A novel manometric test to assess inherent biodegradability of complex and non-soluble chemicals

This study presents a modified manometric test for inherent biodegradability designed to assess the inherent biodegradability of complex and poorly soluble chemicals, including polymers with adsorption behavior. The method is derived from OECD 301F and adjusted toward inherent conditions, with higher biomass loading and an optimized Mass/ Food ratio. It addresses limitations of traditional tests, particularly for polymers and substances with low solubility or adsorption properties, while offering enhanced automation. The study used chemicals such as sodium benzoate and polyhydroxybutyrate to assess the modified manometric test for inherent biodegradability using OxiTop®-IDS pressure sensors, comparing it against standard OECD 301F (manometric pressure) and OECD 302B (DOC removal). The modified manometric test for inherent biodegradability enabled the assessment of biodegradability for pure chemicals and of overall biodegradability for complex polymers. Reference soluble chemicals that were evaluated achieved biodegradation levels between 78 and 100%. For polymers, the method overcame solubility and adsorption challenges, with biodegradation levels ranging from 76 to 100% for biodegradable polymers. Notably, in the BMT-C* polymer case study, OECD 302B indicated high apparent biodegradation based on DOC removal, whereas the modified manometric test for inherent biodegradability showed substantially lower biodegradation, highlighting the potential of DOC-based methods to overestimate biodegradation in such systems. These results support the potential of the method as an interesting option for determining overall inherent biodegradability of complex polymers. Significance: The modified manometric test for inherent biodegradability extends inherent biodegradability testing to low-solubility and adsorptive substances while maintaining agreement of 301F/302B results for soluble references (78-100% in 28 d).