Skip to content Skip to navigation

Urine-Derived Products

Urine is 1% of wastewater volume but contains up to 80% of its nutrients (nitrogen, phosphorus, potassium). Discharges of nitrogen and phosphorus cause eutrophication; conversely, nitrogen and phosphorus are primary constituents in fertilizers. Conventional nitrogen removal from wastewater is a costly and energy-intensive process that converts ammonium (NH4+) to dinitrogen gas (N2). Paradoxically, N2 is converted to NH4+ fertilizers in the energy-intensive Haber-Bosch process. Recovering nitrogen from urine closes the loop between fertilizer production and wastewater treatment, reduces costs and energy required to prevent environmentally harmful discharges, and incentivizes excreta management. Extracting fertilizers from wastewater exemplifies work at the food-energy-water nexus: harvesting nitrogen in wastewater as fertilizer for agriculture reduces the energy demand for nitrogen fixation.

Nitrogen is largely present as NH4+ in urine, and can be preferentially extracted using ion exchange columns and recovered as ammonium sulfate fertilizer. To date we have characterized several adsorbents in terms of adsorption density and regeneration efficiency, as well as the effects of urine parameters on molecular adsorption. At the process scale, we have determined operating parameters for household and large-scale columns. At the systems scale, household ion exchange requires less energy, cost, and has lower greenhouse gas emissions than conventional wastewater treatment and fertilizer production. In the immediate future, we will determine the effects of organic compounds on thermodynamics and kinetics of ammonium adsorption, develop models to predict adsorption in different waste streams, and correlate material properties with adsorption mechanisms to develop novel sorbents.