Department Process Engineering

As part of the “VUNA” research project, researchers have developed the new VUNA recycling technique by which valuable nutrients can be extracted from urine and used as fertilisers. The liquid fertiliser “Aurin” is the result of the project.

Aurin is produced and marketed by Eawag-Spin-Off (VUNA Ltd) see info box.

Less energy needed for wastewater and fertilisers

Wastewater treatment requires large amounts of energy. In energy-intensive processes, substances such as nitrogen or drug traces have to be removed from wastewater. And conventional methods of producing fertilisers involve using huge amounts of energy to convert nitrogen gas into a useable form. Thanks to the VUNA technique, the problem can be mitigated and energy saved, by collecting undiluted urine and treating it using an energy-efficient method.

100 litres of liquid fertiliser from 1,000 litres of urine

The main prerequisite for this process of nitrogen extraction is the separated collection of urine. This is made possible by special toilets that separate urine and faeces, or water-free urinals. The production of the fertiliser occurs in two stages: first, a biological process stabilises the urine, the nutrients are bound and the urine loses its unpleasant odour. An activated carbon filter ensures that all drug residues are removed from the urine. The liquid fertiliser with high nutrient content is vaporised, thus producing a high quality fertiliser.

Aurin - the end product

Since 2018, “Aurin” has also been approved by the Federal Office for Agriculture for the fertilization of edible plants. The “Aurin Recycling Fertiliser” has been in use since February 2016. This liquid fertiliser contains all the necessary nutrients needed for plant growth – e.g. nitrogen, phosphorous and potassium – as well as a multitude of trace elements such as iron, zinc and boron. 
The fertiliser has been approved in Liechtenstein since 2019 and in Austria since 2022.