Microplastics in Biosolids: Integrating Environmental Risk Assessment into Sustainability Engineering Education

The land application of biosolids derived from wastewater treatment plants is widely practiced as a nutrient recycling strategy in agricultural systems. However, increasing evidence demonstrates that biosolids contain emerging contaminants, including microplastics (MPs), which may pose ecological and human health risks. Although wastewater treatment effectively removes a substantial fraction of MPs from influent, these particles accumulate in sewage sludge and are subsequently introduced into agricultural soils through land application. Despite growing documentation of their occurrence, fate, and potential impacts, comprehensive environmental risk assessment (ERA) frameworks remain insufficiently integrated into biosolids management and agricultural sustainability evaluation. This opinion paper advances two central arguments. First, it synthesizes existing literature to evaluate a conceptual ERA framework for biosolid-borne MPs, structured around hazard identification, exposure assessment, toxicity assessment, and risk characterization. Second, it argues that sustainability engineering education must embed emerging contaminant risk frameworks into curricula to prepare graduates capable of addressing plastic pollution challenges within agricultural and circular economy systems. A newly developed curriculum incorporating problem-based learning (PBL), minute papers, and a gamified ERA-based group project is presented as a replicable educational model. Linking ERA research with curriculum innovation is essential for developing employment-ready professionals equipped to mitigate plastic pollution and its climate implications.