Economics of Production and Resource Management: Assessment of the Environmental Impact Associated with Human Waste Fertilizer in Agricultural Production
The objective of this study is to conduct an assessment of the environmental impact associated with human waste fertilizer in agricultural production. National Geographic News reporter Tasha Eichenseher reported that 200 million farmers in developing countries are making use of raw sewage due to water shortages and rising costs of fertilizer to irrigate and fertilize approximately 49 million acres of cropland. It is reported by Eichenseher (2008) that this practice "carries serious health risks for many" however, it is reported that the dangers of the use of human waste fertilizer are "eclipsed by the social and economic gains for poor urban farmers and consumers who need affordable food." (Eichenseher, 2008)
The 200 million farmers reported to be using this type of fertilizer are those in sub-Saharan Africa and Latin America and it is reported that the crops on which this type fertilizer is being used includes harvest grains and vegetables. According to the World Health Organization and reported by Eichenseher (2008) these foods are relied upon by approximately 10% of the world population. The report additionally states that wastewater agricultural has the potential to "both help and hurt great numbers of urban consumers." (Eichenseher, 2008)
Statement of Problem
The health risks associated with the use of human waste fertilizer is that many areas in developing countries there are not wastewater treatment facilities so the waste being used on crops is untreated human waste and when used for irrigation of agriculture the risks include disease-causing bacteria, since the produce is eaten raw and unwashed.
Significance of Study
In fact 2.2 million individuals are known to die each year because of diseases related to diarrhea and this includes that of cholera. Approximately 80% of those cases are linked to "contact with contaminated water and lack of proper sanitation." (Eichenseher, 2008) Gaining a better understanding of the risk factors of the use of human waste fertilizer is critical to avoiding the deaths associated with contamination by this mass.
The methodology of this study is qualitative in nature and to be conducted through an exhaustive base of literature in this area of study. Qualitative study is interpretive and descriptive in nature.
It is held by Pay Drechsel, IWMI environmental scientist, that the "social and economic benefits of using untreated human waste to grow food outweigh the health risks." (Eichenseher, 2008) Addressing these risks includes education of farmers and consumers "while the free water and nutrients from human wastewater and feces can help urban farmers in developing countries to escape poverty." (Eichenseher, 2008) One report states that human excreta is rich in nitrogen and other agriculturally required nutrients and in many ways is believed to be superior to artificial fertilizers. For example if it stated that human excreta:
(1) Encourages the formation of humus (decomposed vegetable matter) which is essential for optimum soil structure and water retention;
(2) Contains trace elements (chemical fertilizers do not) which help protect the plant from parasites and disease;
(3) Promotes the development of small organisms (microbes) which convert the minerals to forms that the plants can use; and (4) Improves the soil structure, making it easier to cultivate and to resist the effects of erosion. (Franceys, Pickford & Reed, 1992)
Common excrete-recycling practices are listed in the following table labeled Figure 1 in this study.
Figure 1 -- Common Excreta-Recycling Practices among World Countries
Countries where used
Soil fertilization with untreated excreta
China, Japan, Korea, Taiwan, Thailand
Composted excreta used in agriculture
Excreta fed to animals
China, India, Melanesia, Nigeria, Sri Lanka
Central America, Vietnam, Europe
China, India, Korea,
China, India, Korea, Malaysia, Indonesia
Aquatic weed production
Vietnam, South-east Asia
Adapted from: Franceys, Pickford & Reed (1992)
Composting is reported as a process that biologically reduces organic matter in the production of the substance known as 'compost' and which is a valuable soil conditioner and fertilizer. The excreta is combined with other matter to bring about a reduction in the moisture content in what is a chemical balance mass and texture adjustment. (Franceys, Pickford & Reed, 2002, paraphrased) When enough organic mass exists where oxygen is present the process will bring about a breakdown resulting in energy release.
The energy is partially utilized by bacteria in reproduction and partially converted to heat. Generation of enough heat raises the mass temperature sufficiently to eliminate the pathogens. At any rate the generation of wastes by only one family would not support such a rise in the temperature resulting in the lack of certainly about pathogenic organisms being destroyed during the process and specifically parasitic worms and cysts. Franceys, Pickford & Reed, 2002, paraphrased)
) Other features must be included in a latrine using this process if disease is not to spread. Also introduced are aerobic latrines, which are required to:
(1) Keep the waste material open and relatively dry to enable free circulation of air;
(2) Keep new and old wastes separate; and (3) Waste containment to the extent that pathogenic organisms can be eliminated. Franceys, Pickford & Reed, 2002, paraphrased)
It is reported that the most common design in aerobic latrines is that called the "Multrum" which was developed in Sweden. Franceys, Pickford & Reed, 2002, paraphrased)
It is reported that excreta and other wastes are added into the receptacle, which is 3m-long and sloping away from the inlet. It is reported that the latrine is "fitted with a suspended floor formed by channels in an 'n' shape which pulls air in past the storage chamber, through the mass of decomposition and leaving through the ventilation pipe. This mass is reported to slide gradually down the suspended floor during the decomposition process and finally landing in the storage compartment where it stays until removal. (Franceys, Pickford & Reed, 2002, paraphrased)
The decomposed excreta remain in the storage compartment approximately one year so that the pathogens die off. The compost chemical balance and moisture levels can be stabilized through the addition of vegetable waste, sawdust or ash in what is reported to be an ongoing process. These latrines in small communities have realized success in industrialized countries however; there is the requirement of fan installation on the ventilation pipe to promote ventilation and to control flies and odor. (Franceys, Pickford & Reed, 2002, paraphrased)
Apparently the primary problem with the latrines is that they were not valued for their end results by those using the latrines. The report states that anaerobic or 'without air' is easier that aerobic 'with air' conditions. Naturally a mass of excreta that contains moisture and other wastes will compact and exclude the air resulting in a mass that is 'anaerobic. The anaerobic latrines are reported to generally work on a "batch system." (Franceys, Pickford & Reed, 2002, paraphrased) In the event that human excreta is combined with "animal and agricultural wastes, and water, it will give off gas as it decomposes. Given the right temperature and mix of wastes, much of the gas will be methane, which is flammable.
Figure 3 -- Double Vault Latrine
Figure 4 -- Continuous Composting Toilet
The mix of gases produced is called 'biogas'. Biogas plants have been incorporated into domestic latrines in a number of countries with mixed success. The plants are used widely in China where the gas produced is used for cooking and lighting" (Franceys, Pickford & Reed, 2002) Biogas plants are stated to store the wastes for approximately 30 days which removes pathogenic organisms for the most part.
It is reported that biogas should ideally be stored for some period of time prior to being placed in the biogas tank. Challenges include that biogas plants are expensive to construct and there is great difficulty in operating these plans. Where poor maintenance occurs then so does loss of as production and digester tanks is blocked with solids. These plants are appropriate in communities who have firm commitment to organic waste recycling and one in where alternative power source potential is very limited. The following illustration shows the biogas tank with latrine.
Figure 4 - Biogas Tank with Latrine
Source: Franceys, Pickford & Reed (1992)
The Environmental Protection Agency Act Sheet entitled "Waste-Derived Fertilizers" states the EPA when determining whether fertilizers contain containments whether waste- or non-waste derived and whether these "pose unacceptable risks to human health or the environment that the EPA assesses the following:
(1) The types of wastes that are being used in fertilizer manufacture, and the composition of fertilizers with regard to toxic metals and other potentially hazardous constituents;
(2) the potential for soil contamination, and associated risks to human health and the environment, from nonbeneficial constituents, based on fertilizer content and application rates;
(3) Incidents of crop damage or other problems thought to be related to waste-derived fertilizer use or fertilizer containing hazardous constituents;
(4) Current regulatory requirements for fertilizer composition in various states and in foreign countries. (Environmental Protection Agency…