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Article

Exploitation of Plastic and Olive Solid Wastes for Accelerating the Biodegradation Process of Plastic

by
Hassan Y. Alfaifi
1,
Sami D. Aldress
2 and
Basheer A. Alshammari
3,*
1
Waste Management and Recycling Technologies Institute, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
2
Refining and Petrochemical Technologies Institute, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
3
Advanced Materials Technologies Institute, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
*
Author to whom correspondence should be addressed.
J. Compos. Sci. 2025, 9(8), 445; https://doi.org/10.3390/jcs9080445
Submission received: 16 June 2025 / Revised: 4 August 2025 / Accepted: 14 August 2025 / Published: 18 August 2025
(This article belongs to the Section Biocomposites)
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Versions Notes

Abstract

Recently, plastic and agricultural waste have gained attention as sustainable alternatives. Despite efforts to recycle these materials, much still ends up in landfills, raising environmental concerns. To optimize their potential, these wastes ought to be transformed into value-added products for diverse industrial applications. This work focused on producing thin composite material films using olive oil solid waste called JEFT and recycled plastic bottles. JEFT was cleaned, dried, and processed mechanically via ball milling to produce nano- and micron-sized particles. Composite films were produced via melt compounding and compression molding with a rapid cooling process for controlled crystallinity and enhanced flexibility. Their density, water absorption, tensile strength, thermal stability, water permeability, functional groups, and biodegradation were comprehensively analyzed. Results indicated that 50% JEFT in recycled plastic accelerated thermal deterioration (42.7%) and biodegradation (13.4% over 60 days), highlighting JEFT’s role in decomposition. Peak tensile strength (≈32 MPa) occurred at 5% JEFT, decreasing at higher concentrations due to agglomeration. Water absorption and permeability slightly increased with JEFT content, with only a 1% rise in water permeability for 50% JEFT composites after 60 days. JEFT maintained the recycled plastic’s surface chemistry, ensuring stability. The findings of this study suggest that JEFT/r-HDPE films show potential as greenhouse coverings, enhancing crop production and water efficiency while improving plastic biodegradation, offering a sustainable waste management solution.

1. Introduction

The olive oil industry has experienced significant growth over the past two decades due to rising demands and favorable market conditions [1]. The process of oil extraction, i.e., separating the oil from olives, releases significant greenhouse gases (GHGs) and produces considerable amounts of solid and liquid waste by-products. Commonly referred to as olive pomace, olive cake, olive oil residue, or olive husk, this solid waste comprises seeds and residual pulp and accounts for up to 30–40% of the output from this process [2,3]. The annual global production of olive pomace is approximately 1300 million tons and is projected to reach 2200 million t by 2025 [4]. This waste consists of a lignocellulosic matrix (≈31% cellulose, ≈23% hemicelluloses, and ≈26% lignin), along with phenolic compounds, acids, and oily residues. Consequently, olive oil waste can be viewed as an economic asset that can be transformed into valuable products, offering sustainable solutions to the persistent problem of waste disposal [5].
Multiple studies have explored the utilization of olive oil waste or olive pomace, derived from continuous or discontinuous extraction processes, in diverse applications such as combustion, biorefinery, livestock feeding, and soil amendments [6,7]. For instance, Najafi et al. [8] explored the potential of olive waste in a multi-product biorefinery, employing various pretreatment methods on different olive waste components for bioconversion into biogas, bioethanol, and lignin. The study demonstrated the energy recovery potential from olive waste by observing increases in methane and bioethanol yields from specific pretreatments and residual oil extraction for biodiesel production. Ameixa et al. [9] explored the potential of black soldier flies to bio-convert olive pomace into animal protein. The results indicated that higher levels of olive pomace in diets extended larval development times and impacted feed conversion rates, yet they improved the fatty acid profile of the larvae, making them richer in monounsaturated fats. These findings suggest that black soldier flies can effectively convert olive pomace into a sustainable feed alternative, enhancing protein content and altering fatty acid compositions beneficially. Moreover, Alaoui et al. [10] reviewed the environmental impact of olive oil production, emphasizing the potential of olive pomace as a sustainable soil amendment. Olive pomace was found to improve soil fertility, structure, and moisture capacity, particularly in Mediterranean regions with poor soil conditions. Similarly, Ameziane et al. [11] investigated the effects of using various concentrations of olive pomace on the growth of fava beans and lentils in Morocco. The results showed that olive pomace, particularly at 10, 15, and 25% concentrations, significantly improved seed germination and various growth parameters for both crops, such as leaf number, stem size, leaf area, dry matter weight, seedling vigor, and germination rate compared to control soil. However, limitations were encountered due to the high moisture and chlorine content of the waste. Therefore, managing these large quantities of residues presents substantial challenges due to their high phytotoxicity and potential as pollutants and the costs associated with proper disposal treatments [12,13]. For example, a substantial amount of olive oil waste is burned in fields post-harvest to clear land for subsequent crops, a practice necessitated by labor constraints, yet resulting in nutrient loss and increased carbon dioxide (CO2) emissions [14,15].
The olive industry has started expanding into new climatic regions outside the Mediterranean basin, which is driven by growing demand for extra virgin olive oil [16]. This is exemplified by the Kingdom of Saudi Arabia (KSA), where olive cultivation has escalated to over 5 million trees, producing 80,000 t annually in the Al-Jouf and Tabuk regions [17]. This surge in production leads to considerable agricultural waste, posing environmental challenges. However, a study by Khdair et al. [18] suggested that while olive oil wastes do not affect soil properties, there is a critical need for regulations and new technologies to manage and utilize these wastes effectively in industrial applications.
In parallel with olive oil waste, plastic waste has become a significant environmental challenge in the KSA, where large amounts of plastic are produced and discarded annually. Since the introduction of plastics, these materials have played a crucial role in enhancing modern lifestyles due to their versatility and durability. However, their widespread use has led to an alarming accumulation of non-biodegradable waste in landfills. A study by Islam et al. [19] estimated that KSA generates over 800,000 tons of plastic waste from water bottles annually, with approximately 500,000 tons ending up in landfills, contributing to 2.6 million tons of CO2 emissions per year. To mitigate this issue, KSA has implemented regulatory measures banning non-biodegradable plastics, particularly in packaging materials, as such composites usually demonstrate a strong antioxidant potential [20,21]. In response, several plastic manufacturers have begun developing biodegradable and cost-effective plastic alternatives to reduce environmental pollution and shorten the lifespan of plastic waste in its final disposal stage [22,23,24].
Among the hundreds of thousands of tons of plastics discarded into the environment annually is polyethylene (PE), such as HDPE, notable for its widespread application in packaging, containers, bottles, and pipeline. Such material is essential for numerous applications owing to its characteristics, including high molecular weight, semicrystalline structure, significant hydrophobicity, minimal biodegradability, and its environmental persistence. Consequently, it constituted significant environmental waste materials. HDPE is one of the largest contributors to plastic waste pollution issues. These wastes not only pose challenges to the natural environment but also effects local populations, infrastructure, and tourism, leading to health issues. The combination of recycled HDPE plastics with other materials, recognized for improving their mechanical strength, into practical applications is a feasible, effective, and sustainable approach to waste management and plastic pollution mitigation [25,26,27].
To address the growing concerns surrounding both olive oil and HDPE plastic waste, researchers have explored innovative solutions that integrate these materials into sustainable applications. Past studies have investigated the incorporation of olive pomace waste into polymer composites, emphasizing fabrication techniques, characterization methods, and potential industrial applications. For instance, Hamida et al. [28] explored the incorporation of olive stone flour into polystyrene composites at different weight ratios (0–30%). The findings indicated that as the filler content increased, the hardness of the composites rose, while both tensile strength and elongation at break diminished, primarily attributed to inadequate filler dispersion and interfacial bonding. Similarly, olive stone flour was tested as a filler in polyvinyl chloride and polypropylene composites [29,30]. Their findings revealed that while the addition of olive stone improved stiffness and reduced water absorption, it also reduced tensile strength and impact resistance, indicating the need for coupling agents to enhance adhesion. From a broad perspective, the primary challenge faced when integrating natural lignocellulose materials into polymers is interfacial adhesion. Hejna et al. [31] compared olive stone, date seed, and wheat bran as bio-composite fillers in poly(ε-caprolactone) matrices, showing that olive stone-reinforced composites had the highest hardness and improved thermal stability compared to the other fillers. Additionally, previous research has examined the chemical composition of olive pomace waste and its economic feasibility for waste management [32,33].
A review by Valvez et al. [34] highlighted the potential of olive stone residues as fillers in polymeric composites, improving stiffness but limiting strength; however, further efforts are required to fully understand their mechanical behavior, particularly in terms of fracture and fatigue properties. Given the pressing need for cost-effective and sustainable solutions using locally available waste resources, this study focuses on the development of novel polymeric composite films as potential greenhouse covering and packaging materials. These composite films, derived from olive oil solid waste and bottle wastes, aim to enhance biodegradation under KSA’s atmospheric conditions. The developed composite materials were subjected to a comprehensive characterization process, evaluating their physical, chemical, thermal, and mechanical properties, including density, water absorption, tensile strength, thermal degradation, water permeability, surface chemistry, and biodegradation performance. The obtained findings are expected to provide valuable insights for decision-makers, supporting the implementation of sustainable waste management strategies and promoting the adoption of bio-based composite materials in industrial applications.
Notwithstanding this intriguing research, only a limited number of studies documented in the literature have focused on the utilization of olive oil solid waste as a filler in polymer-based composite materials and their final composite properties, particularly, the degradation rate. Considering the available recycled high-density polyethylene (r-HDPE) and olive solid waste (JEFT) amounts, manufacturing of polymer based-composites without compatibilizers or coupling agents could be a viable option for specific application in Saudi Arabia. There is considerable potential for such bio-composites’ environmentally friendly applications, including the development of packaging materials. In this study, the effects of the olive solid waste content on the density, water absorption, tensile strength, thermal stability, water permeability, chemical structure, and biodegradability properties of the final compounds (HDPE/JEFT) were investigated using a wide range of analytical techniques.

2. Materials and Methods

2.1. Substrate Sampling

The composite materials were prepared using milk bottles as the recycled polymer matrix, as shown in Figure 1a. These bottles are made from high-density polyethylene (HDPE) (according to recycling symbols), hereinafter abbreviated as r-HDPE. The olive oil waste was sourced from a local olive oil processing plant in the Al-Jouf region in 2022 and used as the reinforcing agent, as shown in Figure 1b. Prior to use, the olive oil waste underwent purification, which involved soaking in distilled water overnight to remove excess oil and dirt. In this study, the purified olive oil waste is referred to as JEFT. There is no coupling agent used in this work.

2.2. Preparation of Composite Films

To prepare the composite films, the JEFT samples were first soaked, washed, and then dried at 70 °C for 24 h until a stable weight was achieved. The dried waste was then subjected to mechanical treatment using a ball-milling machine to obtain finer particles. The treated samples were stored at 25 °C for further utilization, including fabrication and characterization. Figure 2 presents images of JEFT residue with different particle sizes after mechanical treatment. Before any processing or characterization, both JEFT and r-HDPE were dried again in a vacuum oven at 70 °C for 24 h to ensure moisture removal.
To fabricate the composite materials, the JEFT and r-HDPE components were manually premixed to ensure uniform JEFT particle distribution within the recycled plastic before compounding. The melt compounding technique was then employed to develop JEFT/r-HDPE composite samples with the following loading ratios: 0/100, 5/95, 10/90, 15/85, 20/80, 25/75, and 50/50 wt.% (JEFT/r-HDPE), as displayed in Table 1. The compounding process was conducted using a Minilab co-rotating twin-screw extruder, operating with a screw speed of 100 rpm at 180 °C for 10 min. After extrusion, the composite materials were cooled in an ice-water bath and then dried before undergoing molding. The extruded composites were then processed into films (~0.1 mm thick) using compression molding at 190 °C under a pressure of 50 kN for 5 min, followed by an additional 2 min compression at the same temperature and pressure. This was followed by rapid cooling at a rate of ~20 °C/min and subsequent drying in a vacuum oven at 40 °C for 24 h. Figure 3 presents the different JEFT/r-HDPE composite film samples developed in this study. The prepared films were then stored for characterization and analytical testing.

2.3. Analytical Testing

2.3.1. Density

The bulk density of the composite material films was determined according to ASTM D792-13 by using Archimedes’ principle. Several specimens of about 1.0 g of each composite were cut randomly and immersed into the cylinder containing distilled water. Afterward, displacement of water volume was observed, and the density of the JEFT/r-HDPE composites was calculated as follows: ρ   is the density (g/cm3), m is the mass (g), and v is the volume (cm3).
ρ = m v

2.3.2. Water Absorption

The water absorption of the JEFT/r-HDPE composites was analyzed as per ASTM D570-98. Prior to testing, three specimens of each sample were oven-dried at 50 °C to remove any residual moisture. The dried samples were then immersed in distilled water at 25 °C for 24 h and subsequently removed at regular time intervals. After removal, the samples were wiped with tissue paper to remove excess surface water and weighed using a high-precision scale every 24 h for a period of two weeks. The recorded weight changes were used to calculate the percentage of water absorption, allowing for the assessment of the composites’ moisture uptake behavior over time using the following formula:
W b = M 0 − M t M t × 100 %
where W b is the water absorption (%), M 0 is the initial dried mass (g), and M t is the final wet mass (g).

2.3.3. Tensile Test

The tensile properties of the JEFT/r-HDPE composites were evaluated according to the ASTM D638-19 standard using a universal testing machine (Instron 5544, Norwood, MA, USA) equipped with a 5 kN load cell. Dog bone-shaped specimens of each composite formulation were tested by keeping the crosshead speed of about 1 mm/min at room temperature while keeping the humidity at 50 ± 5% for 24 h. The tensile stress at yield, tensile strength, and elongation at break were measured and analyzed to assess the mechanical performance of the developed composites. Five specimens of each sample were tested for tensile test, and the average values were reported.

2.3.4. Thermal Characterization

The thermal behavior of the composites was analyzed using a thermogravimetric analyzer (TGA 1, PerkinElmer, Shelton, CT, USA). Each sample was heated gradually from 25 °C to 800 °C at a heating rate of 10 °C/min. The thermal decomposition temperatures and weight loss were determined from the weight–temperature curves to assess the thermal stability of the composites. The thermogravimetric test was conducted under a nitrogen atmosphere to prevent oxidative degradation during heating. Three specimens of each sample were tested for thermal stability, and the average values were reported.

2.3.5. Permeability Test

The permeability of the composite films was evaluated following the ASTM E96-95 standard under ambient chamber conditions, with a relative humidity of 35% ± 5% at room temperature [35,36]. Three circular specimens (~30 cm2 in area) were cut from each sample. Each specimen was placed over a cup containing 40 mL of distilled water, sealed using silicone rings, and then enclosed in hermetically sealed jars to maintain controlled test conditions (Figure 4). The cups were periodically weighed using an analytical balance, and the water permeability values were calculated using regression analysis of the weight loss versus time data. The weight loss was determined by subtracting the loss through the sealing from the total weight loss. Three replicates of each film were tested to ensure reliability.

2.3.6. Functional Group Characterization

Fourier-transform infrared (FTIR) spectroscopic measurements were conducted using a Nicolet 5700 FTIR spectrometer (Thermo Electron Corporation, Waltham, MA, USA). Three specimens of each sample were prepared by mixing with dried potassium bromide (KBr) (Fisons Scientific) to form KBr pellets for analysis. Prior to mixing, the samples were dried at 120 °C overnight to remove any residual moisture. The dried samples were then ground and mixed with KBr (1 mg sample with 220 mg KBr) for several minutes until a fine powder was obtained. The FTIR spectra were recorded over the 400–4000 cm−1 wave number range to identify functional groups present on the film surfaces. This analysis was performed to assess the modifications in JEFT after acid treatment.

2.3.7. Biodegradation Investigation

The soil burial test is a widely used method for assessing the biodegradability of polymeric materials. The examination was conducted in accordance with the methodology outlined by Alshabanat et al. [37]. In this study, the test was conducted in a flower container filled with farmland sand, sourced from a private garden in Riyadh, where the samples were exposed to natural weather conditions, including temperature variations, sunlight, humidity, and wind. Three rectangular specimens of each sample (20 × 40 × 0.1 mm3) were cut, washed with distilled water, and then dried overnight at 25 °C before testing. The dried samples were weighed and buried at a depth of ~10 cm in the soil for 60 days, starting from 1 April 2021. The garden was watered daily in the morning to simulate real environmental conditions. The biodegradability of the samples was assessed by calculating the percentage weight loss over the burial period, using the following formula:
W L = W 0 − W t W t × 100 %
where W L is the weight loss (%), W 0 is the initial weight (g), and W t is the final weight (g).

2.3.8. Scanning Electron Microscopy (SEM)

Scanning Electron Microscopy (SEM) is an extensively utilized imaging method that delivers high-resolution surface morphology through the scanning of samples with a focused electron beam. This study necessitates a thorough analysis of microstructures and surface features. In this study, the fractured surface morphology of the samples was examined using a scanning electron microscope model (SEM, Jeol JSM-6010PLUS/LV, Peabody, MA, USA) operated at an acceleration voltage of 15 kV. Before imaging, the composite samples were coated with a thin layer of gold to enhance conductivity. A small amount of JEFT was dispersed in ethanol, then sonicated for about 15 min, and dropped on the conductive carbon tape attached to the sampling stub.

3. Results and Discussions

3.1. Density Measurements

Figure 5 illustrates the density values of composite material films, highlighting the influence of JEFT filler concentration on the r-HDPE matrix. Generally, the density of the composites does not exhibit a significant increase as the JEFT content rises from 5 to 50 wt.%. However, a gradual decrease in density is observed between 10 and 50 wt.% JEFT content. This trend can be attributed to the higher JEFT content, which increases the bulkiness of the composite material. The increased bulkiness expands the overall volume, ultimately leading to a reduction in composite density. To the best of the author’s knowledge, no prior studies have specifically measured the density of JEFT-reinforced polymer composites. However, Banat [38] conducted a review listing the measured properties of olive pomace-reinforced polymer composites, providing a relevant reference for comparative analysis.

3.2. Moisture Content Behaviors

Figure 6 illustrates the water uptake behavior of the composite films as a function of exposure time under various immersion conditions and JEFT loadings. The results indicated that water absorption increases with higher JEFT filler content, particularly after 24 h of immersion. During the initial stages of absorption, the water content increased gradually. It is expected that with extended immersion time, a saturation plateau will be reached at JEFT loadings exceeding 50 wt.%. This trend is well-documented in natural fiber-reinforced polymer composites, where the hydrophilic nature of natural fillers contributes to increased water absorption. These observations agree with previous published studies that reported similar behavior [39,40].

3.3. Tensile Properties

Figure 7 demonstrates the tensile strength of the composite material. The tensile strength of JEFT/r-HDPE composites exhibited an initial increase at 5 wt.% JEFT content, followed by a gradual decline with further JEFT loading (blue curve). This decrease in strength is likely attributed to weak interfacial bonding between the r-HDPE matrix and JEFT filler, which becomes more pronounced as JEFT content increases. Additionally, higher JEFT concentration may lead to increased void formation and poor dispersion, further contributing to the reduction in overall composite strength. Similar trends have been reported for olive pomace-reinforced polypropylene composites [32], as well as in other studies on polymer composites containing olive oil solid waste [33,38,40].
Similarly, the elongation properties of r-HDPE/JEFT composites tend to decrease as JEFT content increases (black curve). This decline is likely due to the presence of JEFT within the r-HDPE matrix, which disrupts the bonding and intermolecular structure of the polymer. As a result, the composite exhibits reduced flexibility, impairing its ability to stretch and return to its original form. Given this behavior, JEFT/r-HDPE composites may not be suitable for applications where elongation is a critical parameter. However, Sawalha et al. [41] reported enhancements in tensile properties when olive oil waste-reinforced recycled HDPE was subjected to carbonization at different temperatures. Their findings suggested that pre-treating JEFT could improve adhesion between JEFT and r-HDPE, leading to better dispersion and reduced agglomeration effects, ultimately enhancing the mechanical properties of the composite. The pre-treating process usually uses coupling agents, such as maleic anhydride-grafted polyethylene, that efficiently improve the compatibility between the r-HDPE and natural filler, then enhance the dispersion of natural filler into the r-HDPE matrix, and create chemical bonding between the modified JEFT and r-HDPE matrix (interfacial bonding). Commonly, interfacial bonding can happen in four different bondings or interlockings: (a) mechanical, (b) chemical, (c) molecular interdiffusion, and (d) electrostatic. Chemical bonding can significantly remove lignin and hemicellulose from the fiber, leading to enhanced hydrogen bonding and improved mechanical properties. The outcomes of the tensile strength often showed enhancements in the compatibilized polymer composites compared to the un-compatibilized one. A state-of-art review on progress and challenges in sustainability, compatibility, and production of eco-composites has been published by Nassar et al. [42], who claimed that the surface functionalization of both the polymer matrix and natural filler is anticipated to garner the interest of researchers in the forthcoming years. Consequently, additional research is necessary to investigate novel modification techniques to attain optimal interfacial bonding between the matrices and fillers.

3.4. Thermal Properties

To reduce the effects of oxidative degradation, TGA scans were conducted under a nitrogen atmosphere to examine the thermal degradation behavior of pure JEFT and JEFT/r-HDPE composites. Natural fillers are highly sensitive to thermal degradation [43]; therefore, evaluating the thermal stability of the newly developed JEFT-based r-HDPE composites is crucial, as thermal degradation can significantly alter the color and properties of the final product. The TGA results for JEFT filler and its composites under a nitrogen atmosphere are presented in Figure 8 and Figure 9, respectively. JEFT filler remained thermally stable up to approximately 200 °C, with a 5% weight loss, primarily attributed to moisture evaporation. In contrast, r-HDPE exhibited greater thermal stability, undergoing thermal degradation at around 450 °C, with less than 5% weight loss due to moisture release [4]. These findings highlight the significant difference in thermal behavior between JEFT and r-HDPE, reinforcing the importance of optimizing the composite’s thermal stability for potential industrial applications.
The TGA results indicate that all composite samples exhibited minimal weight loss up to around 300 °C. Beyond this temperature, a significant increase in weight loss occurs over a narrow temperature range, as reflected in the steep slopes of the TGA curves. However, the onset temperature for thermal degradation varies among the samples, as shown in Figure 9.
A common method for evaluating thermal stability involves determining the temperature at 5% weight loss (T5%) and the thermal decomposition temperature. The T5% values of the examined composites are presented in Table 2. The findings indicate that thermal stability decreases with increasing JEFT content in the r-HDPE matrix, likely due to the lower thermal resistance of JEFT compared to r-HDPE.
Generally, the thermal degradation of the JEFT/r-HDPE composites occurs in three distinct stages. The first stage, which takes place between 25 and 200 °C, corresponds to the evaporation of moisture, a characteristic commonly observed in natural fiber-reinforced polymer composites. This stage is associated with minimal weight loss, primarily due to the release of absorbed water within the composite structure. The second stage, occurring between 200 and 350 °C, is shorter and marks the degradation of the polymer matrix chains and hemicellulose, which are among the most thermally sensitive components in natural fillers. A maximum weight loss of approximately 30% was observed in composites containing 50 wt.% JEFT, indicating that hemicellulose degradation plays a significant role in the structural breakdown of the material. The third stage, which occurs between 350 and 500 °C, is attributed to carbonization within the polymer and the thermal decomposition of lignin and cellulose. At this point, weight loss continues as the polymer matrix further degrades. Beyond 500 °C, all composite samples exhibit no significant weight loss up to 800 °C, indicating that the remaining material consists primarily of char residue (carbonaceous residue) produced during the earlier decomposition phases. As observed in Figure 9 and Table 2, the amount of char residue increases with higher JEFT content, suggesting that JEFT incorporation contributes to greater thermal stability at elevated temperatures.
The thermal degradation behavior observed in this study aligns with previous findings. Banat et al. [44] and Kaya et al. [32] have reported similar three-step degradation processes in olive oil pomace-reinforced HDPE and polypropylene composites, respectively. These results confirm that natural fiber-based polymer composites exhibit a multi-stage degradation process, influenced by the presence of moisture, hemicellulose decomposition, and final carbonization. Understanding these thermal degradation characteristics is crucial for optimizing the processing and application of JEFT/r-HDPE composites, particularly in high-temperature environments where thermal stability is a key performance parameter.

3.5. Permeability Results

The water permeability of polymer composite materials is a critical factor in various applications, including packaging, membrane technology, and protective coatings or sheets. The water permeation process in these materials is inherently complex, influenced by multiple factors such as the polarity of water molecules, their interaction with polymer chains, hydrogen bonding capacity, and the resulting effects on polymer swelling and chain mobility. To predict water permeation behavior, several theoretical models have been developed, incorporating parameters such as tortuosity, geometry, crystallinity, temperature, filler particle orientation, weight/volume fraction, and polymer chain confinement. Understanding water permeability is particularly important in this study, as the long-term objective is to develop composite films for greenhouse coverings and packaging applications, where the ability to control permeability is essential for functional performance in diverse environmental conditions [45].
Figure 10 shows the water permeability results for the composites. The water permeability of the investigated composite films was found to be very low, as expected for pure recycled bottle-based materials, but it showed a slight increase with increasing JEFT loading. For instance, films containing 50 wt.% JEFT exhibited only a ~1% increase in permeability, indicating that water transport primarily occurs along the surface of JEFT particles.
Gårdebjer et al. [33] reported that the presence of hemicellulose contributes to higher permeability in composite films, which could explain the observed trend. Several approaches have been explored to enhance the permeability of polymer composites, such as reducing the filler volume fraction, modifying the filler, or developing hybrid composites [34]. For example, Jin et al. [46] suggested that incorporating graphene nanomaterials can improve the permeability of polymer nanocomposites due to their high aspect ratio and large surface area, which enhances reinforcement effects. Additionally, improving adhesion properties and filler dispersion between JEFT and r-HDPE could enhance the water barrier properties of the composite films. JEFT agglomeration may act as a stress concentrator, leading to the formation of microcracks, which could eventually merge and cause fractures or failures in the JEFT/r-HDPE composites, as observed in the tensile properties (Figure 7).

3.6. Functional Group Analysis

Compared to the nearly featureless spectrum observed for all JEFT/r-HDPE composites, Figure 11 reveals three strong absorption peaks around 3000 cm−1, 1500 cm−1, and 750 cm−1, corresponding to the hydroxyl (-OH), carbonyl (C=O in carboxyl, -COOH), and C-H functional groups, respectively. This indicates that all composite samples exhibit similar functional groups, suggesting that JEFT does not significantly alter the surface chemistry of the r-HDPE matrix. This characteristic is beneficial for applications such as greenhouse covering materials, as it ensures chemical stability with no undesired changes to the surface properties of the films.
A similar presence of functional groups has been reported in comparable polymer composites and various agricultural waste-based materials [47]. Additionally, previous studies have highlighted that the key constituents of JEFT offer excellent potential for natural ultraviolet (UV) protection in composite films [48,49]. This reinforces the suitability of JEFT-based materials for specific applications, particularly where UV resistance and environmental stability are critical factors, such as in packaging materials.

3.7. Biodegradation Analysis

The weight loss of buried composite films serves as a key indicator of the biodegradation process of the investigated samples. To better understand the biodegradation mechanism and the factors influencing this process, biodegradation can be defined as the natural breakdown of a material into its basic components through microbial activity and environmental interactions (biological activities) [50,51]. The biodegradation rate of composite materials is influenced by the characteristics of their components, the strength of their bonding, and the environmental circumstances, such as temperature, moisture, soil pH, microbial population, and nutrient availability. The degradation also can be defined as “a biochemical transformation of the composition of the material tested by microorganisms and the tendency of a material to decompose into its constituent molecules through natural processes,” as articulated in an earlier published study [52]. The biodegradation of plastics in soil transpires both aerobically and anaerobically, yielding H2O and CO2 during aerobic degradation, or CH4 during anaerobic degradation. The degrading process is termed mineralization when these ultimate products are acquired. The carbon in polymers is converted to carbon biomass prior to mineralization, which is used by microbes for growth. Biological activities occur at the interface between the composite and soil; hence, the surface area and characteristics of the exposed surface are crucial [52,53].
A surface abundant in polar hydrophilic functional groups is significantly more susceptible to biodegradation than hydrophobic surfaces [54,55]. JEFT’s hydrophilicity and enhanced biodegradability augment microbial adherence to the composite material, hence promoting the degradation process. A recent review on environmental degradation of polymer composites with natural fillers has been published by Brebu et al. [56], who presented some characteristics found in the literature related to the effect of factors such as temperature, mechanical forces, solar radiation, humidity, and biological attacks on the properties of polymer composites containing different natural fillers.
Table 3 presents the weight loss of JEFT/r-HDPE composite samples as a function of burial days. The weight loss percentage of the composite films after 60 days of soil burial varied among the samples. The r-HDPE exhibited significantly lower weight loss compared to the JEFT/r-HDPE composites, indicating that JEFT enhances the biodegradability of the material. The highest recorded weight loss was observed in samples containing 50 wt.% JEFT, which degraded by 13.4% over 60 days, whereas pure r-HDPE exhibited only 0.1% degradation during the same period.
The biodegradation process in soil burial conditions is a biochemical conversion, where microorganisms break down complex polymer structures into simpler molecules through natural degradation pathways. A comprehensive review by Sadeghifar et al. [48] explored the mechanisms, influencing factors, and key parameters involved in the biodegradation of plastics, further emphasizing the role of organic fillers like JEFT in accelerating polymer degradation. These findings suggest that incorporating JEFT into r-HDPE enhances the material’s environmental sustainability, making it a promising alternative for biodegradable composite applications.
Given the observed material properties, particularly the modest mechanical strength at low JEFT concentrations, improved biodegradation, and slight increases in water permeability, the JEFT/r-HDPE composite films appear well-suited for use in sustainable packaging applications, particularly for short-life or single-use items. Packaging materials benefit from good dimensional stability, sufficient barrier properties, and preferably some level of biodegradability. Our 5–10% JEFT composites demonstrated tensile strengths close to ~32 MPa with only minimal increases in water permeability, making them viable candidates for lightweight packaging formats that do not demand heavy structural integrity [32,33,40].
Importantly, incorporating JEFT as a filler contributes significantly to the environmental value of the composite. As packaging accounts for a large portion of plastic waste globally, using bio-sourced, degradable fillers like olive pomace can help reduce the environmental burden of plastic disposal. Our results showed up to 7% degradation at 25% JEFT and 13.4% at 50% JEFT in 60 days, suggesting that even partial filler inclusion can meaningfully enhance end-of-life sustainability [48,56]. Although increasing JEFT content compromises strength beyond certain limits, the performance at lower concentrations remains acceptable for secondary packaging, liners, wrapping films, and other non-load-bearing applications where disposal convenience and sustainability are priorities [25,31].
Moving forward, the packaging potential of these composites could be further enhanced through the use of compatibilizers like maleic anhydride-grafted polyethylene, which would strengthen filler–matrix bonding and improve load distribution. Surface treatment of JEFT may also address the current dispersion and adhesion issues noted at higher filler loadings [41,42]. Nonetheless, even without such modifications, the current formulation provides a cost-effective, partially biodegradable solution for low-demand packaging needs, offering both waste valorization and plastic footprint reduction in line with modern circular economy practices [22,23,48]. Focusing the discussion solely on this application allows for a clearer understanding of the material’s practical potential and a more targeted direction for future research and industrial integration.

3.8. Morphology Observation

Figure 12 displays the SEM images of purified JEFT, r-HDPE, and the fractured surfaces of JEFT/r-HDPE composite film samples mixed with different amounts of JEFT filler. The figure revealed different fractographic features. The sample of neat r-HDPE had flat surface morphology with wrinkle-like and ductile behavior features with free air voids, as shown in Figure 12a. This was due to the asymmetrical interaction between polymeric chains. In general, a rough, fractured surface indicates more ductility with the deformation of the matrix during tensile loading, whereas a smooth surface indicates more brittle fracture and lower fracture toughness. Conversely, Figure 12b represents the morphology of the JEFT, which apparently showed irregular particle shapes. The assumption that spherical particle shapes can be obtained is unrealistic, as JEFT particles typically exhibit complex shapes. The interfacial tension between polymer and filler plays a crucial role in determining phase morphology.
The morphology of the filler at all JEFT loading levels (Figure 12c–f) shows slight variations compared to that of the neat r-HDPE polymer matrix. Low-level pullout was noted at a low loading of JEFT (5 wt.%), indicating a relatively strong tensile stress at break performance of the r-HDPE composite in comparison to pure r-HDPE. At medium and high JEFT loading (10, 15, and 20 wt.%), more JEFT pullout, debonding, and more agglomerations states were observed. This was probably due to poor adhesion between JEFT and the r-HDPE polymer matrix. The presence of some agglomerations due to JEFT debonding is more pronounced in the r-HDPE composite containing 20 wt.% of JEFT. These morphological behaviors seem to agree with the results obtained in the tensile test in this study. These composites explain the lower mechanical strength and modulus with respect to the unfilled r-HDPE samples. As shown in Figure 7, the tensile strength of the r-HDPE composite initially increases up to 5 wt.% followed by a decline due to aggregation and poor adhesion between the matrix and fillers at higher loading. Banat et al. [38] observed a similar agglomeration effect at 25 wt.% of olive oil waste in an HDPE matrix. They suggested that to enhance the compatibilization between olive waste filler and HDPE polymer matrix, ~5% coupling agent should be used for successive polymer composites for packaging applications. Furthermore, it has already been established that unstable interfacial adhesion between natural filler and polymer matrix often results in fiber pull-out, fiber–fiber delamination, and matrix debonding, according to Sawalha et al. [41]. Comparative arguments were presented by other researchers who utilized olive stone as a filler for recycled high-density polyethylene and found that adhesion between the HDPE matrix and the olive stone waste was improved by using compatibilizers [57].

4. Conclusions

This research presents a sustainable solution for managing both agricultural and plastic waste in KSA by developing composite materials from olive oil solid waste (JEFT) and recycled plastic bottles (r-HDPE). The composite films were fabricated using a melt compounding process, followed by compression molding and rapid cooling, to produce thin and flexible films suitable for agricultural applications like general packaging and greenhouse covering materials. The developed films were subjected to different types of characterization to investigate their properties and performance. Increasing JEFT content resulted in lower composite density, contributing to lightweight materials. However, water absorption and permeability increased slightly with higher JEFT concentrations. Additionally, thermal degradation and biodegradation rates were faster in JEFT-containing films compared to pure plastic films, indicating improved environmental sustainability. Functional group analysis further confirmed that JEFT did not alter the surface chemistry of the r-HDPE matrix, maintaining the integrity of the polymer structure. According to the literature and these observations, the results highlight the potential of JEFT/r-HDPE composites as a sustainable bio-based material with good biodegradability, making them suitable for general packaging and greenhouse covering applications aimed at improving water and energy efficiency. The developed, partially green JEFT/r-HDPE polymer composite may serve as an alternative to traditional polymers in general packaging applications, particularly in amounts of JEFT as low as 50%.
Future research should focus on pre-treating JEFT, adding coupling agents like the maleic anhydride-grafted polyethylene, and optimizing the JEFT/r-HDPE ratio to enhance interfacial adhesion and improve the mechanical and functional properties of the final composite materials.
While the JEFT/r-HDPE composites may not yet rival the performance of conventional packaging plastics, this study offers a practical and accessible approach to turning agricultural and plastic waste into useful materials. By focusing on cost-effectiveness and partial biodegradability, it contributes meaningfully to the growing need for sustainable packaging solutions within a circular economy framework.

Author Contributions

B.A.A.: Methodology, writing of original draft, revising and editing the manuscript, analysis, interpretation of data, and supervision; H.Y.A.: Interpretation of data, resources, and reviewing the original draft; S.D.A.: Collection of data, review, discussion, and project administration. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by King Abdulaziz City for Science and Technology (KACST), Saudi Arabia.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

  1. Mili, S.; Bouhaddane, M. Forecasting Global Developments and Challenges in Olive Oil Supply and Demand: A Delphi Survey from Spain. Agriculture 2021, 11, 191. [Google Scholar] [CrossRef]
  2. Hung, Y.-T.; Kolla, S.N.; Paul, H.H.; Huhnke, C.R. Olive oil waste treatment: A review. World J. Adv. Res. Rev. 2024, 23, 1791–1795. [Google Scholar] [CrossRef]
  3. Akay, F.; Kazan, A.; Celiktas, M.S.; Yesil-Celiktas, O. A holistic engineering approach for utilization of olive pomace. J. Supercrit. Fluids 2015, 99, 1–7. [Google Scholar] [CrossRef]
  4. Ouazzane, H.; Laajine, F.; El Yamani, M.; El Hilaly, J.; Rharrabti, Y.; Amarouch, M.; Mazouzi, D. Olive mill solid waste characterization and recycling opportunities: A review. J. Mater. Environ. Sci. 2017, 8, 2632–2650. [Google Scholar]
  5. Azbar, N.; Bayram, A.; Filibeli, A.; Muezzinoglu, A.; Sengul, F.; Ozer, A. A review of waste management options in olive oil production. Crit. Rev. Environ. Sci. Technol. 2004, 34, 209–247. [Google Scholar] [CrossRef]
  6. Hassen, W.; Hassen, B.; Werhani, R.; Hidri, Y.; Jedidi, N.; Hassen, A. Processes of valorization and management of olive by-products: The pomace and olive mill wastewater. In Wastewater from Olive Oil Production: Environmental Impacts, Treatment and Valorisation; Springer: Berlin/Heidelberg, Germany, 2023; pp. 1–25. [Google Scholar]
  7. Ameziane, H.; Mabrouki, J.; Benchrifa, M.; Hmouni, D. Review of Olive Pomace Valorization Techniques: A Sustainable Perspective for the Olive Oil Industry. In Advanced Technology for Smart Environment and Energy; Springer: Berlin/Heidelberg, Germany, 2024; pp. 165–183. [Google Scholar]
  8. Najafi, E.; Castro, E.; Karimi, K. Biorefining for olive wastes management and efficient bioenergy production. Energy Convers. Manag. 2021, 244, 114467. [Google Scholar] [CrossRef]
  9. Ameixa, O.M.; Pinho, M.; Domingues, M.R.; Lillebø, A.I. Bioconversion of olive oil pomace by black soldier fly increases eco-efficiency in solid waste stream reduction producing tailored value-added insect meals. PLoS ONE 2023, 18, e0287986. [Google Scholar] [CrossRef]
  10. Alaoui, I.; El Ghadraoui, O.; Tanji, K.; Harrach, A.; Farah, A. The Olive Mill Pomace: A Sustainable Biofertilizer to Improve Soil Proprieties and Plant Nutrient Uptake. Waste Biomass Valorization 2024, 15, 2575–2590. [Google Scholar] [CrossRef]
  11. Ameziane, H.; Nounah, A.; Kabbour, M.; Khamar, M. Agronomic valuation of olive pomace obtained by different extraction systems. Ecol. Environ. Conserv. 2020, 26, 371–379. [Google Scholar]
  12. Pagnanelli, F.; Viggi, C.C.; Toro, L. Development of new composite biosorbents from olive pomace wastes. Appl. Surf. Sci. 2010, 256, 5492–5497. [Google Scholar] [CrossRef]
  13. Notarnicola, B.; Salomone, R.; Petti, L.; Renzulli, P.A.; Roma, R.; Cerutti, A.K. Life Cycle Assessment in the Agri-Food Sector: Case Studies, Methodological Issues and Best Practices; Springer: Berlin/Heidelberg, Germany, 2015. [Google Scholar]
  14. Roig, A.; Cayuela, M.L.; Sánchez-Monedero, M. An overview on olive mill wastes and their valorisation methods. Waste Manag. 2006, 26, 960–969. [Google Scholar] [CrossRef]
  15. Medouni-Haroune, L.; Zaidi, F.; Medouni-Adrar, S.; Kecha, M. Olive pomace: From an olive mill waste to a resource, an overview of the new treatments. J. Crit. Rev. 2018, 5, 1–6. [Google Scholar] [CrossRef]
  16. Conde-Innamorato, P.; Arias-Sibillotte, M.; Villamil, J.J.; Bruzzone, J.; Bernaschina, Y.; Ferrari, V.; Zoppolo, R.; Villamil, J.; Leoni, C. It is feasible to produce olive oil in temperate humid climate regions. Front. Plant Sci. 2019, 10, 1544. [Google Scholar] [CrossRef] [PubMed]
  17. Aly, A.A.; Hasan, Y.N.; Al-Farraj, A.S. Olive mill wastewater treatment using a simple zeolite-based low-cost method. J. Environ. Manag. 2014, 145, 341–348. [Google Scholar] [CrossRef]
  18. Khdair, A.; Abu-Rumman, G. Sustainable environmental management and valorization options for olive mill byproducts in the Middle East and North Africa (MENA) region. Processes 2020, 8, 671. [Google Scholar] [CrossRef]
  19. Islam, M.S.; Uddin, M.J.; Alshehri, K. Plastic waste and carbon footprint generation due to the consumption of bottled waters in Saudi Arabia. Res. Dev. Mater. Sci. 2018, 5, 000604. [Google Scholar] [CrossRef]
  20. Thapliyal, D.; Karale, M.; Diwan, V.; Kumra, S.; Arya, R.K.; Verros, G.D. Current status of sustainable food packaging regulations: Global perspective. Sustainability 2024, 16, 5554. [Google Scholar] [CrossRef]
  21. Saudi Standards. Technical Regulation for Degradable Plastic Products; Saudi Standards: Riyadh, Saudi Arabia, 2016; p. 24. [Google Scholar]
  22. Kaur, G.; Uisan, K.; Ong, K.L.; Lin, C.S.K. Recent trends in green and sustainable chemistry & waste valorisation: Rethinking plastics in a circular economy. Curr. Opin. Green Sustain. Chem. 2018, 9, 30–39. [Google Scholar] [CrossRef]
  23. Eygen, V.; Laner, D.; Fellner, J. Circular economy of plastic packaging: Current practice and perspectives in Austria. Waste Manag. 2018, 72, 55–64. [Google Scholar] [CrossRef]
  24. Eriksen, M.K.; Astrup, T.F. Characterisation of source-separated, rigid plastic waste and evaluation of recycling initiatives: Effects of product design and source-separation system. Waste Manag. 2019, 87, 161–172. [Google Scholar] [CrossRef]
  25. Tiago, G.A.; Mariquito, A.; Martins-Dias, S.; Marques, A.C. The problem of polyethylene waste–recent attempts for its mitigation. Sci. Total Environ. 2023, 892, 164629. [Google Scholar] [CrossRef]
  26. Gounden, K.; Mwangi, F.M.; Mohan, T.P.; Kanny, K. The use of recycled high-density polyethylene waste to manufacture eco-friendly plastic sand bricks. SPE Polym. 2024, 5, 20–34. [Google Scholar] [CrossRef]
  27. Lourmpas, N.; Papanikos, P.; Efthimiadou, E.K.; Fillipidis, A.; Lekkas, D.F.; Alexopoulos, N.D. Degradation assessment of high-density polyethylene (HDPE) debris after long exposure to marine conditions. Sci. Total Environ. 2024, 954, 176847. [Google Scholar] [CrossRef]
  28. Boussehel Hamida, M.A.; Nebbache, N.; Maou, S. Mechanical properties of polystyrene/olive stone flour composites. Res. J. Pharm. Biol. Chem. Sci. 2015, 6, 6. [Google Scholar]
  29. Naghmouchi, I.; Espinach, F.X.; Mutjé, P.; Boufi, S. Polypropylene composites based on lignocellulosic fillers: How the filler morphology affects the composite properties. Mater. Des. 2015, 65, 454–461. [Google Scholar] [CrossRef]
  30. Naghmouchi, I.; Mutjé, P.; Boufi, S. Olive stones flour as reinforcement in polypropylene composites: A step forward in the valorization of the solid waste from the olive oil industry. Ind. Crops Prod. 2015, 72, 183–191. [Google Scholar] [CrossRef]
  31. Hejna, A.; Sulyman, M.; Przybysz, M.; Saeb, M.; Klein, M.; Formela, K. On the correlation of lignocellulosic filler composition with the performance properties of poly (ε-caprolactone) based biocomposites. Waste Biomass Valorization 2020, 11, 1467–1479. [Google Scholar] [CrossRef]
  32. Kaya, N.; Atagur, M.; Akyuz, O.; Seki, Y.; Sarikanat, M.; Sutcu, M.; Seydibeyoglu, M.; Sever, K. Fabrication and characterization of olive pomace filled PP composites. Compos. Part B Eng. 2018, 150, 277–283. [Google Scholar] [CrossRef]
  33. Espadas-Aldana, G.; Guaygua-Amaguaña, P.; Vialle, C.; Belaud, J.-P.; Evon, P.; Sablayrolles, C. Life cycle assessment of olive pomace as a reinforcement in polypropylene and polyethylene biocomposite materials: A new perspective for the valorization of this agricultural by-product. Coatings 2021, 11, 525. [Google Scholar] [CrossRef]
  34. Valvez, S.; Maceiras, A.; Santos, P.; Reis, P.N. Olive stones as filler for polymer-based composites: A review. Materials 2021, 14, 845. [Google Scholar] [CrossRef]
  35. Gårdebjer, S.; Larsson, A.; Löfgren, C.; Ström, A. Controlling water permeability of composite films of polylactide acid, cellulose, and xyloglucan. J. Appl. Polym. Sci. 2015, 132, 41219. [Google Scholar] [CrossRef]
  36. Li, Y.; Xie, L.; Ma, H. Permeability and mechanical properties of plant fiber reinforced hybrid composites. Mater. Des. 2015, 86, 313–320. [Google Scholar] [CrossRef]
  37. Alshabanat, M. Morphological, thermal, and biodegradation properties of LLDPE/treated date palm waste composite buried in a soil environment. J. Saudi Chem. Soc. 2019, 23, 355–364. [Google Scholar] [CrossRef]
  38. Banat, R. Olive pomace flour as potential organic filler in composite materials: A brief review. Am. J. Polym. Sci. 2019, 9, 10–15. [Google Scholar]
  39. Abd Mohammed, A.; Depart, A. Study the thermal properties and water absorption of composite materials rrinforced with data and olive seeds. Iraqi J. Mech. Mater. Eng. 2015, 15, 138–152. [Google Scholar]
  40. Banat, R.; Fares, M.M. Olive oil waste filled high density polyethylene bio-composite: Mechanical, morphological and water absorption properties. Int. J. Compos. Mater. 2015, 5, 133–141. [Google Scholar]
  41. Sawalha, S.; El-Hamouz, A. Improvements of the tensile properties of recycled high density polyethylene (HDPE) by the use of carbonized olive solid waste. Polym. Plast. Technol. Eng. 2010, 49, 387–393. [Google Scholar] [CrossRef]
  42. Nassar, M.M.; Alzebdeh, K.I.; Pervez, T.; Al-Hinai, N.; Munam, A. Progress and challenges in sustainability, compatibility, and production of eco-composites: A state-of-art review. J. Appl. Polym. Sci. 2021, 138, 51284. [Google Scholar] [CrossRef]
  43. Abdulkarem, M.A.; Rasool, D.A.; Nabhan, B.J. Utilization of olive and pumice stones to improve the thermal properties of cement mortar. Int. J. Nanoelectron. Mater. 2020, 13, 181–188. [Google Scholar]
  44. Banat, R.; Fares, M.M. Thermo-gravimetric stability of high density polyethylene composite filled with olive shell flour. Am. J. Polym. Sci. 2015, 5, 65–74. [Google Scholar]
  45. Hu, X.; Chen, L.; Tao, D.; Ma, Z.; Liu, S. A facile pathway to modify cellulose composite film by reducing wettability and improving barrier towards moisture. Materials 2017, 10, 39. [Google Scholar] [CrossRef]
  46. Jin, J.; Rafiq, R.; Gill, Y.Q.; Song, M. Preparation and characterization of high performance of graphene/nylon nanocomposites. Eur. Polym. J. 2013, 49, 2617–2626. [Google Scholar] [CrossRef]
  47. Onuoha, C.; Onyemaobi, O.O.; Anyakwo, C.N.; Onuegbu, G.C. Effect Of Filler Loading And Particle Size On The Mechanical Properties Of Periwinkle Shell-Filled Recycled Polypropylene Composites. Am. J. Eng. Res. 2017, 6, 72–79. [Google Scholar]
  48. Sadeghifar, H.; Ragauskas, A. Lignin as a UV light blocker—A review. Polymers 2020, 12, 1134. [Google Scholar] [CrossRef]
  49. Wang, X.; Wang, S.; Liu, W.; Wang, S.; Zhang, L.; Sang, R.; Hou, Q.; Li, J. Facile fabrication of cellulose composite films with excellent UV resistance and antibacterial activity. Carbohydr. Polym. 2019, 225, 115213. [Google Scholar] [CrossRef] [PubMed]
  50. Usman, M.A.; Momohjimoh, I.; Gimba, A.S. Effect of groundnut shell powder on the mechanical properties of recycled polyethylene and its biodegradability. J. Miner. Mater. Charact. Eng. 2016, 4, 228. [Google Scholar] [CrossRef]
  51. Maraveas, C. Production of sustainable and biodegradable polymers from agricultural waste. Polymers 2020, 12, 1127. [Google Scholar] [CrossRef] [PubMed]
  52. Shah, A.A.; Hasan, F.; Hameed, A.; Ahmed, S. Biological degradation of plastics: A comprehensive review. Biotechnol. Adv. 2008, 26, 246–265. [Google Scholar] [CrossRef]
  53. Maran, J.P.; Sivakumar, V.; Thirugnanasambandham, K.; Sridhar, R. Degradation behavior of biocomposites based on cassava starch buried under indoor soil conditions. Carbohydr. Polym. 2014, 101, 20–28. [Google Scholar] [CrossRef]
  54. Arutchelvi, J.; Sudhakar, M.; Arkatkar, A.; Doble, M.; Bhaduri, S.; Uppara, P.V. Biodegradation of polyethylene and polypropylene. Indian J. Biotechnol. 2008, 7, 9–22. [Google Scholar]
  55. Zakaria, M.R.S.B.; Abid, M.B.; Shamim, A.; Suradi, S.S.; Marsi, N.B.; Kormin, F.B. A review on biodegradable composite films containing organic material as a natural filler. J. Inorg. Organomet. Polym. Mater. 2024, 35, 2126–2161. [Google Scholar] [CrossRef]
  56. Brebu, M. Environmental degradation of plastic composites with natural fillers—A review. Polymers 2020, 12, 166. [Google Scholar] [CrossRef]
  57. Pardalis, N.; Xanthopoulou, E.; Zamboulis, A.; Bikiaris, D.N. Olive stone as a filler for recycled high-density polyethylene: A promising valorization of solid wastes from olive oil industry. Sustain. Chem. Environ. 2024, 6, 100090. [Google Scholar] [CrossRef]
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Figure 1. Material used in this study: (a) used milk bottle and (b) as-received JEFT residue.
Figure 1. Material used in this study: (a) used milk bottle and (b) as-received JEFT residue.
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Figure 2. Images for different particle sizes of JEFT filler after the treatment. (a) <100 nm, (b) 150 μm and (c) 250 μm.
Figure 2. Images for different particle sizes of JEFT filler after the treatment. (a) <100 nm, (b) 150 μm and (c) 250 μm.
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Figure 3. Different JEFT/r-HDPE composite samples. (a) 15/85 wt.% of JEFT/r-HDPE, (b) Pure r-HDPE (transparent); 15/85 wt.%. of JEFT/r-HDPE (opaque) and (c) 50/50 wt.% of JEFT/r-HDPE.
Figure 3. Different JEFT/r-HDPE composite samples. (a) 15/85 wt.% of JEFT/r-HDPE, (b) Pure r-HDPE (transparent); 15/85 wt.%. of JEFT/r-HDPE (opaque) and (c) 50/50 wt.% of JEFT/r-HDPE.
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Figure 4. Permeability cup photo and prototype of the investigated samples.
Figure 4. Permeability cup photo and prototype of the investigated samples.
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Figure 5. Density values of the JEFT/r-HDPE composites. Note: Error bars are present but visually imperceptible due to extremely small standard deviations (≤±0.005 g/cm3).
Figure 5. Density values of the JEFT/r-HDPE composites. Note: Error bars are present but visually imperceptible due to extremely small standard deviations (≤±0.005 g/cm3).
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Figure 6. Water absorption of the JEFT/r-HDPE composites with different amounts of JEFT.
Figure 6. Water absorption of the JEFT/r-HDPE composites with different amounts of JEFT.
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Figure 7. Tensile properties of the JEFT/r-HDPE composites.
Figure 7. Tensile properties of the JEFT/r-HDPE composites.
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Figure 8. Thermogravimetric analysis curve of the JEFT filler.
Figure 8. Thermogravimetric analysis curve of the JEFT filler.
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Figure 9. Thermogravimetric analysis curve of the JEFT/r-HDPE composites.
Figure 9. Thermogravimetric analysis curve of the JEFT/r-HDPE composites.
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Figure 10. Water permeability of the JEFT/r-HDPE composites after 60 days. Note: Error bars are included but not visible at this scale due to very low variation (standard deviation ≤ ±0.01 g/cm2·day).
Figure 10. Water permeability of the JEFT/r-HDPE composites after 60 days. Note: Error bars are included but not visible at this scale due to very low variation (standard deviation ≤ ±0.01 g/cm2·day).
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Figure 11. Functional groups spectra of the JEFT/r-HDPE composites.
Figure 11. Functional groups spectra of the JEFT/r-HDPE composites.
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Figure 12. SEM images of pure epoxy composites. SEM images of (a) r-HDPE, (b) JEFT, and (c–f) JEFT/r-HDPE composites with different amounts of JEFT, i.e., 5, 10, 15, and 20 wt.%, respectively. Note: Scanning electron microscopy (SEM) images showing the sample morphology. The scale bar represents 100 nm, providing dimensional reference for size estimation.
Figure 12. SEM images of pure epoxy composites. SEM images of (a) r-HDPE, (b) JEFT, and (c–f) JEFT/r-HDPE composites with different amounts of JEFT, i.e., 5, 10, 15, and 20 wt.%, respectively. Note: Scanning electron microscopy (SEM) images showing the sample morphology. The scale bar represents 100 nm, providing dimensional reference for size estimation.
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Table 1. Various loading ratios of JEFT/r-HDPE composite samples.
Table 1. Various loading ratios of JEFT/r-HDPE composite samples.
Composite Samples # Loading Ratios of JEFT/r-HDPE in wt.%
Sample 1 0/100
Sample 2 5/95
Sample 3 10/90
Sample 4 15/85
Sample 5 20/80
Sample 6 25/75
Sample 7 50/50
Table 2. Thermal degradation temperatures (T5%) for the JEFT/r-HDPE composites.
Table 2. Thermal degradation temperatures (T5%) for the JEFT/r-HDPE composites.
JEFT wt.%T5% (°C)Residue (wt.%)
0480.3 ± 1.50.25
5475.8 ± 0.98.0
10466.5 ± 0.58.20
15330.7 ± 2.09.5
20305.1 ± 1.412.0
25300.5 ± 2.218.5
50275.0 ± 3.520
Table 3. Weight loss of JEFT/r-HDPE composite samples as a function of burial days.
Table 3. Weight loss of JEFT/r-HDPE composite samples as a function of burial days.
JEFT wt.%Initial Weight (g)Final Weight (g)Weight Loss (%) in 60 Days
01.0961.0940.1
51.1721.1610.9
101.1541.1401.2
151.0931.0781.4
201.0661.0432.1
251.0891.0117.0
501.1901.03113.4
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Alfaifi, H.Y.; Aldress, S.D.; Alshammari, B.A. Exploitation of Plastic and Olive Solid Wastes for Accelerating the Biodegradation Process of Plastic. J. Compos. Sci. 2025, 9, 445. https://doi.org/10.3390/jcs9080445

AMA Style

Alfaifi HY, Aldress SD, Alshammari BA. Exploitation of Plastic and Olive Solid Wastes for Accelerating the Biodegradation Process of Plastic. Journal of Composites Science. 2025; 9(8):445. https://doi.org/10.3390/jcs9080445

Chicago/Turabian Style

Alfaifi, Hassan Y., Sami D. Aldress, and Basheer A. Alshammari. 2025. "Exploitation of Plastic and Olive Solid Wastes for Accelerating the Biodegradation Process of Plastic" Journal of Composites Science 9, no. 8: 445. https://doi.org/10.3390/jcs9080445

APA Style

Alfaifi, H. Y., Aldress, S. D., & Alshammari, B. A. (2025). Exploitation of Plastic and Olive Solid Wastes for Accelerating the Biodegradation Process of Plastic. Journal of Composites Science, 9(8), 445. https://doi.org/10.3390/jcs9080445

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