Ingredients for lacto-acid fermentation: living Sauerkraut brine (inoculant), bacteria incubation food (milk, sugar or molasses), source-separated urine, recycled milk bin and acidity test kit.

  • INCUBATION — Activating lacto-acid cultures from living sauerkraut brine with hi-carb food at room temperature for 24 hours.

  • INOCULATION — Source-separate urine and collect together with ten percent (by weight) of lacto-acid inoculant.

  • STORAGE — The lacto-acid bacteria need about three weeks (at room temperature) to 'pickle' the urine.

  • pH TESTING — The fermentation is successful when the pH value has decreased to 4.5 or lower (from originally pH 6.8). Without treatment, urine becomes alkaline (pH 9 or higher) after one month.


¹ Waterless Collection of Human Excreta by Application of Lactic Acid Fermentation, Asrat Yemanah, M. Bulbo, H. Factura, C. Bucie, R. Otterpohl, 2012, Institute of Wastewater Management and Water Protection, Hamburg University of Technology.

² Terra Preta Sanitation, Dorotee Spuhler and Robert Gensch, 2010, Institute of Wastewater Management and Water Protection, SSWM Sustainable Sanitation and Water Management, Basel.

Controlled Fermentation

Stabilising urine

The controlled fermentation of urine in the absence of oxygen — contrary to spontaneous, destructive decomposition process — aims to eliminate pathogens and to 'fix' nutrients. Stabilized urine neither releases ammonia nor C0₂. There is a range of microbes suitable to inoculate (kick-start) the substrate. The Nutrients Recovery utilizes two inoculants that can be self-sufficiently produced with simple means:
1) Bacillus subtilis generated with hay infusion (water-soaked, dry weeds) which is a heat-resistant microbe that suppresses soil-born diseases and supports the formation of humus-making enzymes and hormones that nourish plant growth.
2) Lactobacillus cultures derived from homemade sauerkraut brine (pickled cabbage) form citric acid as result of anaerobic metabolism of sugar. The rising acidity — from pH 6.8 to around pH 4.0 — stops the harmful decomposition of complex organic matter¹ (including pathogens and putrescent germs) while the acid-resistant lactobacillus microbes convert the urea into microbial protein. Lacto-fermentation takes place in closed, airtight containment (recycled milk bins) without any offensive emissions.

Once the 'pickled' urine is added to the compost (carbon buffer), microbial protein is gobbled up by other microbes and made 'appetizing' to earth worms (rather than being released back into the atmosphere). Unique in this microbiological conversion is that the synthesis of humus (oxidative amonification) is greater than the concurring respiration of organic matter (degradation with smelly release of ammonia). The significant reduction of undesired respiration in Terra Preta ultimately helps sequester CO₂ into the ground².