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:
- the nature of processes
taking place in the vault of a urine-diversion (UD) toilet; and
- 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.