This paper assesses the environmental loads of polypropylene and PP-PE-PET mixed-plastic products throughout the products' life cycle in the production stage, with particular focus on the looping method. A life cycle model of homogeneous and mixed-plastic products has been developed from the raw material extraction and production phase through its transport with the help of the life cycle assessment method. To find the answers to the questions posed, different impacts were analyzed by the GaBi 9.5 software. The analysis lasted from the beginning of the production process to the end. The aim of this research was to determine the energy and material resources used, the emissions produced, and the environmental impact indicators involved. This article examines three scenarios in the production stage, based on the usage of plastic scrap and process water: (1) plastic scrap and wastewater are recirculated with looping method; (2) plastic scrap goes through an incineration process and wastewater is treated in a municipal wastewater treatment plant; (3) plastic scrap is sent to a municipal landfill and wastewater is treated. This article tries to answer three questions: (1) how can we optimize the production stage? (2) Which materials and streams are recyclable in the design of the life cycle assessment? (3) What is the relationship between the environmental impacts of homogeneous and mixed-plastic products? The results of this research can be used to develop injection-molding processes with lower environmental impacts and lower releases of emissions.
Keywords: life cycle assessment; mixed-plastic product; polypropylene product; production life cycle stage.