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.

Biopolymers and bio-based plastics, such as polylactic acid (PLA) and polybutylene succinate (PBS), are recognized as environmentally friendly materials and are widely used, especially in the packaging industry. The purpose of this study was to assess the degradation of PLA- and PBS-based formulations in the forms of granules and films under controlled composting conditions at a laboratory scale. Biodegradation tests of bio-based materials were conducted under controlled aerobic conditions, following the standard EVS-EN ISO 14855-1:2012. Scanning electron microscopy (SEM) was performed using a high-resolution Zeiss Ultra 55 scanning electron microscope to analyze the samples. After the six-month laboratory-scale composting experiment, it was observed that the PLA-based materials degraded by 47.46–98.34%, while the PBS-based materials exhibited a final degradation degree of 34.15–80.36%. Additionally, the PLA-based compounds displayed a variable total organic carbon (TOC) content ranging from 38% to 56%. In contrast, the PBS-based compounds exhibited a more consistent TOC content, with a narrow range from 53% to 54%. These findings demonstrate that bioplastics can contribute to reducing plastic waste through controlled composting, but their degradation efficiency depends on the material composition and environmental conditions. Future efforts should optimize bioplastic formulations and composting systems while developing supportive policies for wider adoption.