, and pH level and salinity levels using a calibrated multitester. The research findings proved the effectiveness of the Improvised Water Filter specifically by reducing fungal colonies by 4.33 and 8.33 in saltwater and contaminated water respectively, eliminating the majority of the physical pollutants by 53.5 micrometers and by 256.3 micrometers, neutralizing the water pH levels by 0.60 and by 0.78, neutralizing the salinity levels by 149.67 ppm and by 338.33 ppm, and exhibiting reliable durability and functionality properties in terms of its structure and filtering media condition with a water flow rate of 1.1L/min and 1.02L/min, and a minimal reduction in the weight of the filtering media by 3.7g and by 3.3g in saltwater and contaminated water respectively. The Improvised Water Filter has effectively filtered and neutralized the water samples, improving the water quality. Future researchers are recommended to conduct comparative studies involving Date Palm (Phoenix dactylifera) and other natural materials, examining filtration capabilities and efficiency, material durability, and by further investigating other water quality indicators to create an improved product that can produce potable and safer water.

Novel Fungal Pathogens Associated with Date Palm Leaf Spot in Egypt

Novel Fungal Pathogens Associated with Date Palm Leaf Spot in Egypt

Water absorption and mechanical behaviour of green fibres and particles acting as reinforced hybrid composite materials

Abstract This paper highlights the results of an experimental study on the preparation and characterization of Luffa cylindrica fiber (LCF) and groundnut shell particle (GSP) reinforced phenol-formaldehyde (PF) hybrid composites. The amount of LCFs was fixed at 25 wt%, while the amount of groundnut shell particles ranged from 0 to 25 wt%. Observations were made regarding the water absorption and thickness swelling behaviour of prepared hybrid composites. In addition, the mechanical behaviours of hybrid composites have been studied under both dry and wet conditions. In comparison to dry conditions, the mechanical properties of the hybrid composites were lower when they were wet. Hybrid composites comprising 25% Luffa cylindica fibre and 15% groundnut shell particle (25LCF/15GSP) exhibit the highest level of mechanical properties under both conditions. The percentages of water absorption and thickness swelling increase as groundnut shell particles increase. The composite 25LCF/25GSP exhibited the highest percentage of water absorption and thickness swelling. Compared to date palm leaf (DPL)-reinforced composites, 25LCF/15GSP showed more significant mechanical and physical properties. We concluded that the inclusion of groundnut shell particles in LCF/PF composites substantially improved the mechanical properties of the hybrid composite. The range of increment, however, was narrower under moist conditions compared to dry conditions.

Laser speckle-based estimation of surface condition for designing quieter material

Laser speckle is a non-contact, non-interfering, non-destructive, rapid and controllable technique with a large area of coverage that has attracted much attention for surface analysis of materials. The emergence of different natural cellulosic materials as potential candidates for the replacement of synthetic ones is promising, but their sustainability from the point of view of material design is still in question. Machining of the surface of cellulosic components for making sound-dampening materials has a critical effect on determining their surface condition. Laser speckle is an emerging tool for surface analysis of a variety of materials, and it has important applications in material design and analysis. As a cutting-edge research tool, ultrasonic wave technology has maintained a significant contribution to the design and structural monitoring of composite materials. The present work uses date palm leaf fibers for composite reinforcement. The sound-dampening properties, such as sound absorption and transmission, were analyzed on the basis of surface roughness observed with the laser speckle technique and modified by ultrasonically blended surfactants. The surface roughness of the synthesized material was found to increase with sonication time with an R 2 value of 0.944 and observed fluctuation in roughness data on the surface of the material. The sound absorption coefficient is 0.98 with a transmission loss of 60 dB, for which the material is classified as an ASTM E1050 Class A acoustic material. Further, the method of laser speckle-based roughness estimation is found to be potential tool for the design of any type of quieter material.

Adsorption of Pb2+ by Activated Carbon Produced by Microwave-Assisted K2CO3 Activation of Date Palm Leaf Sheath Fibres

Date palm trees generate large amounts of various types of waste, including leaf sheath fibres, which can be used as a low-cost precursor for the production of biochar, including activated carbon (AC), which can be employed for the adsorption of contaminants. In the current study, activated carbon was produced from leaf sheath fibres of date palms (LSDPFAC) by the use of chemical activation with K2CO3 combined with microwave irradiation, and it was characterised and evaluated for its adsorptive capacity of lead ions (Pb2+). The Brunauer–Emmett–Teller (BET) surface area, Langmuir surface area, total pore volume and average pore diameter of the LSDPFAC were 560.20 m2/g, 744.31 m2/g, 0.29 cm3/g and 2.47 nm, respectively. A greater adsorption of Pb2+ was observed when its concentration was higher in the solution, and the greatest adsorption capacity of 5.67 mg Pb/g was observed at the highest pH. The results of isotherm and kinetic studies demonstrated that the adsorption of Pb2+ onto the LSDPFAC was best described by the Freundlich isotherm and pseudo-second-order (PSO) models. The Langmuir ΔG° and Ea were 6.39 kJ/mol, 0.12 kJ/mol K, −31.28 kJ/mol and 15.90 kJ/mol, respectively, which demonstrated that the adsorption of Pb2+ by the LSDPFAC was endothermic, spontaneous and governed by physisorption.

Application of natural and modified additives in yogurt formulation: types, production, and rheological and nutraceutical benefits.

Yogurt, a popular fermented dairy product, is of different types and known for its nutritional and nutraceutical benefits. However, incorporating additives into yogurt has been adopted to improve its functionality and nutraceutical properties. Additives incorporated in yogurt may be natural or modified. The incorporation of diverse natural additives in yogurt formulation, such as moringa, date palm, grape seeds and argel leaf extracts, cornelian cherry paste, mulberry fruit and leaf powder, lentil flour, different types of fibers, lemongrass and spearmint essential oils, and honey, has been reported. Similarly, modified additives, such as β-glucan, pectin, inulin, sodium alginate, and gelatin, are also added to enhance the physicochemical, textural, sensory, and rheological properties of yogurt. Although additives are traditionally added for their technological impact on the yogurt, studies have shown that they influence the nutritional and nutraceutical properties of yogurt, when added. Hence, yogurts enriched with functional additives, especially natural additives, have been reported to possess an improved nutritional quality and impart several health benefits to consumers. These benefits include reducing the risk of cardiovascular disease, cancer, osteoporosis, oxidative stress, and hyperglycemia. This current review highlights the common types of yogurt, the production process, and the rheological and nutraceutical benefits of incorporating natural and modified additives into yogurt.

Role of manganese in curing of date palm leaf brittle disease in El-Kharga Oasis, Egypt

Role of manganese in curing of date palm leaf brittle disease in El-Kharga Oasis, Egypt

Engineering Performance of Cement Mortar Cubes Containing Percentage of Date Palm Fibers and Leaf Ash

The problem of conventional cement mortar cubes is the requirement of cement to be used for their production. It is recognized that cement production involves a significant release of carbon dioxide to the atmosphere, which is detrimental to the quality of the environment. To adopt a sustainable development of building materials, date palm tree has been used by numerous researchers to partially replace the cement in the production of mortar cubes. The study aims: 1. To optimize the engineering properties of cement mortar cubes enhanced with date palm fibers and leaves ash. 2. To investigate the microstructures and chemical characteristics of the optimized cement mortar enhanced with waste date palm fibers and leaves ash. The design optimization in this study, mortar cubes were formulated in such a way that the trial mix designs were varied with date palm leaves ash (1% to 10% date palm leaves ash as partial substitute of cement) and date palm, fibers (1% to 5% as partial substitute of silica sand). The mechanism of reaction at early- and long characterization tests studied term period of curing on paste, including water absorption test, Ultrasonic Pulse Velocity (UPV) test, compression test, SEM test, energy dispersive X-ray (EDX) test, X-ray and Fluorescence tests (XRF). As the study's major finding, it was realized that the optimal mix ratio of the treated mortar cubes was noticed to have 4% date palm leaves ash as partial cement substitute and 2% date palm fibers as partial silica sand substitute. There was significant improvement in the treated mortar cubes' engineering properties compared to those of the control mortar cubes. The study outcomes proved that both date palm leaves ash and fibers can cause pozzolanic activity and reinforcing effect on the treated mortar cubes.

Soluble Elements Released from Organic Wastes to Increase Available Nutrients for Soil and Crops

Member States of the European Union must ban burning arable stubble by 2023 and improve the recycling of organic waste into fertilizers and organic farming practices by 2030. The current lack of nutrients from soils and crops leads to food insecurity, human malnutrition and diseases. Consequently, innovative solutions are required, as technosols are constructed by waste. The objective of this paper is to educate on the nutrients that some pruning residues can provide. This work characterizes elemental composition, nutrients soluble fraction and physical and chemical properties of the following organic wastes: almond tree pruning, commercial peat substrate, olive tree pruning, pine needle, date palm leaf pruning, sewage sludge compost and vine pruning. The results show significant differences between macro (Na, K, Ca, Mg) and micronutrient (Fe, Mn, Cu, Zn) content and their solubility. Sewage sludge compost, olive pruning and pine needle are the three residues with the highest presence of nutrients in their elemental composition. Nevertheless, if a farmer applies pruning residues as a nutritional supplement for crops, it will be key to finding the short-term soluble nutrient rate and synchronizing the nutritional requirement curve of a plant’s life cycle with its nutrient release. Consequently, organic waste (without composting treatment) obtains higher solubility rates, being date palm leaf residue the one with the greatest value. The solubility index of organic wastes can be significant in providing short-term nutrients to crops. Hence, our results can help in choosing the proper waste to enhance plant nutrient supply, mainly K, Ca, Mg and Na for crop nutrition, to ensure efficient biofertilization.

Optimizing date palm leaf and pistachio shell biochar properties for antibiotic adsorption by varying pyrolysis temperature

This study implemented biochars produced from two arid agricultural byproducts, date palm leaves and pistachio shells, at pyrolysis temperatures from 400 to 800 °C to remove trimethoprim, sulfamethoxazole and sulfapyridine antibiotics from mixed solutions. By altering pyrolysis temperature and feedstock, produced biochars yielded a range of physicochemical properties resulting in distinct antibiotic adsorption. Antibiotic adsorption capacity generally decreased with increasing pyrolysis temperature, while adsorption affinities were temperature independent for trimethoprim and increased with pyrolysis temperature for sulfamethoxazole and sulfapyridine. Correlation against biochar properties suggested cation exchange capacity and functional group composition related well to adsorption capacity and polarity/hydrophobicity was linked to adsorption affinities. Antibiotic removal efficiencies by biochars from both feedstocks compared favorably against previous reports, with up to 97.6, 98.1 and 99.5 % of trimethoprim, sulfamethoxazole and sulfapyridine removed, respectively. This work relates biochar production conditions to properties and subsequent antibiotic adsorption, demonstrating application of these materials for removing antibiotics from wastewater.

Phenol contaminated municipal wastewater treatment using date palm frond biochar: Optimization using response surface methodology

Phenol is classified as an emerging contaminant which can be very toxic even at low concentrations and should be removed from wastewaters before reaching the environment. In this study date palm frond and leaf were pyrolyzed at different temperatures to identify the best adsorbent (feedstock) and pyrolysis temperature to remove phenol from aqueous solutions. Date palm frond pyrolyzed at 600 °C, termed DPF600, achieved the highest phenol removal rates of 64% and adsorption capacity of 15.93 mg/g. Response surface methodology approach using Box-Behnken design was implemented to obtain the optimal pH (6), contact time (20 h) and dosage (0.1 g) for the maximum phenol adsorption. A predicted adsorption capacity was found as 16.62 mg/g which was in close agreement with the experimental adsorption capacity of 17.38 mg/g. Isotherm and kinetic models in both linear and non-linear forms indicated that Freundlich model (R2 = 0.99, χ2 = 0.02, RMSE = 1.09) and pseudo-second order model (R2 = 0.99, χ2 = 0.85, RMSE = 5.41) fit best the obtained experimental data. Thermodynamics calculations affirmed that the adsorption of phenol onto DPF600 biochar was endothermic and spontaneous. The point of zero charge was found to be at 6.5 for DPF600 biochar. Scanning electron microscopy coupled with energy dispersive X-ray, Fourier transform infrared spectroscopy and X-ray diffraction confirmed adsorption of phenol onto DPF600 biochar. Application of DPF600 biochar to remove phenol from synthetic primary and secondary treated wastewater samples achieved 60 and 85% removal rates and 241 mg/g and 22.28 mg/g adsorption capacities, respectively. Regeneration studies showed promising adsorption capacities indicating the efficacy of DPF600 for the removal of phenol from wastewater.

Variations in composition and stability of biochars derived from different feedstock types at varying pyrolysis temperature

Feedstock type and pyrolysis temperature primarily affect the properties of resultant biochar. Therefore, the effects of several different feedstock types and various pyrolysis temperatures on structural, chemical, proximate, morphological, and elemental compositional characteristics of the resultant biochars were explored. Nine types of wastes (date palm fiber waste (DF), date palm leaf waste (DL), date palm petiole waste (DP), tomato plant waste (TM), cucumber plant waste (CC), poultry litter (PL), chicken feather waste (CH), cow dung (CD), and conocarpus waste (CN) were collected and pyrolyzed at varying temperatures (300, 400, 500, and 600 °C) to produce different types of biochar, which were subjected to physio-chemical, proximate, and ultimate analyses. Distinctive variations were observed in the characteristics of the used feedstock types and their derived biochars. The biochars derived from CC exhibited the highest pH (8.41–11.02), while the biochars derived from CH demonstrated the minimum pH (7.99–8.40). Overall, the biochars derived from PL, CC, TM, and DL showed higher contents of C as compared to the other biochars, suggesting higher stability. Contrarily, the biochars derived from CH and CD exhibited a higher labile C fraction, indicating its lower recalcitrance than other tested biochars. The biochars produced at low pyrolysis temperatures showed a comparatively amorphous surface with lower alkalinity and electrical conductivity, while higher moisture, net negative charge, labile carbon, and volatile contents. Contrarily, the higher pyrolysis temperature demonstrated the higher ash and fixed carbon contents with more surface porosity and comparatively higher non-labile carbon fraction. Biochar produced at 600 °C exhibited H/C and O/C atomic ratios of <0.2, suggesting higher stability and recalcitrant potential against biochars produced below 500 °C, which showed H/C and O/C atomic ratios in the range of 0.2–0.4.

Environmental Risk from Organic Residues

Soil nutrient imbalance is a global threat to food security and ecosystem sustainability but adding organic residues or constructing anthropogenic soils and technosols can optimize it. However, FAO considers organic residues not “risk-free”, mainly due to their heavy metal content. Despite the fact that applying pruning residues to soil is a worldwide fertilization practice, its potential heavy metal risk has been poorly studied. This work characterizes Cu, Zn, Cd, Cr, Ni and Pb elemental composition concentration and their solubility content in almond tree pruning, commercial peat substrate, hay straw, olive tree pruning, pomegranate peel, pine needle, date palm leaf pruning, sewage sludge compost and vine pruning. Furthermore, we compare the legal frameworks governing heavy metal content in agricultural substrates to heavy metal concentration in each residue. Results show that commercial peat substrate is the only one among those studied that surpasses the threshold value for Cr in agricultural substrates. All pruning residues met the heavy metal threshold value; hence, their application to soil involves minimal soil toxicity. Moreover, the solubility index of heavy metals and the maximum quantity of each residue are crucial to discerning a heavy metal-free organic fertilization plan.