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Ecological sanitation

Excreta reuse in dry sanitation systems[edit]
The recovery and use of urine and feces in "dry sanitation systems", i.e. without sewers or without mixing substantial amounts of water with the excreta, has been practiced by almost all cultures. The reuse was not limited to agricultural production. The Romans, for example, were aware of the bleaching attribute of the ammonia within urine and used it to whiten clothing.

Many traditional agricultural societies recognized the value of human waste for soil fertility and practiced the "dry" collection and reuse of excreta. This enabled them to live in communities in which nutrients and organic matter contained in excreta were returned to the soil. Historical descriptions about these practices are sparse, but it is known that excreta reuse was practiced widely in Asia (for example in China, Japan, Vietnam, Cambodia, Korea) but also in Central and South America. However, the most renowned example of the organised collection and use of human excreta to support food production is that of China. The value of "night soil" as a fertilizer was recognized with well-developed systems in place to enable the collection of excreta from cities and its transportation to fields. The Chinese were aware of the benefits of using excreta in crop production more than 2500 years ago, enabling them to sustain more people at a higher density than any other system of agriculture.

In Mexico the Aztec culture collected human excreta for agricultural use. One example of this practice has been documented for the Aztec city of Tenochtitlan which was founded in 1325 and was one of the last cities of pre-Hispanic Mexico (conquered in 1521 by the Spanish): The population placed the sweepings in special boats moored at docks around the city. Mixtures of sweepings and excreta were used to fertilize the chinampas (agricultural fields) or to bolster the banks bordering the lake. Urine was collected in containers in all houses, then mixed with mud and used as a fabric dye. The Aztecs recognized the importance of recycling nutrients and compounds contained in wastewater.

In Peru, the Incas had a high regard for excreta as a fertilizer, which was stored, dried and pulverized to be utilized when planting maize.

In the Middle Ages, the use of excreta and greywater in agricultural production was the norm. European cities were rapidly urbanizing and sanitation was becoming an increasingly serious problem, whilst at the same time the cities themselves were becoming an increasingly important source of agricultural nutrients. The practice of directly using the nutrients in excreta and wastewater for agriculture therefore continued in Europe into the middle of the 19th century. Farmers, recognizing the value of excreta, were eager to get these fertilizers to increase production and urban sanitation benefited. This practice was also called gong farmer in England but carried many health risks for those involved with transporting the excreta and fecal sludge.

Traditional forms of sanitation and excreta reuse have continued in various parts of the world for centuries and were still common practice at the advent of the Industrial Revolution. Even as the world became increasingly more urbanised, the nutrients in excreta collected from urban sanitation systems without mixing with water were still used in many societies as a resource to maintain soil fertility, despite rising population densities.

Decline in recovery of nutrients from human excreta in dry systems[edit]
Recovery of nutrients from excreta in non-sewered sanitation systems was addressing the sanitation problems in settlements in Europe and elsewhere and was contributing to securing agricultural productivity. However, the practice did not become the dominant approach to urban sanitation in the 20th century and was gradually replaced with sewer-based sanitation systems without nutrient recovery (apart from agricultural reuse of sewage sludge in some cases) – at least for cities that can afford it.

There were four main driving factors that led to the demise in the recovery and use of excreta and greywater from European cities in the 19th century:


 * Growth of urban settlements and increasing distance from agricultural fields.
 * Increasing water consumption and use of flush toilet: Water flushing greatly increased the volume of sewage, at the same time diluting the nutrients, making it virtually impossible for them to be recovered and reused as they previously were.
 * Production of cheap synthetic fertilizers, making any efforts to recover and reuse the nutrients and organic material from the large volumes of sewage obsolete.
 * Political intervention as a consequence of the perceived need for a change with regards to how to deal with odorous substances: Up until the end of the nineteenth century the dominant theory on the spread of illness was the miasma theory. This theory stated that everything that smelled had to be gotten rid of because inhaling bad smells was thought to lead to illness.

The use of (odorous) animal manure in agriculture has continued through to this day, probably because the odor of manure was not thought to contribute to human illnesses.

The recovery of nutrients from wastewater still continues in two forms:


 * Wastewater reuse or resource recovery: Use of raw, treated or partially treated wastewater for irrigation in agriculture (with the associated health risks if it is done in an improper way which is often the case in developing countries); and
 * Application of sewage sludge to agricultural lands which is not without controversy in many industrialized countries due to the risks of polluting soils with heavy metals and micropollutants if not managed properly (see biosolids).

Throughout history, many areas in the world have used human excreta in dry systems for nutrients in soil. This seems to be an easy, and effective way to fertilize and better the soil. There is large debate about whether or not this could contain contaminants such as pathogens, organic pollutants, and heavy metals in the sludge, which many people have a concern with since there is a chance it could be harming our environment. The other side of this argument is that overtime, deforestation, industrial agriculture, and over-development have taken so much from the environment without giving anything back, when ecological sanitation is a way of giving back to the environment and helping the soil. This idea of ecological sanitation is also thought to reduce carbon emissions, save water quality, and help the environment in many ways.

Harder, Robin; Wielemaker, Rosanne; Larsen, Tove A.; Zeeman, Grietje; Öberg, Gunilla (2019-04-18). "Recycling nutrients contained in human excreta to agriculture: Pathways, processes, and products". Critical Reviews in Environmental Science and Technology. 49 (8): 695–743.

"What is Ecological Sanitation?". Occidental Arts & Ecology Center. Retrieved 2020-11-24.

"Understanding sustained use of ecological sanitation in rural Burkina Faso". Science of The Total Environment. 613-614: 140–148. 2018-02-01.