Complete Recovery

Panorama of the reactors at the Eawag laboratory. (photo: Peter Penicka)

Nutrients from urine

Our body excretes the majority of nutrients in the urine (and not in the faeces). By collecting urine separately, we can recover valuable nutrients, e.g. nitrogen, phosphorus, potassium, or sulphur. At the same time, we prevent pollution of surface waters with high nutrient loads.

Bacteria transforming urine

To recover all nutrients contained in urine and transform them into a suitable fertiliser product, the combination of two processes has proven to be efficient: In a first step, urine is stabilised in a bacterial process called nitrification. In a subsequent step, the liquid of the stabilised urine is evaporated to separate it from a concentrated nutrient solution or nutrient crystals.

Eawag's fertiliser production

All toilets at Eawag's main building Forum Chriesbach divert the urine into a separate pipe system.
After storage, a pilot-scale treatment unit at the basement transforms the urine into a concentrated nutrient solution. Currently, about 50 L of urine are processed every day, producing on average 2 L of liquid fertiliser and 48 L of distilled water. 

Further readings:

Brochure: Nutrient recovery from Urine [English] - [Français] - [Deutsch]

Udert, K.M., Wächter, M. (2012) [pdf] Complete nutrient recovery from source-separated urine by nitrification and distillation. Water Research 46(2), 453-464.