Use of Human Excreta from Urine-Diversion Toilets in Food Gardens: Agronomic and Health Aspects

Use of Human Excreta from Urine-Diversion Toilets in Food Gardens: Agronomic and Health Aspects
Report No 1439/3/06
June 2006

EXECUTIVE SUMMARY

BACKGROUND

This report forms part of the output of Water Research Commission project number K5/1439 entitled “Strategy for the furtherance of knowledge and good practice of ecological sanitation (ecosan) technology in South Africa”. The aims of this research project were as follows:

To establish the current “state of the art” in ecological sanitation (ecosan).
To determine:
1. the nature of processes taking place in the vault of a urine-diversion (UD) toilet; and
2. the relevant pathogen destruction parameters in order to increase understanding of the health aspects of UD toilet operation and maintenance (O&M), as well as safety criteria for use of the processed excreta.
To explore appropriate practices for faeces collection and disposal, in order to facilitate the abovementioned safe O&M of the toilets.
To produce a report describing the research conducted for the project, with conclusions and recommendations for improving the future implementation of UD sanitation projects.

REPORT STRUCTURE

The literature review of this study was published by the Water Research Commission as Report no. TT246/05. The other outputs emanating from this study are presented in four separate volumes.

The four volumes are:

Volume 1: 1439/1/06 – Pathogen destruction in UD sanitation systems
Volume 2: 1439/2/06 - Use and acceptance of UD sanitation systems in South Africa
Volume 3: 1439/3/06 - Use of human excreta from UD toilets in food gardens: Agronomic and health aspects (this volume)
Volume 4: TT275/06 - Guidelines for the design, operation and maintenance of UD sanitation systems.

SUMMARY OF THIS VOLUME

This volume is presented in four chapters:

Chapter 1: Introduction

The background and content of the whole project is described, in order that this volume can be put into context.

Chapter 2: Field and glasshouse trials: Use of human excreta in agriculture and food gardens

Due to the emphasis on use of human excreta from ecosan toilets in many countries, there is a fair amount of international literature on the subject of increased crop yields resulting from this practice. Prior to this project, however, no work had been done in South Africa on the subject and the intention of this part of the research was to go some way in addressing the matter. An important motivational issue was the need to find ways of reducing poverty and improving family nutrition in South Africa, particularly among the poor.

Agronomic investigations were conducted into the use of dehydrated faecal material from UD toilets for growing of spinach and cabbage. This was followed by trials using human urine on cabbage, spinach, maize and tomato.

Application of dehydrated human manure from UD toilets resulted in better cabbage and spinach yields than goat kraal manure, but was inferior to inorganic fertiliser. The human manure was a better source of phosphorus for both cabbage and spinach than goat kraal manure, indicating that its use would improve the nutrition of crops in most areas of South Africa where soils are inherently deficient in phosphorus. In addition, when ash is used as a bulking/sanitising agent, the human manure has an alkaline pH and thus has a liming effect on acidic soils, which has the potential for improving crop growth.

Diluted human urine was also found to be a good source of nutrients, especially nitrogen, for cabbage and spinach. The application rate is important, however, as too frequent applications tend to depress yields through increased soil salinity. Good results were also evidenced in maize and tomato crops and urine is considered to be as effective agronomically as urea or ammonium sources of nitrogen.

It was concluded that, provided pathogenic tests proved the use of human manure and urine to have a low potential for disease transmission, the use of these products in agriculture and food gardens should be encouraged. Conclusions regarding health aspects are considered in chapter 3.

Chapter 3: Field trials: Microbiological effects on food crops fertilised with faecal material from urine-diversion toilets

As a logical extension to the previous chapter there was a need to establish the safety, from a health point of view, of using faecal material originating from UD toilets as a soil amendment for crop growing purposes. Pathogens can be recycled to humans if improper agricultural practices are implemented.

The same faecal material used for the field investigation described in Volume 1 of this report was used as a soil amendment in the cultivation of spinach and carrots. Detailed microbiological tests were conducted on this material as well as on the in situ soil before sowing and after harvesting, on the irrigation water, and on the harvested crops.

Faecal material extracted from UD toilets in the eThekwini region of South Africa and left in a heap exposed to the weather for four months, after being stored in the toilet vaults for between one and six months, had a microbial content comparable to sludge classified as Type B in the current South African regulations. This complies with the standard for use in agriculture considering some restrictions to minimise human exposure. Applying different rates of material to spinach and carrots, two common edible crops, it was found that the bacteria and fungi content were only noticeable for the higher application rates (>35t/ha), while the helminth ova content varied, both in leaves and stems, depending on the quantity of material applied. Helminth ova content was, for both crops, more prevalent in leaves, suggesting that the ova adhere preferentially to plants rather than soil. Some health risks are therefore inherent in the handling and consumption of food crops grown in soils amended with faecal material from UD toilets.

Faecal material that has been stored for a shorter time will in all likelihood exhibit different results in terms of pathogen transfer to these crops. To assess the actual health risk of helminth ova consumption, for instance, the storage time and final viability on crops need to be considered as well as the infective dose for farmers and consumers and the daily diet of vegetables in the region.

Chapter 4: Conclusions

Application of dehydrated human manure from urine-diversion (UD) toilets on cabbage and spinach crops resulted in better yields than goat kraal manure, but was inferior to inorganic fertiliser. The human manure was also a better source of phosphorus for both cabbage and spinach than goat kraal manure. In addition, when ash is used as a bulking/sanitising agent, the human manure has an alkaline pH and thus has a liming effect on acidic soils.

Diluted human urine was also found to be a good source of nutrients, especially nitrogen, for cabbage and spinach. The application rate is important, however, as soil salinity may be a problem in some soils. Good results were also evidenced in maize and tomato crops. Urine is thus considered to be as effective agronomically as urea or ammonium sources of nitrogen.

It is concluded that, provided pathogenic tests prove the use of human manure and urine to have a low potential for disease transmission, the use of these products in agriculture and food gardens should be encouraged.

Faecal material extracted from UD toilets was applied at different rates to spinach and carrot crops. It was found that the bacteria and fungi content were only noticeable for the higher application rates (>35t/ha), while the helminth ova content varied, both in leaves and stems, depending on the quantity of material applied. Helminth ova content was, for both crops, more prevalent in leaves, suggesting that the ova adhere preferentially to plants rather than soil. Some health risks are therefore inherent in the handling and consumption of food crops grown in soils amended with faecal material from UD toilets.

While the use of human urine and human manure were seen to be effective agronomically, suitable precautions should be taken, for health reasons, to sanitise the excreta (particularly faecal material) before applying them to cropland.