Fertilizer recovery from source-separated urine by evaporation with a combined process of dehumidification and the addition of absorbent resin supplement

Abstract

Urine is an ideal resource for producing fertilizer, and processes of volume reduction are promising ways to recover nutrients from urine. Because urea is rapidly hydrolyzed in fresh urine, the stabilization of urine is usually necessary to avoid nitrogen loss during evaporation for fertilizer production. In this work, we investigated a new method about rapid evaporation for non-pretreated urine by dehumidification and addition of absorbent resin supplement (ARS). We obtained the optimum operating parameters, they were: 40 °C of temperature, 40 % of humidity, 460 cm2/ (L urine) of area, and 16.7 g ARS/(L urine). ARS absorbed the urine completely and quickly, and the moisture in the system was collected by the dehumidifier to keep the constant dry treatment area. Formation of a high salt content in the treatment area further inhibited the hydrolysis of urea, and finally, urea crystals were harvested. This study achieved a high water evaporation efficiency of 95 % and a high recovery fraction (92.2 % of nitrogen and 100 % of phosphorus) at a low temperature of 40 °C. The crystals included CO(NH)2 and NH4Cl, which are ideal fertilizers for vegetation. The results of this study demonstrated that dehumidification combined with addition of ARS for source-separated urine dehydration is a cost-effective and green technology for urine nutrition recovery.