Degradation and Disintegration Behavior of PHBV- and PLA-Based Films Under Composting Conditions

Abstract

This study investigated the degradation and disintegration behavior of novel biobased multilayered films composed of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) during controlled composting tests performed at the laboratory scale. The compostability of monolayer PLA and PHBV films, hot-pressed bilayers, and coextruded multilayer films produced in industrial or semi-industrial settings was systematically evaluated. Materials supplied by Fraunhofer LBF (Darmstadt, Germany) were tested as specified by the EVS-EN standard ISO 14855-1:2012 and EVS-EN ISO 20200:2016 standards. Composting took place in sealed, aerated vessels at 58 ± 2 °C with 50 ± 5% moisture and >6% oxygen. Biodegradation was measured via CO₂ evolution, and disintegration was assessed visually and physically. PLA-1OLA films achieved 98.59% biodegradation and 91.13% disintegration. PHBV-5OLA and multilayer PLA-1OLA/PHBV-5OLA films showed biodegradation rates of 85.49% and 73.14%, with disintegration degrees of 89.93% and 79.18%, respectively. However, modified multilayer structures displayed slightly reduced compostability compared with pure compounds, likely due to the influence of additional components. To meet the 90% biodegradability threshold required by EVS-EN 13432:2003, increasing the PLA-1OLA content is recommended. This study introduces a novel combination of biobased polymers and plasticizers in multilayer formats, offering a deeper understanding of structure–property–degradation relationships. Its significance lies in advancing the design of sustainable packaging materials that balance functionality with environmental compatibility.

1. Introduction

Plastics have become ubiquitous pollutants in many environments [1,2,3]. Over the last five decades, plastic manufacturing has expanded nearly twentyfold. Worldwide, it is estimated that about 9200 million metric tonnes (Mt) of plastics have been produced, of which more than 6900 Mt have ended up in landfills or have leaked into the environment. In 2019, the global output was 368 million Mt, and current projections indicate that this figure may double within the next two decades [4]. The rising trend in plastic production and consumption is driven by ongoing societal and economic shifts [5,6].

Most plastics are derived from petroleum and exhibit limited environmental biodegradability. This lack of biodegradability leads to their accumulation in landfills, posing a significant threat impacting ecosystems in both land and ocean environments (for example, see Figure 1) [6]. Landfilling is not entirely phased out in Europe and is still common in many global regions [7].

The depletion of petroleum resources and the environmental challenges posed by plastic waste have stimulated significant interest in developing polymers of renewable origin that are both bio-based and biodegradable [8,9]. One of the major research priorities involves creating compostable packaging films with barrier properties that may be discarded together with food waste in cases where recycling is impractical [6]. To address plastic pollution, researchers have explored various post-treatment technologies, including biodegradation [10], in which microorganisms break down organic matter, offering a promising sustainable solution [11,12]. Additionally, the use of biodegradable plastics can help reduce greenhouse gas emissions during their lifecycle [13].

Biodegradable plastics show highly variable degradation rates across environments, which in some cases can result in the accumulation of chemical byproducts and intermediate compounds [8]. When favorable conditions are present—adequate moisture, oxygen availability, and active microbial communities—these plastics may mineralize to carbon dioxide (CO₂) and water (H₂O) within a period of 20–45 days, as observed in natural landfills or manure systems. In contrast, conventional plastics remain intact for centuries or even millennia [11,13].

Various types of enzymes play an important role in the degradation of plastic polymers. Currently, microbial enzymes are considered a potential resource for converting plastic polymers into monomers [11,13]. In recent years, extensive research efforts have focused on identifying microorganisms and enzymes with plastic-degrading abilities [14,15,16]. The search for novel plastic-degrading microbial strains and enzymes is ongoing and holds great promise for improving the feasibility of biodegradation as a strategy to address the accumulation of plastic waste. Moreover, the development of processes that not only degrade but also convert plastic waste into higher-value products is viewed as a crucial step toward mitigating plastic pollution in a sustainable manner [17].

As a result, several testing methods are available to assess biodegradability in various environments [17,18]. Plastic biodegradation is typically assessed by measuring the conversion of organic carbon into CO₂ within sealed laboratory systems under controlled conditions. Several standardized methods, including ISO 13432 [19], ISO 14855-1 [20], ISO 14855-2 [21], and ISO 17556 [22], have been developed to evaluate whether materials meet established biodegradability criteria in soil or compost environments. The main factors influencing degradation in such settings are temperature, moisture availability, and the presence of microorganisms capable of polymer breakdown. Because these parameters vary with climate, soil characteristics, and management practices, a material that achieves complete degradation in one context may fail to do so in another [23].

Degradation in controlled composting conditions entails placing the material in a stationary composting vessel devoid of light, where it is actively aerated under optimal conditions of 50 ± 5% moisture, oxygen levels above 6%, a temperature maintained at 58 ± 2 °C, and pH values between 7.0 and 9.0 [20,24].

Biobased and biodegradable polymers, including poly(lactic acid) (PLA) and polyhydroxyalkanoate (PHA), are promising alternatives to conventional polymers in specific applications, particularly for non-durable goods and single-use products [9,25].

PLA-based biodegradable polymers are commonly used in the packaging industry because of their unique mechanical and physical properties, their renewable origin, and their ability to have active properties such as antimicrobial and antioxidant effects. Nevertheless, their barrier properties need improvement if they are to be used satisfactorily in certain applications [26,27]. PLA requires specific conditions for effective composting, such as higher temperatures typically found in industrial composting facilities. The degradation of PLA is slower under natural environmental conditions [28,29,30].

Laboratory-scale composting experiments conducted by Wend et al. revealed that PHBV-based films are biodegradable, with the degree of fragmentation influenced by composting parameters and hydroxyvalerate (HV) content [8]. Because of its microbial derivation and enhanced degradability, PHBV can also break down more readily in natural environments such as soil and marine ecosystems [31,32].

Films composed of a single layer frequently do not achieve the balance between cost-effectiveness and the required material performance. In response, multilayer films are developed to fulfill the design specifications of various applications, including the food industry and agriculture. These films integrate the diverse properties of various materials to achieve one or more objectives, including improved performance, cost reduction, and streamlined processing [33].

While many investigations have explored the degradation characteristics of biodegradable polymer blends, this study offers several unique and noteworthy advancements. One study examined PLA/PBS/PBAT blends processed via melt mixing, yet focused solely on physical and chemical properties without evaluating biodegradation or disintegration directly [34]. Other studies investigated PLA/PCL/MCC blends using similar biodegradation tests but incorporated microcrystalline cellulose (MCC) and polycaprolactone (PCL), which are known to enhance degradation rates, thus differing regarding composition and performance expectations [35]. Some investigations addressed PLA blends under anaerobic digestion conditions or explored their behavior without evaluating disintegration or biodegradation [36,37]. Similarly, research on PHBV and its blends, either as standalone materials [38] or combined with PPC through solution blending [39], emphasized in vitro degradation or soil suspension tests rather than standardized composting methods. Additional studies focused on PHBV degradation in soil without examining the disintegration process [40].

Unlike previous studies, this research focused on PLA- and PHBV-based formulations as primary materials, with the addition of OLA, assessed in composting environments compliant with ISO 14855-1:2012 [20] and ISO 20200:2016 [41] to gain deeper insights into their degradation and disintegration pathways. This study also considered the EU legal framework for compostable plastics, including Directive (EU) 2019/904 concerning Single-Use Plastics and the provisions set forth in the Packaging and Packaging Waste Regulation (2025/40) [42,43]. In addition, the EN 13432:2003 [19] standard was referenced to define the biodegradation and disintegration criteria [19]. Coextruded monolayer and hot-pressed bilayer films, produced in industrial or semi-industrial settings, were used as test materials. Biodegradation was monitored over six months at the laboratory scale using titration to determine cumulative CO₂ evolution and directly quantify the degree of biodegradation, while disintegration tests were conducted over three months, following EVS-EN ISO 20200:2016, by quantifying the remaining polymer mass. Structural changes before and after composting were also analyzed using scanning electron microscopy (SEM), providing further insight into surface-level degradation over time.

2. Materials and Methods

2.1. Materials

Tests of biodegradation and disintegration were carried out on multilayer films composed of PLA and PHBV, developed for packaging purposes. The film materials were obtained from the Technical University of Madrid (UPM, Madrid, Spain) and Fraunhofer Institute for Structural Durability and System Reliability LBF (Fraunhofer LBF, Darmstadt, Germany).

PLA-1OLA and PHBV-5OLA monolayer films were produced via co-extrusion under industrial or semi-industrial conditions as described by Vírseda et al. In contrast, the bilayer PLA-1OLA/PHBV-5OLA film was fabricated via compression molding. The influence of processing parameters—temperature, pressure, pressing time, and cooling rate—on the bilayer quality was evaluated. The optimal conditions were identified as 150 °C, 100 bar, a pressing time of 1 min, and rapid cooling [44]. The required pre-assessments of the samples were performed according to the guidelines specified in EVS-EN ISO 14855-1 [20], which defines the determination of ultimate aerobic biodegradability of plastics under controlled composting by analyzing evolved CO₂, and in EVS-EN ISO 20200:2016 [41], which outlines the determination of the degree of disintegration of plastics under simulated laboratory-scale composting conditions.

Table 1. The materials tested for compostability, and their properties.

Polymer Type	Composition	Sample Name	Film Thickness (mm)	TDS (%)	TVS (%)	TOC (%)
Monolayer	PLA 99% + 1% OLA	PLA-1OLA	0.5 mm	99.86	>99.9	50
	PHBV 95% + 5% OLA	PHBV-5OLA	0.25 mm	99.19	>99.9	58
Bilayer	99 w% PLA + 1 w% OLA // 95 w% PHBV + 5 w% OLA	PLA-1OLA/PHBV-5OLA	0.35 mm	99.41	>99.9	54

provides details on the tested materials and their properties.

2.2. Methods

2.2.1. Composting at Laboratory Scale

Biobased multilayer samples (20 × 20 mm) were subjected to biodegradation testing under controlled aerobic composting conditions following EVS-EN ISO 14855-1:2012 [20]. As prescribed in the standard, the plastics were mixed with activated vermiculite inoculum in a 1:4 dry mass ratio and incubated in stationary vessels aerated with CO₂-free air. Optimal conditions were maintained for six months: moisture 50 ± 5%, oxygen > 6%, temperature 58 ± 2 °C, and pH between 7.0 and 9.0. The design included triplicate vessels for blanks (inoculum only), controls (TLC-grade cellulose < 20 μm), and each test material. The experimental setup is schematically illustrated in Figure 2.

In all composting vessels, carbon dioxide release was tracked continuously and recorded at regular time points. CO₂ release from vessels containing test material plus inoculum was compared with that from blank vessels containing only inoculum. Weekly operations involved moisture adjustment, vessel shaking, and pH assessment to maintain stable composting condition.

For each sample, the theoretical CO₂ release (ThCO₂) was calculated as a function of the total dry solids (M_TOT), the total organic carbon (C_TOT), the molecular weight of CO₂ (44), and the atomic weight of carbon (12), as defined in Equation (1):

$${\mathrm{T}\mathrm{h}\mathrm{C}\mathrm{O}}_2={\mathrm{M}}_{\mathrm{T}\mathrm{O}\mathrm{T}}·{\mathrm{C}}_{\mathrm{T}\mathrm{O}\mathrm{T}}·{\displaystyle \frac{44}{12}}$$

(1)

The titration procedure according to EVS-EN ISO 19679:2020 [45], was used to evaluate the carbon dioxide produced throughout the test by the blank vessels (CO₂)_B and vessels with the test materials (CO₂)_T, measured in grams per vessel. This method enabled a calculation of the percentage of material biodegradation (D_t) using Equation (2):

$${\mathrm{D}}_{\mathrm{t}}={\displaystyle \frac{{\left({\mathrm{C}\mathrm{O}}_2\right)}_{\mathrm{T}}-{\left({\mathrm{C}\mathrm{O}}_2\right)}_{\mathrm{B}}}{{\mathrm{T}\mathrm{h}\mathrm{C}\mathrm{O}}_2}}·100\mathrm{\%}$$

(2)

2.2.2. Disintegration at Laboratory Scale

Disintegration tests were conducted on biobased multilayer films (25 × 25 mm) in accordance with EVS-EN ISO 20200:2016 [41]. Test specimens (5 g) were mixed with 350 g of wet synthetic waste and incubated in stationary composting vessels under dark, thermophilic conditions (58 ± 2 °C) for 90 days with continuous aeration. To maintain the desired compost moisture, water was periodically added—initially adjusted to 80% and subsequently reduced to 70% of the starting mass. The compost mixture was stirred at regular intervals to ensure uniform aeration and humidity. The setup of the experiment is depicted schematically in Figure 3.

After the test, the compost collected from each reactor was subjected to sieving using a sequence of sieves with mesh sizes of 10, 5, and 2 mm. Lumps of compost were gently broken apart during the sieving process. The test material retained at each sieving stage was pooled, cleaned of compost residues, and washed by dipping it in water.

For each reactor, the extent of disintegration was determined by normalizing the measured sample weights at successive time points against their original values. According to Equation (3), the degree of disintegration (D) corresponds to the relationship between the initial dry mass (mᵢ) and the remaining dry mass (mᵣ) of the material. Photographs of the samples were taken at regular intervals to document the progression of disintegration.

$$\mathrm{D}={\displaystyle \frac{{\mathrm{m}}_{\mathrm{i}}-{\mathrm{m}}_{\mathrm{r}}}{{\mathrm{m}}_{\mathrm{i}}}}·100$$

(3)

2.2.3. SEM Characterization

SEM analysis of the samples was performed with a Zeiss Ultra 55 high-resolution microscope (Jena, Germany). The instrument operated at 15 kV, and images were acquired using SE2 (secondary electron) and AsB (back-scattered electron) detectors.

2.2.4. TOC Analysis

TOC content in the investigated polymers was measured using a Vario TOC Solids Module (950 °C, Elementar GmbH, Langenselbold, Germany) according to EVS-EN ISO 14855-1. As prescribed by ISO 10694:1995 [46], the samples were heated to 950 °C under an oxygen-rich, CO₂-free gas flow, which enabled full decomposition and oxidation of the sample carbon to carbon dioxide (CO₂). The generated CO₂ was then recorded by the instrument.

3. Results and Discussion

3.1. Biodegradation Tests

Throughout the experimental period, the degradation rate of the control, the plateau stage, and soil pH were monitored. TLC-grade cellulose reached its plateau on day 110 with a maximum average degradation of 97.19%. The test was validated, as the reference material exceeded the 70% biodegradation threshold within 45 days [47]. During the study, the pH of the activated vermiculite remained consistently within the range of 7.0–9.0.

The PLA- and PHBV-based films showed variations in TOC content: PLA-1OLA contained 50%, PHBV-5OLA 58%, and the bilayer (PLA-1OLA/PHBV-5OLA) demonstrated an intermediate value of 54% (Table 1). The cumulative CO₂ release (g/g) of biobased compounds over six months of controlled composting is shown in Figure 4, while Figure 5 presents their biodegradation levels over the same period.

3.1.1. PLA-Based Monolayer Film

A PLA-1OLA sample with a thickness of 0.5 mm produced an average of 1.8 g/g of CO₂ and reached a biodegradation rate of 98.59%, demonstrating substantial biodegradability under controlled composting conditions. By day 130 of composting, the biodegradation degree surpassed 90%, in agreement with Kalita et al., who observed 94.2% biodegradation of pure PLA after 136 days [48]. The biodegradation process started slowly after 30 days, compared with other samples. This delay can be explained by the relatively high thickness of PLA-1OLA of 0.5 mm and the additive affecting the process. However, the addition of 1% OLA does not appear to have a significant impact on the decomposition of PLA material under aerobic conditions. A study by Lyshtva et al. on PLA- and PHBV-based samples found that a PLA-based film consisting of 80% biobased materials and under 20% non-degradable constituents, including plasticizers and processing aids, with a thickness of 0.15 mm, produced, on average, 1.15 g/g of CO₂ and achieved a biodegradation degree of 58.39%. These findings suggest that the presence of additives can potentially slow down the biodegradation process [49].

3.1.2. PHBV-Based Monolayer Film

With a thickness of 0.25 mm, PHBV-5OLA produced on average 1.55 g/g of CO₂ and reached a biodegradation rate of 73.14%. In the study conducted by Lyshtva et al. exhibited comparable results for a material comprising 95 w% PHBV and 5 w% HV, achieving a degradation degree of 71.9% [24]. Under laboratory-scale composting conditions, Weng et al. examined the biodegradation characteristics of PHBV films (3% mol HV) and observed a transition from surface erosion to interior degradation in both pilot- and laboratory-scale composting conditions [8]. According to García-Depraect et al., PHBV films generally show rapid biodegradation under composting conditions. For instance, PHBV films were found to biodegrade anaerobically by 81.2% in 77 days and aerobically by 87.4% in 117 days.

3.1.3. PLA- and PHA-Based Bilayer Film

The PLA-1OLA/PHBV-5OLA (thickness 0.35 mm) bilayer composition produced an average of 1.68 g/g of carbon dioxide (CO₂), with a biodegradation rate of 85.49%. These obtained results imply a high level of biodegradation potential under controlled composting conditions. The biodegradation properties of pure PLA and its blends demonstrated a clear relationship between the blend composition and the biodegradation rate, suggesting that optimizing the composition could enhance the biopolymer’s biodegradability [35].

Although crystallinity was not measured in this study, it may have significantly influenced the biodegradation and disintegration behavior of the tested films. The lower biodegradation rates observed for the PHBV-rich and multilayer films may be partly attributed to their higher crystallinity, which acts as a barrier to water diffusion and enzymatic attack, thereby slowing microbial degradation [50,51,52]. Previous studies have shown that amorphous regions are preferentially degraded, while crystalline domains remain more resistant, commonly enhancing the degree of crystallinity during composting as the amorphous phase diminishes [53,54]. This structural evolution can further reduce the degradation rate over time. Therefore, adjusting the OLA content or optimizing processing parameters to reduce crystallinity could enhance the compostability of these blends and bring their performance closer to the EN 13432 requirements. The biodegradation of PLA-1OLA, PHBV-5OLA, and PLA-1OLA/PHBV-5OLA films also demonstrates a correlation with organic carbon content of these materials. Increasing the weight percentage of PLA-1OLA relative to PHBV-5OLA in the composition may lead to a biodegradation degree of up to 90% for PLA-1OLA/PHBV-5OLA blends. These results suggest that blending PLA with specific polymers enables the production of plastics with programmed biodegradation rates and required physical properties [40,55].

Following six months of compostability experiment, fragility was observed in every examined material. The results suggest that the conditions outlined in Section 2.2.1 contributed to increased brittleness and a noticeable reduction in durability. These changes also reflect the disintegration process occurring within the materials. Further details on the disintegration changes can be found in Section 3.2.

3.2. Disintegration Tests

The appearance of the blends collected at successive testing intervals during the 90-day trial under thermophilic conditions is shown in Figure 6. The images depict samples of organic compost material used in the disintegration process, where synthetic waste was mixed with three different multilayer plastic films: PHBV-5OLA, PHBV-5OLA, and PLA-1OLA/PHBV-5OLA. The varying degrees of polymer film disintegration are evident in each sample.

On Day 0, translucent polymer film fragments remained embedded within the inoculum, marking the beginning of the disintegration process. On Day 10, partially disintegrated polymer films were visible, showing fragmentation and interaction with the compost environment, along with a loss of transparency that indicated ongoing breakdown. The breakdown of the polymer matrices caused modifications in their refractive index, primarily due to water absorption and the production of low-molecular-weight species formed during hydrolytic degradation, resulting in a loss of transparency across all samples [26,56]. On Day 25, the compost appeared more uniform and denser, with no clearly visible polymer fragments, suggesting advanced disintegration of the material. On Day 42, further progression of the disintegration process was evident, with signs of the synthetic waste beginning to transform into compost. By Day 57, the composting process had advanced significantly, leaving only minor fragments of the material visible. Finally, on Day 90, the samples exhibited nearly complete disintegration, with only small remnants of the material remaining. These observations demonstrate the progression of disintegration under composting conditions.

For each reactor, the degree of disintegration (D) was calculated by normalizing the sample weight at different time points to its original mass. As presented in Equation (3), this parameter (D) corresponds to the relationship between the initial dry mass (mᵢ) and the remaining dry mass (mᵣ).

The disintegration results shown in Figure 7 highlight the differences in the breakdown rates among the tested materials. For PLA-1OLA with a thickness of 0.5 mm, the level of disintegration was significant, with a mass loss of 91.13% by the end of the 90-day experiment. In the case of PHBV-5OLA (film thickness 0.25 mm), the extent of degradation was slightly lower compared with that for the PLA-based monolayer film, with a mass loss of 89.83%. However, for the blend of these two materials, PLA-1OLA/PHBV-5OLA, with a film thickness of 0.35 mm, the decomposition degree dropped to 79.18%. This significant reduction in disintegration performance for the bilayer PLA-1OLA/PHBV-5OLA film is likely due to the combination of the two films and the increased barrier properties of the blend.

Multilayer biodegradable films often exhibit significantly lower water and oxygen permeability due to their increased thickness, varying layer compositions, and reduced diffusion pathways [6,57,58]. Although barrier properties were not directly measured in this study, this interpretation aligns with the findings of previous research: enhanced barrier resistance in multilayer materials limits moisture permeability and microbial access—two factors essential for biodegradation and disintegration [59,60,61]. These results indicate that the bilayer’s multilayer structure likely made it harder for water and enzymes to reach the material, contributing to its slower disintegration.

Nevertheless, the mass loss rate could potentially be improved by adjusting the PLA-1OLA monolayer film content or by reducing the overall film thickness. According to Tolga et al. (2020), the thickness of PLA blends has a significant impact on mass loss, with results indicating that a 50% reduction in thickness may increase the disintegration rate by up to 40% [62].

According to Arrieta et al., PHB slows PLA disintegration, as pure PLA disintegrates after 28 days, while increased crystallinity in all materials reduces degradation rates by resisting microbial attack, with crystalline PHB further delaying PLA breakdown [63].

3.3. Surface Morphology

SEM images (Figure 8) were captured for samples collected before and after the 6-month biodegradation and 3-month disintegration tests in the compost medium. These images revealed distinct surface structural changes in both polymers, highlighting the macroscopic alterations occurring during the biodegradation process.

The initial PLA-1OLA sample exhibited significant surface deterioration (see Figure 8a), providing clear evidence of its high biodegradation and disintegration rates, measured at 98.59% and 91.13% (see Figure 5 and Figure 7), respectively. This emphasizes the rapid breakdown of the material under the tested conditions.

The second material, PHBV-5OLA, exhibited a biodegradation rate of 74.13% and a degree of disintegration of 89.93% (see Figure 5 and Figure 7). This facilitated the damage that was seen on the surface of the film presented in Figure 8 and extended deeper into the material during both tests.

The third sample, PLA-1OLA/PHBV-5OLA (a combination of PLA-1OLA and PHBV-5OLA) showed an average biodegradation rate of 85.49% (Figure 5) but a lower degree of disintegration of 79.18% (Figure 7). This result, presented in Figure 8c, revealed stratification between the two layers, which can be attributed to the method by which the sample was produced.

4. Conclusions

The composting process plays a crucial role in assessing the environmental impact and sustainability of developed materials. In the context of biodegradation and disintegration, a multilayer film composed of biobased polymers was thoroughly examined herein to evaluate its environmental effects. The films, composed mainly of PLA and PHBV, showed encouraging results when subjected to controlled composting conditions, where temperature, humidity, oxygen levels, and pH were carefully maintained.

Following ISO 14855-1 standards, PLA-1OLA exhibited strong compostability during a six-month test, achieving an average degradation rate of 98.59%. Meanwhile, PLA-1OLA/PHBV-5OLA and PHBV-5OLA showed significant biodegradation potential, with degradation rates of 85.49% and 73.14%, respectively. However, compared with pure PLA and PHBV compounds, modified biobased films exhibited lower biodegradation rates due to the presence of additional components that impeded the process.

Disintegration tests conducted according to ISO 20200:2016 yielded results consistent with the biodegradation findings, with disintegration rates of 91.13% for PLA-1OLA, 89.93% for PHBV-5OLA, and 79.18% for the multilayer film PLA-1OLA/PHBV-5OLA.

To achieve the EN 13432:2003 minimum requirement of at least 90% biodegradation and 90% disintegration within the required timeframes, increasing the PLA-1OLA content in PLA-1OLA/PHBV-5OLA could enhance this material’s compostability performance.

Material composition, thickness, and structural configuration are shown by these findings to be key factors in compostability performance. While all tested films demonstrated promising biodegradation and disintegration under composting conditions, the bilayer exhibited slower disintegration, likely due to reduced moisture and oxygen permeability. This highlights the need for careful design of multilayer bioplastics to balance functional properties with environmental performance.

Future research should aim to optimize the PLA-1OLA/PHBV-5OLA ratio to improve compostability and meet EN 13432:2003 standards. Studies should also investigate the effects of additives, explore alternative biobased polymer combinations, and analyze the degradation mechanisms. Real-world composting scenarios, lifecycle assessments, and industrial-scale testing are essential to validate performance and environmental impact.