ABSTRACT
During storage of urine, urea is biologically decomposed to ammonia, which can be lost via volatilization and cause malodor. Lactic acid fermentation of urine can decrease nitrogen volatilization and reduce odour emissions. Fresh urine (pH = 5.2 - 5.3 and NH4+-N = 1.2 - 1.3 g L−1) was lacto-fermented with bacterial inoculum from sauerkraut and compared to urine stored for 36 days in glass jars. In the lacto-fermented urine, the pH was reduced to 3.8 - 4.5 and the ammonium content by 22 - 30%, while in the untreated urine the pH rose to 6.1 and its ammonium content increased by 32%. The concentration of lactic acid bacteria (LAB) in lacto-fermented urine was 7.3 CFU ml−1, suggesting that urine is a suitable medium for LAB growth.
The perceived odour was twice stronger in the untreated urine than in the lacto- fermented one. Lacto-fermented urine induced higher radish germination than stored urine. Adding LAB inoculum to storage tanks in a urine diverting dry toilet reduced the pH from 8.9 to 7.7, while the ammonium content increased by 35%, probably due to the high initial pH of the urine. As the hydrolyzed (stored) urine has a high buffering capacity for an efficient urine lacto-fermentation, the LAB inoculum should be added to urine storage tanks before urine starts to accumulate there.
