Occurrence and Reduction of Emerging Pollutants in the Process of Organic Solid Waste Recycling

Various emerging pollutants have been detected in organic solid waste in recent years, posing a significant threat to the environment and human health due to biotoxicity, environmental persistence, and bioaccumulation. Organic solid waste bioconversion (aerobic composting and anaerobic digestion) is a crucial method for resource utilization and mitigating emerging pollutants. However, there is a lack of systematic summarization and understanding of the characteristics of different emerging pollutants in the bioconversion of organic solid waste and their degradation pathways. Based on a literature review, this paper summarizes the current research status of typical emerging pollutants in the process of organic solid waste resource utilization, including persistent organic pollutants, endocrine disruptors, antibiotics, and microplastics. It analyzes the characteristics of emerging pollutants in different types of organic solid wastes (food waste, municipal sludge, and livestock manure). It also explores the effects of aerobic composting and anaerobic digestion on removing these pollutants and the strategies for improving removal efficiency. Overall, the average concentration of endocrine disruptors in organic solid waste (23158 μg/kg) is higher than that of antibiotics (12418 μg/kg) and persistent organic pollutants (1268 μg/kg), with the average concentration of microplastics being 34 703 particles/kg. Antibiotics, used as antimicrobial agents and growth promoters, are currently the most studied emerging contaminants, primarily concentrated in livestock manure, where their concentrations are also higher. Research on persistent organic pollutants, endocrine disruptors, and microplastics, which are produced by industrial activities and daily human life, is mainly focused on municipal sludge, where their concentrations are also higher. Municipal sludge and livestock manure carrying emerging pollutants may migrate into crops after land application, thereby contaminating food and derived food waste. Currently, there is relatively little research on emerging pollutants in food waste and its treatment. A review of the literature reveals that research on emerging pollutants in the resource utilization process of organic solid waste spans 33 countries. China is the country with the most research on emerging contaminants (accounting for 72%, which may be related to the number of universities), followed by the United States, Poland, Spain, Canada, and Australia. Research on emerging pollutants is predominantly focused on anaerobic digestion, though there are regional differences. For example, regions such as Shanghai, Hunan, and Jiangsu in China, as well as some foreign countries, primarily focus on anaerobic digestion, while regions like Heilongjiang, Henan, and Guangdong in China mainly focus on aerobic composting. The bioconversion of organic solid waste can effectively control and reduce emerging pollutants in organic solid waste, with aerobic composting generally showing higher capabilities for removing emerging pollutants compared to anaerobic digestion. Finally, further research directions regarding emerging pollutants in organic solid waste resource utilization are discussed to guide subsequent work.