Science Fair Project Encyclopedia
Night soil is a term most often used to describe the practice of using untreated human waste as fertilizer. This is a highly hazardous practice because of the human disease microbes in human feces. Nevertheless, in the third world it is a common practice. There have been cases of disease-carrying tomatoes, lettuce, and other vegetables being imported from third world nations into more developed nations.
This is sometimes used as a political football to further an agenda. For example, some on the right of the political spectrum in the United States have used the fact that people have gotten sick from vegetables imported from Mexico to argue against NAFTA and even illegal aliens, although the latter relationship is tenuous.
The safe reduction of human waste into compost is possible, but fairly complex. Many municipalities create compost from the city sewage system, but then recommend that it only be used on flower beds, not vegetable gardens. Some claims have been made that this is dangerous or inappropriate without the expensive removal of heavy metals.
India's ancient caste system assigned untouchables with the disposal of night soil. This "manual scavenging" is now illegal in most Indian states, although the practice undoubtedly continues in many rural areas.
The proper disposal or recycling of sewage remains an important research area that is also highly political.
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