Performance of a modified screening method for polymer biodegradability testing

Because the implementation of the Commission Regulation (EU) 2023/2055, the degradability of products containing microplastic has to be determined before their application in the environment. Therefore, it is important to focus product development towards obtaining biodegradable products which requires appropriate test methods. We developed a modified screening method to facilitate quick biodegradability assessment of polymers and polymeric products. The method is based on the OECD technical guideline (TG) 301. Water-soluble polymers (sodium alginate, gum arabic, carboxymethyl cellulose) were directly tested whereas water-insoluble polymers (Indian psyllium husks) were filtered beforehand and the filter was analysed. Sewage sludge was used to provide a microbial community for the aerobic degradation process. The test system volumes were reduced (50 instead of 800 or 162 mL) and the duration was shortened (10 instead of 28 days incubation time). The modified screening method uses the total organic carbon recovery as an assessment endpoint instead of carbon dioxide (CO2) evolution or oxygen consumption. The performance of the new screening method was comparable to that of OECD TG 301B (standardised test for mineralisation in sewage sludge) for all four polymers when extrapolated to the TG 301 duration, whereas those for TG 301F were lower. For product development the developed modified screening method is a useful alternative due to a shorter incubation time, a simplified set-up and enabling a higher sample throughput.