To successfully handle increasing amounts of plastic packaging waste and meet stricter recycling quotas, innovation will need to occur in European waste management in the coming years. The aim of this paper, written within the project "EsKorte", is to present the state of the art of plastic packaging sorting plants and to describe the resulting potential of sensor-based material flow monitoring. In the first section, the factors influencing the composition and quantity of the plant input are discussed, which subsequently determine the possibilities of plant monitoring and process optimization. Furthermore, the operating principle and influencing parameters of typical aggregates of the plant are described. Finally, some possibilities for the implementation of sensor-based material flow monitoring are presented. The focus of this work is on the situation in Austria, although other European plants and systems are also taken into account for a comprehensive consideration of the topic. The main result of the work is the importance of the positioning of sensor-based monitoring modules in a plant. For example, material flow monitoring directly upstream of the press can provide quality assurance of output fractions, while the same sensor unit at another location in the plant can assess the functioning of individual aggregates. This work thus represents the thematic basis of the research work in the "EsKorte" project, in which basic research-oriented investigations are being carried out for the development and testing of a sensor-based material flow monitoring system for plastic packaging sorting plants.