Waste to resource: A review of nitrate and phosphate removal from agricultural runoff using recycled byproducts

Agricultural runoff carries excessive loads of nitrates and phosphates that degrade water quality and disrupt surrounding ecosystems. Conventional approaches, such as best management practices for fertilizer application and runoff collection, can mitigate nutrient losses, yet their effectiveness is limited and often insufficient to address large-scale nutrient pollution. More advanced technologies, including reverse osmosis and activated carbon adsorption, provide high removal efficiency but remain costly and energy-intensive, restricting their widespread adoption. As a sustainable alternative, waste valorization has gained attention for utilizing non-hazardous industrial byproducts (e.g., fly ash, casting sands) and agricultural residues (e.g., rice husk, sugarcane bagasse) as low-cost biosorbents to capture nutrients directly at the source. This review evaluates the performance of recycled byproducts tested for nitrate and phosphate removal, analyzes the chemical and microbial mechanisms underlying nutrient adsorption and denitrification, and assesses the economic feasibility and scalability of these materials. Furthermore, research trends, innovations, and knowledge gaps are identified, with emphasis on field-scale validation to optimize longevity and minimize unintended environmental consequences. By advancing waste-derived biosorbents as viable nutrient management tools, this review highlights their potential to enhance water quality, promote circular economy practices, and inform future research and policy development in sustainable agriculture. • Waste valorization comes from a wide range of industrial and agricultural sources. • Biosorbent material can provide increased adsorption of nutrients (nitrogen and phosphorus) in runoff. • Chemical functionality and characterization play a critical role in adsorption of analytes to waste materials. • Economic feasibility will drive the beneficial use of waste as biosorbent material. • Chemical modification to waste materials can be made to increase adsorption but increase overall cost.