Case studies that show the predictive modelling of microplastic accumulation in the natural environment

The use of plastics inevitably leads to (micro-)plastics entering and accumulating in the natural environment, affecting biodiversity, food security and human health. Biodegradable polymers have emerged as a potential solution to mitigate plastic pollution and the environmental accumulation of polymers, offering stable performance during use while leading to shorter residence times in natural environments. But do we know the effect of these novel polymers on microplastic accumulation in the natural environment? We developed a comprehensive and universally applicable method to quantify microplastic accumulation in the natural environment. This method includes an integrated biodegradation model that provides the possibility to examine and compare the microplastic formation and accumulation of different polymer types in diverse natural environments. The model uses experimental mineralisation curves of polymers to predict the microplastics accumulation. The model fits the mineralisation curves to a state-space model and therewith generates a mass balance of substances formed during the biodegradation process. This polymer-environment specific mass balance is used to predict the concentrations and residence times of microplastics in the natural environment. The modelling results can be used directly to assess and compare the accumulation of different polymers, and could be used as input for sustainability studies such as a life cycle analysis (LCA). Ultimately, the proposed methodology identifies the required biodegradation behaviour to prevent the microplastic accumulation of specific plastic products in the natural environment. This will facilitate the transition to a system in which products are designed based on their intended functionality and anticipated end-of-life scenario. For this presentation, the model is applied in different case studies to study the possible benefits of the use of biodegradable polymers as a solution to environmental accumulation of polymers. These case studies are focused on different applications of biodegradable polymers, in different environments. The preliminary results of modelled case studies show that replacing non-biodegradable polymers with biodegradable polymers can be effective in the prevention of environmental microplastic accumulation, even in case of higher littering ratios or the application in agricultural products that are not retrieved from the land.