Transforming percolated urine into safe fertilizer: tracking pharmaceutical and nutrient dynamics

Human urine is a valuable nutrient source that can substantially contribute to agricultural nitrogen supply when converted into safe fertilizer products. In Germany, larger urine volumes are mainly collected with mobile event toilets using serial urine diversion, where urine percolates through solid human excreta mixed with bulking material. In a living lab, 6 m 3 of stored percolated urine (“percurine”) were treated by pilot-scale nitrification, activated carbon filtration, and evaporation. The study examined how percolation affects matrix composition relative to urine directly diverted in the toilet bowl and whether the treatment train reduces expected microbiological and chemical contaminants. Starting material, intermediate products, and final products were analyzed for nutrient composition, hygienic parameters, heavy metals, pharmaceutical residues, and organic pollutants. Stored percurine showed 325 CFU mL −1 Enterococcus spp., below the DIN SPEC 91421 (2020) threshold, with further reduction during processing. Because of urine’s physicochemical properties, adaptation and matrix-specific validation of standard methods will likely be needed for reliable detection of somatic coliphages and Clostridium perfringens . Of 100 pharmaceutically active substances, 15 were detected above the limit of quantification in the concentrated product, with a cumulative concentration below 18 μg L −1 ; phenazone, nicotine, ciprofloxacin, and ofloxacin were most relevant. Compared with literature values for stored urine, nitrogen (2,190 ± 340 mg L −1 ) and phosphorus (135 ± 22 mg L −1 ) were 47% and 44% lower, respectively. Normalizing macronutrients to chloride suggests approximate losses of 10% N, 20% P, and 10% K during processing. TOC in PUR was 700 ± 340 mg L −1 , clearly lower than typical urine values. Despite its altered composition, nitrified, filtered, and evaporated percurine could qualify as an organic or organo-mineral fertilizer under the German Fertilizer Ordinance (DüMV), provided human excreta were recognized as a material category. However, it differs substantially from marketed products such as Aurin in composition and nutrient density, which may affect agronomic potential.