Toilet compost and human urine used in agriculture: fertilizer value assessment and effect on cultivated soil properties.

Toilet compost (TC) and human urine are among natural fertilizers, which raise interest due to their double advantages to combine sanitation and nutrient recovery. However, combination of urine and TC is not so spread probably because the best ratio (urine/TC) is still an issue and urine effect on soil chemical properties remains poorly documented. This study aims to determine the best ratio of urine and TC in okra cultivation, by targeting higher fertilization effect combined with lower impact on soil chemical properties. Based on Nitrogen requirement of okra, seven treatments were compared: (T0) no fertilizer, (T1) chemical fertilizer (NPK: 14-23-14), (T2) 100% urine, (T3) 100% TC, (T4) ratio of 75% urine+25% TC, (T5) 50% urine+50% TC and (T6) 25% urine+75% TC. Results indicated that T4 (75% urine+25% TC) gave the highest plant height and yield. In contrast, T2 (100% urine) gave the lowest results among all treatments, indicating toxicity effects on plant growth and associated final yield. Such toxicity is confirmed by soil chemical properties at T2 with soil acidification and significant increase in soil salinity. In contrast, application of urine together with TC mitigates soil acidification and salinity, highlighting the efficiency of urine and TC combination on soil chemical properties. However, further investigation is necessary to refine better urine/TC ratio for okra production.

Inactivation mechanisms of pathogenic bacteria in several matrixes during the composting process in a composting toilet.

This study aimed to compare the inactivation rate and the mechanisms of pathogenic bacteria in three matrixes (sawdust, rice husk and charcoal) during the composting process. The inactivation rate was evaluated with Escherichia coli strain and the damaged parts and/or functions were evaluated with three different media. Normalized inactivation rate constant in three media and from three matrixes had no significant difference in each process (pure, 1 month and 2 months). The value in rice husk was relatively increased during 2 months but there was no significant difference. The inactivation rate constants of Tryptic Soy Agar (TSA) and Compact Dry E. coli/Coliform in pure sawdust and rice husk were relatively lower than that of Desoxycholate Agar, but increased in 2 months. This indicated that damaging part was changed from outer membrane to enzymes and metabolisms during the 2-month composting process. In the case of charcoal, only the TSA value in apure matrix was relatively lower than that of others, but it increased in 2 months. This indicated that damaging part was changed from outer membrane and enzyme to metabolisms during the composting process. Composting matrix and composting process did not significantly affect inactivation rate of pathogenic bacteria during the process but affected the damaging part of the bacteria.