On-site resource recovery - The AUTARKY toilet

In parallel to the Blue Diversion Toilet, we are developing a toilet that has on-site urine and faeces treatment, the Autarky Toilet. The toilet user interface is the same as the Blue Diversion Toilet, but the urine treatment technology used to recover the nutrients differs. We are developing a chemical urine stabilization method (2A) and a urine volume reduction by evaporation method (2B) for this toilet. The faeces treatment technology and the thermal faeces dewatering and drying followed by combustion will be developed in cooperation with other grantees of the Reinvent the Toilet Challenge. Read more on the AUTARKY website...

2A Stabilization of fresh urine 

The toilet contains a deposit of hydrated lime. Just enough lime is solubilized to increase the urine pH to 12. At this pH, hydrolysis of urea is suppressed, the degasification of ammonia is avoided and the urine is stabilized. Furthermore, viruses and bacteria are inactivated and the biological degradation of organic matter is inhibited, doing away with the typical urine smell. 
Products 
  1. A liquid phosphorous nutrient solution, which requires further drying and becomes a dry phosphorous fertilizer end-product. 
  2. Stabilized urine containing all other nutrients Nitrogen (N), Potassium (K), Sulphur (S). It is liquid and pumped to the top of the evaporation pipes where it enters the second urine treatment process 2B. 
Maintenance
Every two weeks 
  

2B Evaporation of stabilized urine

The stabilized urine trickles down a pipe through which ambient air is drawn by a ventilator. The urine is dried, by saturating the air with water. The water vapour is released through the ventilation pipe.

Product
The dried nutrients deposit on blotting paper inside the pipe and are harvested as a dry NKS fertilizer end product.  








Maintenance
Every few months 
Energy consumption of the urine treatment
The Autarky Toilet's energy consumption is 33% higher than the Blue Diversion Toilet's energy requirements. Additional energy is required to mix the hydrated lime and to pump the stabilized urine. These processes are independent from the energy provided by faeces combustion.
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