Evaluating Laboratory Methods for Biodegradability Testing: Liquid vs. Solid Phase in Composting Conditions for Textile and Leather Materials

The circular economy emphasizes reducing raw material use and promoting material recycling, with composting serving as an effective method for organic recycling. The European standard EN 13432:2000 provides guidelines for composting-based recovery of packaging materials, primarily through biodegradability tests in a solid phase that simulate composting conditions. Additionally, it includes a liquid phase test as an alternative for certain materials. This study aims to evaluate the suitability of the liquid phase method for industrial use, particularly for screening material biodegradability during the development process of compostable products. By using the simpler liquid phase test to prioritize samples, researchers can identify those that are worth further evaluation through the solid phase method, which more closely mirrors real composting conditions. A key innovation in this research is the evaluation of biodegradability in solid and liquid phases to assess the compostability of diverse materials beyond plastics and packaging. The study assessed 26 materials using both methods, finding a statistically significant correlation (R2 = 0.89) between the results. This strong relationship suggests that the liquid phase method can serve as a reliable estimator for solid phase biodegradability, offering industries a faster and more cost-effective tool for initial material assessments. These findings highlight the potential of integrating liquid phase methods into the material development process, while maintaining the reliability required for compostability standards.