The sanitation and urban agriculture nexus: urine collection and application as fertilizer in São Paulo, Brazil

Separately collected urine is an attractive potential fertilizer because of its high nutrient content, low cost, and inherent linkage of urban wastewater management and peri-urban agriculture. Urine from waterless urinals was applied to corn and lettuce plants to examine the impact of urine application rates and frequency on plant growth and soil parameters. In both corn and lettuce experiments, urine application significantly (p < 0.05) increased growth and leaf production relative to control plants. More frequent applications led to lower soil cation exchange capacities for corn and higher soil nitrogen content for both crops. Based on preliminary implementation calculations, waterless urinals at the University of São Paulo (USP), School of Arts, Sciences, and Humanities campus could lead to over 1,500 m³ of water saved and 360 m³ of urine produced on an annual basis. These experiments and modeling results are discussed in the context of scaling up urban urine collection, transport, and fertilization in São Paulo, Brazil.