Potential benefits and environmental life cycle assessment of equipping buildings in dense cities for struvite production from source-separated human urine

Abstract

The risk of a worldwide phosphorus (P) crisis has been predicted in the past ten years by many researchers and organizations who sought alternative resources of P. Source-separation of urine is being widely considered as a suitable waste stream for P recovery to mitigate the shortage of P while also preventing the eutrophication of receiving waters. In dense cities, urine separation and P recovery as struvite can be efficiently implemented in every building. In order to evaluate the impact of the urine separation and P recovery system in buildings, this study determines the potential amounts of P recovered, freshwater saved, and the environmental impacts of the large-scale production of struvite from source-separated human urine in both typical residential and office buildings in dense cities. The results show that the net struvite production amounts in a typical dense city can cover the diammonium phosphate (DAP) fertilizer consumptions in many countries and the net freshwater saving amounts can be up to 47–87 L/(person·d). These benefits can be achieved with less than 0.3% additional energy consumption and 1% additional environmental emissions compared with conventional buildings. Moreover, the use of environmental friendly materials can further reduce the environmental emissions to a significant extent. Therefore, based on the results obtained in this study, the urine separation and P recovery system is strongly recommended to be implemented in buildings of dense cities.