Jump to content

Reuse of human excreta: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Line 80: Line 80:


=== Pharmaceutical residues ===
=== Pharmaceutical residues ===
Exreta from humans and farmed animals contain [[hormones]] and [[pharmaceutical drug|pharmaceutical]] residues which could in theory enter the food chain via fertilised crops but are currently not fully removed by conventional wastewater treatment plants anyway and can enter drinking water sources via household wastewater (sewage).<ref name=":Winker"/> The pharmaceutical residues in the excreta are degraded better in the soil than in aquatic systems because "Terrestrial systems (soil) are more suitable for natural degradation of pharmaceuticals than aquatic systems."<ref name=":Winker"/>
Exreta from humans and farmed animals contain [[hormones]] and [[pharmaceutical drug|pharmaceutical]] residues which could in theory enter the food chain via fertilised crops but are currently not fully removed by conventional wastewater treatment plants anyway and can enter drinking water sources via household wastewater (sewage).<ref name=":Winker">von Münch, E., Winker, M. (2011). [http://www.susana.org/en/resources/library/details/875 Technology review of urine diversion components - Overview on urine diversion components such as waterless urinals, urine diversion toilets, urine storage and reuse systems.] Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH</ref> The pharmaceutical residues in the excreta are degraded better in the soil than in aquatic systems because "Terrestrial systems (soil) are more suitable for natural degradation of pharmaceuticals than aquatic systems."<ref name=":Winker"/>


== Other uses ==
== Other uses ==

Revision as of 23:23, 1 January 2015

Application of urine on a field near Bonn, Germany, by means of flexible hose close to the soil

Reuse of excreta (alternative spelling: re-use) refers to the safe use of human excreta (faeces and urine) or animal excreta primarily as soil conditioner and fertilizer in agriculture, gardening or aquaculture, although other uses are possible as well (e.g. building material, biofuel). Some sources call this practice "use of excreta" rather than "reuse" as strictly speaking it is the first use of excreta, not a second use. Reuse of excreta is one example of resource recovery of the resources contained in excreta, mainly the plant-available nutrients nitrogen, phosphorus, potassium as well as micronutrients such as sulphur and organic matter.

These resources which are contained in wastewater, excreta and greywater have traditionally been reused in agriculture in many countries and are still being reused in agriculture to this day - unfortunately often in an unregulated and unsafe manner for example in many developing countries (e.g. Mexico, India, Bangladesh, Ghana). The WHO Guidelines from 2006 have set up a framework how this reuse can be done safely by following a multiple barrier approach.[1] Reuse of sanitised excreta in agriculture has also been called a "closing the loop" approach for sanitation and agriculture and is central to the ecological sanitation approach.

Reuse of excreta is the final step of the sanitation chain which starts with collection of excreta (by use of toilets) and continues with transport and treatment (wastewater treatment is one example) all the way to either disposal or reuse.[2]

Design considerations

Basil plants: The plants on the right are not fertilised, while the plants on the left are fertilised with urine - in a nutrient-poor soil

Research into how to make reuse of urine and faeces safe in agriculture was carried out in Sweden since the 1990s. [3] In 2006 the World Health Organisation (WHO) provided guidelines on safe reuse of wastewater, excreta and greywater.[1] The multiple barrier concept to reuse, which is the key cornerstone of this publication, has led to a clear understanding on how excreta reuse can be done safely.

Types

Urine

Application of urine on eggplants during a comprehensive urine application field testing study at Xavier University, Philippines

Urine contains large quantities of nitrogen (mostly as urea), as well as significant quantities of dissolved phosphates and potassium, the main macronutrients required by plants. The nutrient concentrations in urine vary with diet.[3]

Undiluted urine can chemically burn the roots of some plants which is way it is usually applied diluted with water, which also reduces odour development during application.[4] When diluted with water (at a 1:5 ratio for container-grown annual crops with fresh growing medium each season,[5] or a 1:8 ratio for more general use[6]), it can be applied directly to soil as a fertilizer. The fertilization effect of urine has been found to be comparable to that of commercial fertilizers with an equivalent NPK rating.[7] Conversely, concentrations of heavy metals such as lead, mercury, and cadmium, commonly found in solid human waste, are much lower in urine.

The more general limitations to using urine as fertilizer then depend mainly on the potential for buildup of excess nitrogen (due to the high ratio of that macronutrient),[5] and inorganic salts such as sodium chloride, which are also part of the wastes excreted by the renal system. The degree to which these factors impact the effectiveness depends on the term of use, salinity tolerance of the plant, soil composition, addition of other fertilizing compounds, and quantity of rainfall or other irrigation.

Urine can also be used safely as a source of complementary nitrogen in carbon-rich compost.[6]

Urine typically contains 70% of the nitrogen and more than half the phosphorus and potassium found in urban waste water flows, while making up less than 1% of the overall volume. Human urine can be collected with sanitation systems that utilise urinals or urine diversion toilets. Thus far, source separation, or urine diversion systems have been implemented in South Africa, China, Sweden and many other countries. Since about 2011, the Bill and Melinda Gates Foundation is providing research funding sanitation systems that recover the nutrients in urine.[8]

"Urine management" is a relatively new way of closing the cycle of agricultural nutrient flows (also called ecological sanitation or ecosan) and - possibly - reducing sewage treatment costs and ecological consequences such as eutrophication resulting from the influx of nutrient rich effluent into aquatic or marine ecosystems.[9] The risks of using urine as a natural source of agricultural fertilizer are generally regarded as negligible or acceptable. In fact, some research has shown that there are potentially more environmental problems and a higher energy consumption when urine is treated as part of sewage in wastewater treatment plants compared with when it is used undiluted as a resource.[10]

It is unclear whether source separation, urine diversion, and on-site urine treatment can be made cost effective; nor whether required behavioral changes would be regarded as socially acceptable, as the largely successful trials performed in Sweden may not readily generalize to other industrialized societies.[7] In developing countries the use of whole raw sewage (night soil) has been common throughout history, yet the application of pure urine to crops is rare. Increasingly there are calls for urine's use as a fertilizer, such as a Scientific American article "Human urine is an effective fertilizer".[11]

If urine is to be collected for use as a fertiliser in agriculture, then the easiest method of doing so is (in increasing order of costs) by using waterless urinals, urine-diverting dry toilets (UDDTs) or urine diversion flush toilets.[1]

Urine use in organic farming

The European Union (EU) only allows the use of source separated urine in conventional farming, but not yet in organic farming. This is a situation that many agricultural experts, especially in Sweden, would like to see changed[12]

Dried faeces

Gardeners of Fada N'Gourma in Burkina Faso apply dry excreta after mixing with other organic fertilizer (donkey manure, cow manure) and pure fertile soil, and after maturing for another 2 to 4 months

Reuse of dried faeces from urine-diverting dry toilets (UDDTs) after post-treatment can result in increased crop production through fertilizing effects of nitrogen, phosphorus, potassium and improved soil fertility through organic carbon.[13]

Composted faeces

Main article: Uses of compost

Compost derived from composting toilets (where organic kitchen waste is in some cases also added to the composting toilet), has in principal the same uses as compost derived from other organic waste products, such as sewage sludge or municipal organic waste. One limiting factor may be legal restrictions due to the possibility that pathogens remain in the compost. In any case, the use of compost from composting toilets in one's own garden can be regarded as safe and is the main method of use for compost from composting toilets. Hygienic measures for handling of the compost must be applied by all those people who are exposed to it, e.g. wearing gloves and boots.

Some of the urine will be part of the compost, although some urine will be lost via leachate and evaporation. Urine can contain up to 90 percent of the nitrogen, up to 50 percent of the phosphorus, and up to 70 percent of the potassium present in human excreta.[14]

The nutrients in compost from a composting toilet have a higher plant availability than the product (dried faeces) from a urine-diverting dry toilet.[13]

Faecal sludge

Faecal sludge (also called septage) is defined as "coming from onsite sanitation technologies, and has not been transported through a sewer." Examples of onsite technologies include pit latrines, unsewered public ablution blocks, septic tanks and dry toilets. Faecal sludge can be treated by a variety of methods to render it suitable for reuse in agriculture. These include (usually carried out in combination): dewatering, thickening, drying (in sludge drying beds), composting, pelletisation, anaerobic digestion.[15]

Municipal wastewater

Work by the International Water Management Institute has led to a better understanding on how reuse of municipal wastewater (ideally not containing significant industrial wastewater) can be safely implemented in practice, for which they won the Stockholm Water Prize in 2012.[16]

Animal manure

Animal dung (manure) has been used for centuries as a fertilizer for farming, as it improves the soil structure (aggregation), so that it holds more nutrients and water, and becomes more fertile. Animal manure also encourages soil microbial activity, which promotes the soil's trace mineral supply, improving plant nutrition. It also contains some nitrogen and other nutrients that assist the growth of plants.

Manures with a particularly unpleasant odor (such as slurry from intensive pig farming) are usually knifed (injected) directly into the soil to reduce release of the odor. Manure from pigs and cattle is usually spread on fields using a manure spreader. Due to the relatively lower level of proteins in vegetable matter, herbivore manure has a milder smell than the dung of carnivores or omnivores. However, herbivore slurry that has undergone anaerobic fermentation may develop more unpleasant odors, and this can be a problem in some agricultural regions. Poultry droppings are harmful to plants when fresh but, after a period of composting, are valuable fertilizers.

Manure is also commercially composted and bagged and sold retail as a soil amendment.[citation needed]

Health aspects

Pathogens

Exposure by farm workers to untreated excreta constitute a significant health risk due to its pathogen content. This risk also extends to consumers of crops fertilised with untreated excreta. Therefore, excreta need to be appropriately treated before reuse and health aspects need to be managed for all reuse applications as the excreta can contain pathogens even after treatment.

As an indicator organism in reuse schemes, helminth eggs are commonly uses as these organisms are the most difficult to destroy in most treatment processes. The multiple barrier approach is recommended where e.g. lower levels of treatment may be acceptable when combined with other post-treatment barriers along the sanitation chain.[1]

Pharmaceutical residues

Exreta from humans and farmed animals contain hormones and pharmaceutical residues which could in theory enter the food chain via fertilised crops but are currently not fully removed by conventional wastewater treatment plants anyway and can enter drinking water sources via household wastewater (sewage).[17] The pharmaceutical residues in the excreta are degraded better in the soil than in aquatic systems because "Terrestrial systems (soil) are more suitable for natural degradation of pharmaceuticals than aquatic systems."[17]

Other uses

Apart from use in agriculture, there are other possible uses of excreta. For example in the case of faecal sludge, it can be treated and then serve as protein (black soldier fly process), fodder, fish food, building materials and biofuels (biogas from anaerobic digestion, incineration or co-combustion of dried sludge, pyrolysis of faecal sludge, biodiesel from faecal sludge).[15]

References

  1. ^ a b c d WHO (2006). WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater - Volume IV: Excreta and greywater use in agriculture. World Health Organization (WHO), Geneva, Switzerland
  2. ^ Tilley, E., Ulrich, L., Lüthi, C., Reymond, Ph., Zurbrügg, C. Compendium of Sanitation Systems and Technologies - (2nd Revised Edition). Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland. ISBN 978-3-906484-57-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
  3. ^ a b Joensson, H., Richert Stintzing, A., Vinneras, B., Salomon, E. (2004). Guidelines on the Use of Urine and Faeces in Crop Production. Stockholm Environment Institute, Sweden
  4. ^ Richert, A., Gensch, R., Jönsson, H., Stenström, T., Dagerskog, L. (2010). Practical guidance on the use of urine in crop production. Stockholm Environment Institute (SEI), Sweden
  5. ^ a b Morgan, Peter (2004). "10. The Usefulness of urine". An Ecological Approach to Sanitation in Africa: A Compilation of Experiences (CD release ed.). Aquamor, Harare, Zimbabwe. Retrieved 6 December 2011.{{cite book}}: CS1 maint: location missing publisher (link)
  6. ^ a b Steinfeld, Carol (2004). Liquid Gold: The Lore and Logic of Using Urine to Grow Plants. Ecowaters Books. ISBN 978-0-9666783-1-4.
  7. ^ a b M. Johansson (2001). "Urine Separation – Closing the Nitrogen Cycle" (PDF). Stockholm Water Company. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ von Muench, E., Spuhler, D., Surridge, T., Ekane, N., Andersson, K., Fidan, E. G., Rosemarin, A. (2013). Sustainable Sanitation Alliance members take a closer look at the Bill & Melinda Gates Foundation’s sanitation grants. Sustainable Sanitation Practice (SSP) Journal, Issue 17, EcoSan Club, Austria
  9. ^ Ganrot, Zsofia (2005). Ph.D. Thesis: Urine processing for efficient nutrient recovery and reuse in agriculture (PDF). Goteborg, Sweden: Goteborg University. p. 170.
  10. ^ Maurer, M., Schwegler, P., Larsen, T. A. (2003). Nutrients in urine: energetic aspects of removal and recovery. Water Science and Technology, Vol 48, No 1, pp 37–46
  11. ^ Mara Grunbaum Human urine is shown to be an effective agricultural fertilizer, Scientific American, July 2010. Retrieved on 2011-12-07.
  12. ^ Håkan Jönsson (2001-10-01). "Urine Separation — Swedish Experiences". EcoEng Newsletter 1.
  13. ^ a b Rieck, C., von Münch, E., Hoffmann, H. (2012). Technology review of urine-diverting dry toilets (UDDTs) - Overview on design, management, maintenance and costs. Deutsche Gesellschaft fuer Internationale Zusammenarbeit (GIZ) GmbH, Eschborn, Germany Cite error: The named reference ":1" was defined multiple times with different content (see the help page).
  14. ^ J.O. Drangert, Urine separation systems
  15. ^ a b Linda Strande, Mariska Ronteltap, Damir Brdjanovic (eds.) (2013). Faecal sludge management : systems approach for implementation and operation. IWA Publishing. ISBN 9781780404721. {{cite book}}: |last1= has generic name (help)CS1 maint: multiple names: authors list (link)
  16. ^ Drechsel, P., Scott, C. A., Raschid-Sally, L., Redwood, M., Bahri, A. (eds.) (2010). Wastewater irrigation and health : assessing and mitigating risk in low-income countries (London : Earthscan. ed.). London: Earthscan. ISBN 978-1-84407-795-3. {{cite book}}: |last= has generic name (help)CS1 maint: multiple names: authors list (link)
  17. ^ a b von Münch, E., Winker, M. (2011). Technology review of urine diversion components - Overview on urine diversion components such as waterless urinals, urine diversion toilets, urine storage and reuse systems. Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH
Retrieved from "https://en.wikipedia.org/w/index.php?title=Reuse_of_human_excreta&oldid=640575531"