Introduction Biodegradable polymers are an important part of the solution toolbox to achieve a circular economy and fall into two classes: a.) Structural biodegradable polymers applied as soil biodegradable mulch film or compostable bags and for selected packaging applications. b.) Water-Soluble Polymers (WSP`s) are applied in home and personal care and agro applications. Biodegradable polymers need to excel a technical performance level in the application to fulfill their function during the use phase and a biodegradation performance level after use. This presentation addresses key aspects of polymer biodegradation in both natural and engineered systems following a more holistic approach (“Biodegradability 2.0”) and thereby provide guidance for developing, testing, and regulating biodegradable polymers. These aspects include definitions of biodegradability and biodegradation, elucidating polymer- and environmental factors that control the biodegradation process, a discussion of the analytical chemistry and microbiology of polymer biodegradation, polymer biodegradability testing & certification, development of new polymers and digital tools like predictive biodegradation modelling, respectively. Structural polymers as role model for the investigation of polymer biodegradation Different technologies have been developed over the past years together with our cooperation partners to elucidate the fate of polymeric materials in soil. 13C-labelling combined with different analytical techniques allowed to quantitatively track the polymeric material during the biodegradation process and to close the mass balance . For the first time ever, evidence was provided that carbon from synthetic biodegradable polymers is incorporated in the active biomass of microorganisms during the biodegradation process . Microorganisms and enzymes from different soils have been identified, as well as their communities, and it has been proven that a broad variety of fungi and bacteria are involved in the biodegradation process. Biodegradation of Water-Soluble Polymers (WSP`s): key considerations, status and path forward Thanks to their unique properties, water-soluble polymers (WSPs) find application in many products, such as home and personal care or agricultural formulations . For applications resulting in the release of WSPs into natural environments (e.g. agricultural soils) or engineered systems (e.g. wastewater treatment plants), biodegradable WSPs have the advantage that they are metabolized by microorganisms and, thereby, to be converted under aerobic conditions into carbon dioxide, and biomass. In this presentation, we show, how the gained know how of biodegradation for structural biodegradable polymers can be adapted and transferred to WSP`s. A deep understanding of the environmental fate of WSP`s can only be achieved with a holistic approach to the topic, from the chemical structure to the test methods, from the environmental factors to the biology (microbes, enzymes) (figure 1). Testing of the biodegradation of WSP`s in laboratory can build on the existing test methods developed for small molecules (e.g. OECD 301 B and F) whereas adaptation is needed, due to the different nature of the materials under investigation. In addition, 13C-labelling and microbial enrichments can provide valuable insight into the biodegradation processes. Recent results will be presented including a proposal for biodegradation testing schemes for WSP’s.