Microplastic Analysis on Microbial Compost, Vermicompost, and Superworm Compost and Their Ecological Risk Assessment

Abstract Microplastic pollution in organic compost products raises concerns for environmental safety and agricultural soil quality. This study aims to identify the presence, characteristics, and ecological risk level of microplastics in three types of commercial compost, namely microbial compost (MO), vermicompost, and superworm (SW) compost. The research was conducted experimentally by sampling compost from three producers, followed by the microplastic extraction process using the ZnCl 2 solution density flotation method and H 2 O 2 oxidation methods. Identification of morphology, color, and size was performed using a stereo microscope, while the type of polymer was confirmed through FTIR spectroscopy. The data were analyzed descriptively, quantitatively, and using ecological risk assessment. The results showed that MO had the highest number of microplastics (64 particles/kg), followed by vermicompost (33 particles/kg), and SW (19 particles/kg), with the predominance of fragment forms and polyethylene (PE) polymers. The ecological risk index values are 704 (MO), 330 (vermicompost), and 209 (SW), respectively, all of which fall into the high‐risk category (Level IV), but decrease as biological activity in the composting process increases. It is concluded that the intensity of biological degradation plays an important role in reducing the content and risk of microplastics in organic compost. These findings confirm the importance of developing a composting system based on soil biota as a natural mitigation strategy to reduce microplastic contamination in the agricultural environment.