A research team has mapped how wastewater, so far an overlooked source of potassium fertilizer, offers a potential alternative to conventional potash mining. Potassium is indispensable for crop growth, yet fertilizer production depends heavily on mineral deposits concentrated in a few countries. By examining 110 publications, the researchers identified promising ways to recover this nutrient from human urine, livestock waste, industrial effluents, and municipal treatment streams. Their findings show that no single recovery method suits every source: concentrated wastewater favors solid, multi-nutrient fertilizers, while more dilute streams may be better suited to liquid products. The review offers a practical roadmap for turning nutrient losses into agricultural resources.
Farmers rely on potassium to support plant growth, water regulation, and crop resilience. Today, most agricultural potassium comes from mined potash, whose extraction can generate saline waste and damage freshwater ecosystems. Concentrated global supply also exposes fertilizer markets to geopolitical and economic disruption. Wastewater contains recoverable potassium, but wastewater treatment plants typically prioritize nitrogen and phosphorus, leaving much of this nutrient unused. Previous studies have tested precipitation, membranes, and selective separation, yet their findings remain scattered across different waste streams and experimental conditions. Many experiments use artificial solutions rather than the complex mixtures handled by wastewater treatment plants. Given these challenges, a deeper investigation is needed into which wastewater sources, recovery technologies, and fertilizer products can work together in practice.
Researchers Cora Eichholz and Heidrun Steinmetz from the Department of Resource-Efficient Wastewater Treatment at RPTU Kaiserslautern-Landau in Germany report (DOI: 10.1016/j.ese.2026.100777) their findings in Environmental Science and Ecotechnology in a paper accepted on October 8, 2026. Examining 110 publications, the review connects potassium concentrations, recovery processes, product forms, and barriers to practical deployment, showing why wastewater composition should guide fertilizer design rather than treating all nutrient-rich effluents as interchangeable sources.
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