Organic Municipal Waste—Testing and Analysis of End Products for Use in the Circular Economy and Their Potential Implications for Climate Change Mitigation

Municipal organic waste is one of the types of waste generated mainly in households but also by other producers. The key to managing this waste is to use appropriate treatment processes to reduce its negative impacts on the environment. The composting process involves the decomposition of persistent organic pollutants and their binding with the organic fraction. This study involved quantitative and qualitative research and analyses of organic waste contained in mixed municipal waste and selectively collected waste in Poland between 2020 and 2024. The aim of the study was to compare the final parameters of two types of organic waste after biological treatment, assess their potential management pathways within the circular economy, and discuss their potential relevance to greenhouse gas mitigation. The research results showed that, after applying the same biological processes to the two analyzed organic waste streams, the final products exhibited significant differences in physicochemical parameters, which necessitates the use of different management methods. The first end product can be classified as compost—a potential fertilizer—and must meet quality requirements for an organic soil improver. The second end product can be used for land reclamation if it meets all three criteria: an AT4 (four-day aerobic respiration activity of the material) value of <10 mgO2/g dry weight, loss on ignition of less than 35%, and organic carbon content of less than 20% dry weight. The products of the biological treatment of organic waste include fertilizers and stabilized waste intended for further processing.