Estimating environmental and societal impacts from scaling up urine concentration technologies

There is a growing trend for nutrient recovery from wastewater as part of the transition to a circular economy. Most nutrients in household wastewater originate from urine and one way to facilitate reuse of these nutrients is to concentrate the urine into fertiliser products. Urine concentration technologies are still in the development phase and not implemented at scale. The aim of this study was to provide guidance to technology developers and policymakers by assessing the environmental and societal impacts of urine concentration technologies. In particular, it includes practical aspects such as worker safety, space availability and local fertiliser needs that have not been included in previous studies. Future scenarios on implementing three different urine concentration technologies (alkaline dehydration, nitrification-distillation, ion-exchange with struvite precipitation) in a planned residential area in Malmö, Sweden, were developed. The technologies were evaluated using multi-criteria assessment (MCA), with environment, technical, economic and health sustainability criteria derived from the Sustainable Development Goals (SDGs). It was found that all urine concentration technologies performed well against many of the sustainability criteria examined and can contribute to achieving SDGs, especially regarding nitrogen recovery. Specific areas for further development were identified for each technology. An impact assessment on scaling up demonstrated that nitrogen emissions to surface water were significantly reduced when more than 60% of urine in Malmö city was subjected to urine concentration. Nitrogen and phosphorus recovered from recycling only 15–30% of urine in Malmö could supply 50% of Malmö municipality's fertiliser demand.