Beyond the guidelines: rethinking OECD biodegradability testing for polymers in liquid formulations

Abstract

The environmental persistence of polymers in liquid formulations (PLFs) can present a significant challenge for sustainability, particularly given their widespread use and limited post-use recovery. Testing methodologies to evaluate and understand the end-of-life fate of PLFs are therefore essential. This perspective critically evaluates the existing biodegradability testing methods, with a focus on protocols from the Organisation for Economic Co-operation and Development (OECD) which are widely adopted as the gold standard. These methods were originally designed for simple, low molecular weight substances, and we explore their limitations when applied to complex PLFs, such as solubility contraints, structural complexities and alignment of test conditions with realistic environmental fates. The paper explores scientific and regulatory innovations aimed at addressing these limitations, including enhanced microbial characterisation, alternative degradation endpoints, improved simulation environments, and high-throughput screening tools. It also highlights Croda's contributions to advancing biodegradability testing through collaborative research and accelerated testing methodologies. By identifying knowledge gaps and proposing targeted improvements, this work supports the development of more robust, representative, and sustainable testing strategies for modern polymer systems.