Nutrients in a circular economy: Role of urine separation and treatment

The increasing global population, over the last few decades, brought about the rise in synthetic fertiliser market prices along with explosive agricultural demand. Source separation of urine can be one of the most effective solutions for nutrient recovery as a fertiliser, transforming the conventional linear economy into a circular economy. The urine diversion from wastewater can improve conventional wastewater treatment plants to be energy-efficient and cost-effective, as a considerable quantity of nutrients in wastewater is derived from urine. The stabilisation and sanitisation of source separated urine have been studied earlier by applying physical, biological, chemical, and electrochemical treatment processes. Further processes such as evaporation, freeze -thawing, and membrane processes have been investigated to recover as well as concentrate nutrients as a urine-derived fertiliser. As such, this review discusses the urine diversion and collection systems as well as previous technologies for the urine treatment and nutrient recovery. In addition, the industrial research hub funded by Australian Research Council (ARC) which focuses on the Nutrients in a Circular Economy (NiCE) is introduced in this paper. The ARC NiCE hub aims to achieve four themes, including urine collection, processing, fertiliser optimisation, and fertiliser end-use, moving towards a closed circular nutrient economy.

Automated summary

The rising global population has led to increased synthetic fertiliser prices and a surge in agricultural demand. Source separation of urine is an effective solution for nutrient recovery, transforming the linear economy into a circular one. Diverting urine from wastewater improves the energy efficiency and cost-effectiveness of conventional wastewater treatment plants, as a significant amount of nutrients in wastewater come from urine. Various treatment processes, such as physical, biological, chemical, and electrochemical methods, have been studied to stabilise and sanitise source-separated urine. Additionally, processes like evaporation, freeze-thawing, and membrane techniques have been explored to recover and concentrate nutrients for use as urine-derived fertilisers. This review also discusses urine diversion systems, previous urine treatment technologies, and the Australian Research Council (ARC) funded industrial research hub called Nutrients in a Circular Economy (NiCE), which focuses on urine collection, processing, fertiliser optimisation, and end-use for a closed circular nutrient economy.