Reuse of human excreta

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Harvest of capsicum grown with compost made from human excreta at an experimental garden in Haiti Harvest of peppers at a SOIL experimental garden.jpg
Harvest of capsicum grown with compost made from human excreta at an experimental garden in Haiti

Reuse of human excreta is the safe, beneficial use of treated human excreta after applying suitable treatment steps and risk management approaches that are customized for the intended reuse application. Beneficial uses of the treated excreta may focus on using the plant-available nutrients (mainly nitrogen, phosphorus and potassium) that are contained in the treated excreta. They may also make use of the organic matter and energy contained in the excreta. To a lesser extent, reuse of the excreta's water content might also take place, although this is better known as water reclamation from municipal wastewater. The intended reuse applications for the nutrient content may include: soil conditioner or fertilizer in agriculture or horticultural activities. Other reuse applications, which focus more on the organic matter content of the excreta, include use as a fuel source or as an energy source in the form of biogas.

Contents

There is a large and growing number of treatment options to make excreta safe and manageable for the intended reuse option. [1] Options include urine diversion and dehydration of feces (urine-diverting dry toilets), composting (composting toilets or external composting processes), sewage sludge treatment technologies and a range of fecal sludge treatment processes. They all achieve various degrees of pathogen removal and reduction in water content for easier handling. Pathogens of concern are enteric bacteria, virus, protozoa, and helminth eggs in feces. [2] As the helminth eggs are the pathogens that are the most difficult to destroy with treatment processes, they are commonly used as an indicator organism in reuse schemes. Other health risks and environmental pollution aspects that need to be considered include spreading micropollutants, pharmaceutical residues and nitrate in the environment which could cause groundwater pollution and thus potentially affect drinking water quality.

There are several "human excreta derived fertilizers" which vary in their properties and fertilizing characteristics, for example: urine, dried feces, composted feces, fecal sludge, sewage, sewage sludge.

The nutrients and organic matter which are contained in human excreta or in domestic wastewater (sewage) have been used in agriculture in many countries for centuries. However, this practice is often carried out in an unregulated and unsafe manner in developing countries. World Health Organization Guidelines from 2006 have set up a framework describing how this reuse can be done safely by following a "multiple barrier approach". [3] Such barriers might be selecting a suitable crop, farming methods, methods of applying the fertilizer and education of the farmers.

Terminology

Human excreta, fecal sludge and wastewater are often referred to as wastes (see also human waste). Within the concept of a circular economy in sanitation, an alternative term that is being used is "resource flows". [4] : 10  The final outputs from the sanitation treatment systems can be called "reuse products" or "other outputs". [4] : 10  These reuse products are general fertilizers, soil conditioners, biomass, water, or energy.

Reuse of human excreta focuses on the nutrient and organic matter content of human excreta unlike reuse of wastewater which focuses on the water content. An alternative term is "use of human excreta" rather than "reuse" as strictly speaking it is the firstuse of human excreta, not the second time that it is used. [3]

Technologies and approaches

A sewage farm in Hampshire, England Morestead Sewage Farm - geograph.org.uk - 57146.jpg
A sewage farm in Hampshire, England

The resources available in wastewater and human excreta include water, plant nutrients, organic matter and energy content. Sanitation systems that are designed for safe and effective recovery of resources can play an important role in a community's overall resource management.

Recovering the resources embedded in excreta and wastewater (like nutrients, water and energy) contributes to achieving Sustainable Development Goal 6 and other sustainable development goals. [5]

It can be efficient to combine wastewater and human excreta with other organic waste such as manure, and food and crop waste for the purposes of resource recovery. [6]

Treatment options

There is a large and growing number of treatment options to make excreta safe and manageable for the intended reuse option. [1] Various technologies and practices, ranging in scale from a single rural household to a city, can be used to capture potentially valuable resources and make them available for safe, productive uses that support human well-being and broader sustainability. Some treatment options are listed below but there are many more: [1]

A guide by the Swedish University of Agricultural Sciences provides a list of treatment technologies for sanitation resource recovery: Vermicomposting and vermifiltration, black soldier fly composting, algae cultivation, microbial fuel cell, nitrification and distillation of urine, struvite precipitation, incineration, carbonization, solar drying, membranes, filters, alkaline dehydration of urine, [7] [8] ammonia sanitization/urea treatment, and lime sanitization. [4] Further research involves UV advanced oxidation processes in order to degrade organic pollutants present in the urine before reuse [9] or the dehydration of urine by using acids. [10]

Reuse options

The most common reuse of excreta is as fertilizer and soil conditioner in agriculture. This is also called a "closing the loop" approach for sanitation with agriculture. It is a central aspect of the ecological sanitation approach.

Reuse options depend on the form of the excreta that is being reused: it can be either excreta on its own or mixed with some water (fecal sludge) [11] or mixed with much water (domestic wastewater or sewage).

The most common types of excreta reuse include: [6]

Resource recovery from fecal sludge can take many forms, including as a fuel, soil amendment, building material, protein, animal fodder, and water for irrigation. [11]

Reuse products that can be recovered from sanitation systems include: Stored urine, concentrated urine, sanitized blackwater, digestate, nutrient solutions, dry urine, struvite, dried feces, pit humus, dewatered sludge, compost, ash from sludge, biochar, nutrient-enriched filter material, algae, macrophytes, black soldier fly larvae, worms, irrigation water, aquaculture, and biogas. [4]

As fertilizer

Comparison of spinach field with (left) and without (right) compost, experiments at the SOIL farm in Port-au-Prince, Haiti Spinach experiments at the SOIL farm.jpg
Comparison of spinach field with (left) and without (right) compost, experiments at the SOIL farm in Port-au-Prince, Haiti
Application of urine on a field near Bonn, Germany, by means of flexible hose close to the soil Application of urine (4461921719).jpg
Application of urine on a field near Bonn, Germany, by means of flexible hose close to the soil
Basil plants: The plants on the right are not fertilized, while the plants on the left are fertilized with urine--in a nutrient-poor soil. Reuse of urine - fertilised and not fertilised basil experiment part I (3530514851).jpg
Basil plants: The plants on the right are not fertilized, while the plants on the left are fertilized with urine—in a nutrient-poor soil.
Application of urine on eggplants during a comprehensive urine application field testing study at Xavier University, Philippines Fig 2 - REPULO - urine reuse - Philippines (6519920661).jpg
Application of urine on eggplants during a comprehensive urine application field testing study at Xavier University, Philippines

Comparison to other fertilizers

There is an untapped fertilizer resource in human excreta. In Africa, for example, the theoretical quantities of nutrients that can be recovered from human excreta are comparable with all current fertilizer use on the continent. [6] : 16  Therefore, reuse can support increased food production and also provide an alternative to chemical fertilizers, which is often unaffordable to small-holder farmers. However, nutritional value of human excreta largely depends on dietary input. [2]

Mineral fertilizers are made from mining activities and can contain heavy metals. Phosphate ores contain heavy metals such as cadmium and uranium, which can reach the food chain via mineral phosphate fertilizer. [12] This does not apply to excreta-based fertilizers (unless the human's food was contaminated beyond safe limits to start with), which is an advantage.

Fertilizing elements of organic fertilizers are mostly bound in carbonaceous reduced compounds. If these are already partially oxidized as in the compost, the fertilizing minerals are adsorbed on the degradation products (humic acids) etc. Thus, they exhibit a slow-release effect and are usually less rapidly leached compared to mineral fertilizers. [13] [14]

Urine

Urine contains large quantities of nitrogen (mostly as urea), as well as reasonable quantities of dissolved potassium. [15] The nutrient concentrations in urine vary with diet. [16] In particular, the nitrogen content in urine is related to quantity of protein in the diet: A high protein diet results in high urea levels in urine. The nitrogen content in urine is proportional to the total food protein in the person's diet, and the phosphorus content is proportional to the sum of total food protein and vegetal food protein. [17] : 5  Urine's eight main ionic species (> 0.1 meq L−1) are cations Na, K, NH4, Ca, and the anions, Cl, SO4, PO4, and HCO3. [18] Urine typically contains 70% of the nitrogen and more than half the potassium found in sewage, while making up less than 1% of the overall volume. [15] The amount of urine produced by an adult is around 0.8 to 1.5 L per day. [3]

Applying urine as fertilizer has been called "closing the cycle of agricultural nutrient flows" or ecological sanitation or ecosan. Urine fertilizer is usually applied diluted with water because undiluted urine can chemically burn the leaves or roots of some plants, causing plant injury, [19] particularly if the soil moisture content is low. The dilution also helps to reduce odor development following application. When diluted with water (at a 1:5 ratio for container-grown annual crops with fresh growing medium each season or a 1:8 ratio for more general use), it can be applied directly to soil as a fertilizer. [20] [21] The fertilization effect of urine has been found to be comparable to that of commercial nitrogen fertilizers. [22] [23] Urine may contain pharmaceutical residues (environmental persistent pharmaceutical pollutants). [24] Concentrations of heavy metals such as lead, mercury, and cadmium, commonly found in sewage sludge, are much lower in urine. [25]

Typical design values for nutrients excreted with urine are: 4 kg nitrogen per person per year, 0.36 kg phosphorus per person per year and 1.0 kg potassium per person per year. [17] : 5  Based on the quantity of 1.5 L urine per day (or 550 L per year), the concentration values of macronutrients as follows: 7.3 g/L N; .67 g/L P; 1.8 g/L K. [17] : 5  [26] : 11  These are design values but the actual values vary with diet. [15] [lower-alpha 1] Urine's nutrient content, when expressed with the international fertilizer convention of N:P2O5:K2O, is approximately 7:1.5:2.2. [26] [lower-alpha 2] Since urine is rather diluted as a fertilizer compared to dry manufactured nitrogen fertilizers such as diammonium phosphate, the relative transport costs for urine are high as a lot of water needs to be transported. [26]

The general limitations to using urine as fertilizer depend mainly on the potential for buildup of excess nitrogen (due to the high ratio of that macronutrient), [20] and inorganic salts such as sodium chloride, which are also part of the wastes excreted by the renal system. Over-fertilization with urine or other nitrogen fertilizers can result in too much ammonia for plants to absorb, acidic conditions, or other phytotoxicity. [24] Important parameters to consider while fertilizing with urine include salinity tolerance of the plant, soil composition, addition of other fertilizing compounds, and quantity of rainfall or other irrigation. [16] It was reported in 1995 that urine nitrogen gaseous losses were relatively high and plant uptake lower than with labelled ammonium nitrate.[ citation needed ] In contrast, phosphorus was utilized at a higher rate than soluble phosphate. [18] Urine can also be used safely as a source of nitrogen in carbon-rich compost. [21]

Human urine can be collected with sanitation systems that utilize urinals or urine diversion toilets. If urine is to be separated and collected for use as a fertilizer in agriculture, then this can be done with sanitation systems that utilize waterless urinals, urine-diverting dry toilets (UDDTs) or urine diversion flush toilets. [26] During storage, the urea in urine is rapidly hydrolyzed by urease, creating ammonia. [28] Further treatment can be done with collected urine to stabilize the nitrogen and concentrate the fertilizer. [29] One low-tech solution to odor is to add citric acid or vinegar to the urine collection container, so that the urease is inactivated and any ammonia that do form are less volatile. [27] Besides concentration, simple chemical processes can be used to extract pure substances: nitrogen as nitrates (similar to medieval nitre beds) and phosphorus as struvite. [29]

The health risks of using urine as a source of fertilizer are generally regarded as negligible, especially when dispersed in soil rather than on the part of a plant that is consumed. Urine can be distributed via perforated hoses buried ~10 cm under the surface of the soil among crop plants, thus minimizing risk of odors, loss of nutrients due to votalization, or transmission of pathogens. [30] There are potentially more environmental problems (such as eutrophication resulting from the influx of nutrient rich effluent into aquatic or marine ecosystems) and a higher energy consumption when urine is treated as part of sewage in sewage treatment plants compared with when it is used directly as a fertilizer resource. [31] [32]

In developing countries, the use of raw sewage or fecal sludge has been common throughout history, yet the application of pure urine to crops is still quite rare in 2021. This is despite many publications that advocate the use of urine as a fertilizer since at least 2001. [22] [33] Since about 2011, the Bill and Melinda Gates Foundation is providing funding for research involving sanitation systems that recover the nutrients in urine. [34]

Feces

According to the 2004 "proposed Swedish default values", an average Swedish adult excretes 0.55 kg nitrogen, 0.18 kg phosphorus, and 0.36 kg potassium as feces per year. The yearly mass is 51 kg wet and 11 kg dried, so that wet feces would have a NPK% value of 1.1:0.8:0.9. [17] : 5  [lower-alpha 1] [lower-alpha 3]

Dried feces

Reuse of dried feces (feces) from urine-diverting dry toilets after post-treatment can result in increased crop production through fertilizing effects of nitrogen, phosphorus, potassium and improved soil fertility through organic carbon. [35]

Composted feces

Cabbage grown in excreta-based compost (left) and without soil amendments (right), SOIL in Haiti Cabbage grown in compost.jpg
Cabbage grown in excreta-based compost (left) and without soil amendments (right), SOIL in Haiti

Compost derived from composting toilets (where organic kitchen waste is in some cases also added to the composting toilet) has, in principle, 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. [36]

The nutrients in compost from a composting toilet have a higher plant availability than dried feces from a typical urine-diverting dry toilet. The two processes are not mutually exclusive, however: some composting toilets do divert urine (to avoid over-saturation of water and nitrogen) and dried feces can still be composted. [37]

Fecal sludge

Fecal sludge 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. Fecal 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, pelletization, and anaerobic digestion. [38]

Municipal wastewater

Reclaimed water can be reused for irrigation, industrial uses, replenishing natural water courses, water bodies, aquifers, and other potable and non-potable uses. These applications, however, focus usually on the water aspect, not on the nutrients and organic matter reuse aspect, which is the focus of "reuse of excreta".

When wastewater is reused in agriculture, its nutrient (nitrogen and phosphorus) content may be useful for additional fertilizer application. [39] Work by the International Water Management Institute and others has led to guidelines on how reuse of municipal wastewater in agriculture for irrigation and fertilizer application can be safely implemented in low income countries. [40] [3]

Sewage sludge

The use of treated sewage sludge (after treatment also called "biosolids") as a soil conditioner or fertilizer is possible but is a controversial topic in some countries (such as USA, some countries in Europe) due to the chemical pollutants it may contain, such as heavy metals and environmental persistent pharmaceutical pollutants.

Northumbrian Water in the United Kingdom uses two biogas plants to produce what the company calls "poo power"—using sewage sludge to produce energy to generate income. Biogas production has reduced its pre-1996 electricity expenditure of 20 million GBP by about 20%. Severn Trent and Wessex Water also have similar projects. [41]

Sludge treatment liquids

Sludge treatment liquids (after anaerobic digestion) can be used as an input source for a process to recover phosphorus in the form of struvite for use as fertilizer. For example, the Canadian company Ostara Nutrient Recovery Technologies is marketing a process based on controlled chemical precipitation of phosphorus in a fluidized bed reactor that recovers struvite in the form of crystalline pellets from sludge dewatering streams. The resulting crystalline product is sold to the agriculture, turf, and ornamental plants sectors as fertilizer under the registered trade name "Crystal Green". [42]

Peak phosphorus

In the case of phosphorus in particular, reuse of excreta is one known method to recover phosphorus to mitigate the looming shortage (also known as "peak phosphorus") of economical mined phosphorus. Mined phosphorus is a limited resource that is being used up for fertilizer production at an ever-increasing rate, which is threatening worldwide food security. Therefore, phosphorus from excreta-based fertilizers is an interesting alternative to fertilizers containing mined phosphate ore. [43]

Health and environmental aspects of agricultural use

Pathogens

Multiple barrier concept for safe use in agriculture

Research into how to make reuse of urine and feces safe in agriculture has been carried out in Sweden since the 1990s. [16] In 2006 the World Health Organization (WHO) provided guidelines on safe reuse of wastewater, excreta, and greywater. [3] The multiple barrier concept to reuse, which is the key cornerstone of this publication, has led to a clear understanding of how excreta reuse can be done safely. The concept is also used in water supply and food production, and is generally understood as a series of treatment steps and other safety precautions to prevent the spread of pathogens.

The degree of treatment required for excreta-based fertilizers before they can safely be used in agriculture depends on a number of factors. It mainly depends on which other barriers will be put in place according to the multiple barrier concept. Such barriers might be selecting a suitable crop, farming methods, methods of applying the fertilizer, education of the farmers, and so forth. [44]

For example, in the case of urine-diverting dry toilets secondary treatment of dried feces can be performed at community level rather than at household level and can include thermophilic composting where fecal material is composted at over 50 °C, prolonged storage with a duration of 1.5 to two years, chemical treatment with ammonia from urine to inactivate the pathogens, solar sanitation for further drying or heat treatment to eliminate pathogens. [45] [35]

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. Step 4- Final maturing (beginning) (5012011706).jpg
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.

Exposure of farm workers to untreated excreta constitutes a significant health risk due to its pathogen content. There can be a large amount of enteric bacteria, virus, protozoa, and helminth eggs in feces. [2] This risk also extends to consumers of crops fertilized with untreated excreta. Therefore, excreta needs 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.

Treatment of excreta for pathogen removal

Temperature is a treatment parameter with an established relation to pathogen inactivation for all pathogen groups: Temperatures above 50 °C (122 °F) have the potential to inactivate most pathogens. [4] : 101  Therefore, thermal sanitization is utilized in several technologies, such as thermophilic composting and thermophilic anaerobic digestion and potentially in sun drying. Alkaline conditions (pH value above 10) can also deactivate pathogens. This can be achieved with ammonia sanitization or lime treatment. [4] : 101 

The treatment of excreta and wastewater for pathogen removal can take place:

Indicator organisms

As an indicator organism in reuse schemes, helminth eggs are commonly used 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. [3]

Pharmaceutical residues

Excreta from humans contains hormones and pharmaceutical drug residues which could in theory enter the food chain via fertilized crops but are currently not fully removed by conventional wastewater treatment plants anyway and can enter drinking water sources via household wastewater (sewage). [26] In fact, the pharmaceutical residues in the excreta are degraded better in terrestrial systems (soil) than in aquatic systems. [26]

Nitrate pollution

Only a fraction of the nitrogen-based fertilizers is converted to produce plant matter. The remainder accumulates in the soil or is lost as run-off. [46] This also applies to excreta-based fertilizer since it also contains nitrogen. Excessive nitrogen which is not taken up by plants is transformed into nitrate which is easily leached. [47] High application rates combined with the high water-solubility of nitrate leads to increased runoff into surface water as well as leaching into groundwater. [48] [49] [50] Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause 'blue baby syndrome' (acquired methemoglobinemia). [51] The nutrients, especially nitrates, in fertilizers can cause problems for ecosystems and for human health if they are washed off into surface water or leached through the soil into groundwater.

Other uses

Apart from use in agriculture, there are other possible uses of excreta. For example, in the case of fecal 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 fecal sludge, and biodiesel from fecal sludge). [38] [6]

Fuel

Solid fuel, heat, electricity

Pilot scale research in Uganda and Senegal has shown that it is viable to use dry feces as for combustion in industry, provided it has been dried to a minimum of 28% dry solids. [52]

Dried sewage sludge can be burned in sludge incineration plants and generate heat and electricity (the waste-to-energy process is one example).

Resource recovery of fecal sludge as a solid fuel has been found to have high market potential in Sub-Saharan Africa. [11]

Hydrogen fuel

Urine has also been investigated as a potential source of hydrogen fuel. [53] [54] Urine was found to be a suitable wastewater for high rate hydrogen production in a microbial electrolysis cell (MEC). [53]

Biogas

Small-scale biogas plants are being utilized in many countries, including Ghana, [55] Vietnam [56] and many others. [57] Larger centralized systems are being planned that mix animal and human feces to produce biogas. [52] Biogas is also produced during sewage sludge treatment processes with anaerobic digestion. Here, it can be used for heating the digesters and for generating electricity. [58]

Biogas is an important waste-to-energy resource which plays a huge role in reducing environmental pollution and most importantly in reducing greenhouse gases effect caused by the waste. Utilization of raw material such as human waste for biogas generation is considered beneficial because it does not require additional starters such as microorganism seeds for methane production, and a supply of microorganisms occurs continuously during the feeding of raw materials. [59]

Food source for livestock

Combination outhouses/feeding troughs were used in several countries since ancient times. [60] They are generally being phased out.

Food source to produce protein for animal feed

Pilot facilities are being developed for feeding Black Soldier Fly larvae with feces. The mature flies would then be a source of protein to be included in the production of feed for chickens in South Africa. [52]

Black soldier fly (BSF) bio-waste processing is a relatively new treatment technology that has received increasing attention over the last decades. Larvae grown on bio-waste can be a necessary raw material for animal feed production, and can therefore provide revenues for financially applicable waste management systems. In addition, when produced on bio-waste, insect-based feeds can be more sustainable than conventional feeds. [61]

Building materials

It is known that additions of fecal matter up to 20% by dried weight in clay bricks does not make a significant functional difference to bricks. [52]

Precious metals recovery

A Japanese sewage treatment facility extracts precious metals from sewage sludge, "high percentage of gold found at the Suwa facility was probably due to the large number of precision equipment manufacturers in the vicinity that use [gold]. The facility recently recorded finding 1,890 grammes of gold per tonne of ash from incinerated sludge. That is a far higher gold content than Japan’s Hishikari Mine, one of the world’s top gold mines, [...] which contains 20–40 grammes of the precious metal per tonne of ore." [62] This idea was also tested by the US Geological Survey (USGS) which found that the yearly sewage sludge generated by 1 million people contained 13 million dollars worth of precious metals. [62]

Other materials

With pyrolysis, urine is turned into a pre-doped, highly porous, carbon material termed "urine carbon" (URC). URC is cheaper than current fuel cell catalysts while performing better. [63]

History

The reuse of excreta as a fertilizer for growing crops has been practiced in many countries for a long time.

Society and culture

Economics

Debate is ongoing about whether reuse of excreta is cost effective. [64] The terms "sanitation economy" and "toilet resources" have been introduced to describe the potential for selling products made from human feces or urine. [64] [65]

Sale of compost

The NGO SOIL in Haiti began building urine-diverting dry toilets and composting the waste produced for agricultural use in 2006. [66] SOIL's two composting waste treatment facilities currently transform over 20,000 gallons (75,708 liters) of human excreta into organic, agricultural-grade compost every month. [67] The compost produced at these facilities is sold to farmers, organizations, businesses, and institutions around the country to help finance SOIL's waste treatment operations. [68] Crops grown with this soil amendment include spinach, peppers, sorghum, maize, and more. Each batch of compost produced is tested for the indicator organism E. coli to ensure that complete pathogen kill has taken place during the thermophilic composting process. [69]

Policies

There is still a lack of examples of implemented policy where the reuse aspect is fully integrated in policy and advocacy. [70] When considering drivers for policy change in this respect, the following lessons learned should be taken into consideration: Revising legislation does not necessarily lead to functioning reuse systems; it is important to describe the “institutional landscape” and involve all actors; parallel processes should be initiated at all levels of government (i.e. national, regional and local level); country specific strategies and approaches are needed; and strategies supporting newly developed policies need to be developed). [70]

Regulatory considerations

Regulations such as Global Good Agricultural Practices may hinder export and import of agricultural products that have been grown with the application of human excreta-derived fertilisers. [71] [72]

Urine use in organic farming in Europe

The European Union allows the use of source separated urine only in conventional farming within the EU, but not yet in organic farming. This is a situation that many agricultural experts, especially in Sweden, would like to see changed. [25] This ban may also reduce the options to use urine as a fertilizer in other countries if they wish to export their products to the EU. [71]

Dried feces from urine-diverting dry toilets in the U.S.

In the United States, the EPA regulation governs the management of sewage sludge but has no jurisdiction over the byproducts of a urine-diverting dry toilet. Oversight of these materials falls to the states. [73] [74]

Country examples

China

Treatment disposal of human excreta can be categorized into three types: fertilizer use, discharge and biogas use. Discharge is the disposal of human excreta to soil, septic tank or water body. [75] In China, with the impact of the long tradition, human excreta is often used as fertilizer for crops. [76] The main application methods are direct usage for crops and fruits as basal or top application after fermentation in a ditch for a certain period, compost with crop stalk for basal application and direct usage as feed for fish in ponds. [60] On the other hand, as much as many people rely on human waste as an agricultural fertilizer, if the waste is not properly treated, the use of night soil may promote the spread of infectious diseases. [77]

India

Urine is used as organic manure in India. It is also used for making an alcohol-based bio-pesticide: the ammonia within breaks down lignin, allowing plant materials like straw to be more easily fermented into alcohol.

Kenya

In Mukuru, Kenya, the slum dwellers are worst hit by the sanitation challenge due to a high population density and a lack of supporting infrastructure. Makeshift pit latrines, illegal toilet connections to the main sewer systems and lack of running water to support the flushable toilets present a sanitation nightmare in all Kenyan slums. The NGO Sanergy seeks to provide decent toilet facilities to Mukuru residents and uses the feces and urine from the toilets to provide fertilizer and energy for the market. [78]

Uganda

Reuse of wastewater in agriculture is a common practice in the developing world. In a study in Kampala, although famers were not using fecal sludge, 8% of farmers were using wastewater sludge as a soil amendment. Compost from animal manure and composted household waste are applied by many farmers as soil conditioners. On the other hand, farmers are already mixing their own feed because of limited trust in the feed industry and the quality of products. [79]

Electricity demand is significantly more than the electricity generation and only a small margin of the population nationally has access to electricity. The pellets produced from fecal sludge are being used in gasification for electricity production. Converting fecal sludge for energy could contribute toward meeting present and future energy needs. [80]

In Tororo District in eastern Uganda—a region with severe land degradation problems—smallholder farmers appreciated urine fertilization as a low-cost, low-risk practice. They found that it could contribute to significant yield increases. The importance of social norms and cultural perceptions needs to be recognized but these are not absolute barriers to adoption of the practice. [81]

Ghana

In Ghana, the only wide scale implementation is small scale rural digesters, with about 200 biogas plants using human excreta and animal dung as feedstock. Linking up of public toilets with biogas digesters as a way of improving communal hygiene and combating hygiene-related communicable diseases including cholera and dysentery is also a notable solution within Ghana. [79]

See also

Notes

  1. 1 2 A formula for adjustment of excreta N and P values based on dietary characteristics is found in Jönsson 2004. [17] : 5 
  2. ↑ For the amount of other elements in urine, see Rose 2015 [15] and Rich Earth 2021. [27]
  3. ↑ For the amount of other elements in feces, see Rose 2015. [15]

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A composting toilet is a type of dry toilet that treats human waste by a biological process called composting. This process leads to the decomposition of organic matter and turns human waste into compost-like material. Composting is carried out by microorganisms under controlled aerobic conditions. Most composting toilets use no water for flushing and are therefore called "dry toilets".

<span class="mw-page-title-main">Night soil</span> Archaic term for excreta from latrines

Night soil is a historically used euphemism for human excreta collected from cesspools, privies, pail closets, pit latrines, privy middens, septic tanks, etc. This material was removed from the immediate area, usually at night, by workers employed in this trade. Sometimes it could be transported out of towns and sold on as a fertilizer.

Human waste refers to the waste products of the human digestive system, menses, and human metabolism including urine and feces. As part of a sanitation system that is in place, human waste is collected, transported, treated and disposed of or reused by one method or another, depending on the type of toilet being used, ability by the users to pay for services and other factors. Fecal sludge management is used to deal with fecal matter collected in on-site sanitation systems such as pit latrines and septic tanks.

<span class="mw-page-title-main">Ecological sanitation</span> Approach to sanitation provision which aims to safely reuse excreta in agriculture

Ecological sanitation, commonly abbreviated as ecosan, is an approach to sanitation provision which aims to safely reuse excreta in agriculture. It is an approach, rather than a technology or a device which is characterized by a desire to "close the loop", mainly for the nutrients and organic matter between sanitation and agriculture in a safe manner. One of the aims is to minimise the use of non-renewable resources. When properly designed and operated, ecosan systems provide a hygienically safe system to convert human excreta into nutrients to be returned to the soil, and water to be returned to the land. Ecosan is also called resource-oriented sanitation.

<span class="mw-page-title-main">Sewage sludge treatment</span> Processes to manage and dispose of sludge during sewage treatment

Sewage sludge treatment describes the processes used to manage and dispose of sewage sludge produced during sewage treatment. Sludge treatment is focused on reducing sludge weight and volume to reduce transportation and disposal costs, and on reducing potential health risks of disposal options. Water removal is the primary means of weight and volume reduction, while pathogen destruction is frequently accomplished through heating during thermophilic digestion, composting, or incineration. The choice of a sludge treatment method depends on the volume of sludge generated, and comparison of treatment costs required for available disposal options. Air-drying and composting may be attractive to rural communities, while limited land availability may make aerobic digestion and mechanical dewatering preferable for cities, and economies of scale may encourage energy recovery alternatives in metropolitan areas.

<span class="mw-page-title-main">Biodegradable waste</span> Organic matter that can be broken down

Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane, compost, humus, and simple organic molecules by micro-organisms and other living things by composting, aerobic digestion, anaerobic digestion or similar processes. It mainly includes kitchen waste, ash, soil, dung and other plant matter. In waste management, it also includes some inorganic materials which can be decomposed by bacteria. Such materials include gypsum and its products such as plasterboard and other simple sulfates which can be decomposed by sulfate reducing bacteria to yield hydrogen sulfide in anaerobic land-fill conditions.

<span class="mw-page-title-main">Sustainable sanitation</span> Sanitation system designed to meet certain criteria and to work well over the long-term

Sustainable sanitation is a sanitation system designed to meet certain criteria and to work well over the long-term. Sustainable sanitation systems consider the entire "sanitation value chain", from the experience of the user, excreta and wastewater collection methods, transportation or conveyance of waste, treatment, and reuse or disposal. The Sustainable Sanitation Alliance (SuSanA) includes five features in its definition of "sustainable sanitation": Systems need to be economically and socially acceptable, technically and institutionally appropriate and protect the environment and natural resources.

<span class="mw-page-title-main">Sewage treatment</span> Process of removing contaminants from municipal wastewater

Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. There are a high number of sewage treatment processes to choose from. These can range from decentralized systems to large centralized systems involving a network of pipes and pump stations which convey the sewage to a treatment plant. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. Sewage treatment often involves two main stages, called primary and secondary treatment, while advanced treatment also incorporates a tertiary treatment stage with polishing processes and nutrient removal. Secondary treatment can reduce organic matter from sewage,  using aerobic or anaerobic biological processes. A so-called quarternary treatment step can also be added for the removal of organic micropollutants, such as pharmaceuticals. This has been implemented in full-scale for example in Sweden.

<span class="mw-page-title-main">Human feces</span> Metabolic waste of the human digestive system

Human feces are the solid or semisolid remains of food that could not be digested or absorbed in the small intestine of humans, but has been further broken down by bacteria in the large intestine. It also contains bacteria and a relatively small amount of metabolic waste products such as bacterially altered bilirubin, and the dead epithelial cells from the lining of the gut. It is discharged through the anus during a process called defecation.

<span class="mw-page-title-main">Sewage</span> Wastewater that is produced by a community of people

Sewage is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sub-types of sewage are greywater and blackwater. Sewage also contains soaps and detergents. Food waste may be present from dishwashing, and food quantities may be increased where garbage disposal units are used. In regions where toilet paper is used rather than bidets, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some municipal solid waste and pollutants from industrial wastewater.

<span class="mw-page-title-main">Urine diversion</span> Separate collection of human urine and feces at the point of their production

Urine diversion, also called urine separation or source separation, refers to the separate collection of human urine and feces at the point of their production, i.e. at the toilet or urinal. Separation of urine from feces allows human waste to be treated separately and used as a potential resource. Applications are typically found where connection to a sewer-based sanitation system is not available or areas where water supplies are limited.

<span class="mw-page-title-main">Dry toilet</span> Toilet that operates without flush water

A dry toilet is a toilet which, unlike a flush toilet, does not use flush water. Dry toilets do not use water to move excreta along or block odors. They do not produce sewage, and are not connected to a sewer system or septic tank. Instead, excreta falls through a drop hole.

Resource recovery is using wastes as an input material to create valuable products as new outputs. The aim is to reduce the amount of waste generated, thereby reducing the need for landfill space, and optimising the values created from waste. Resource recovery delays the need to use raw materials in the manufacturing process. Materials found in municipal solid waste, construction and demolition waste, commercial waste and industrial wastes can be used to recover resources for the manufacturing of new materials and products. Plastic, paper, aluminium, glass and metal are examples of where value can be found in waste.

<span class="mw-page-title-main">Urine-diverting dry toilet</span> Dry toilet with separate collection of feces and urine without any flush water

A urine-diverting dry toilet (UDDT) is a type of dry toilet with urine diversion that can be used to provide safe, affordable sanitation in a variety of contexts worldwide. The separate collection of feces and urine without any flush water has many advantages, such as odor-free operation and pathogen reduction by drying. While dried feces and urine harvested from UDDTs can be and routinely are used in agriculture, many UDDT installations do not apply any sort of recovery scheme. The UDDT is an example of a technology that can be used to achieve a sustainable sanitation system. This dry excreta management system is an alternative to pit latrines and flush toilets, especially where water is scarce, a connection to a sewer system and centralized wastewater treatment plant is not feasible or desired, fertilizer and soil conditioner are needed for agriculture, or groundwater pollution should be minimized.

<span class="mw-page-title-main">Omni processor</span> Group of physical, biological or chemical treatments to process fecal sludge

Omni processor is a term coined in 2012 by staff of the Water, Sanitation, Hygiene Program of the Bill & Melinda Gates Foundation to describe a range of physical, biological or chemical treatments to remove pathogens from human-generated fecal sludge, while simultaneously creating commercially valuable byproducts. An omni processor mitigates unsafe methods in developing countries of capturing and treating human waste, which annually result in the spread of disease and the deaths of more than 1.5 million children.

<span class="mw-page-title-main">Fecal sludge management</span> Collection, transport, and treatment of fecal sludge from onsite sanitation systems

Fecal sludge management (FSM) is the storage, collection, transport, treatment and safe end use or disposal of fecal sludge. Together, the collection, transport, treatment and end use of fecal sludge constitute the "value chain" or "service chain" of fecal sludge management. Fecal sludge is defined very broadly as what accumulates in onsite sanitation systems and specifically is not transported through a sewer. It is composed of human excreta, but also anything else that may go into an onsite containment technology, such as flushwater, cleansing materials, menstrual hygiene products, grey water, and solid waste. Fecal sludge that is removed from septic tanks is called septage.

<span class="mw-page-title-main">Container-based sanitation</span> Sanitation system which uses removable containers

Container-based sanitation refers to a sanitation system where toilets collect human excreta in sealable, removable containers that are transported to treatment facilities. This type of sanitation involves a commercial service which provides certain types of portable toilets, and delivers empty containers when picking up full ones. The service transports and safely disposes of or reuses collected excreta. The cost of collection of excreta is usually borne by the users. With suitable development, support and functioning partnerships, CBS can be used to provide low-income urban populations with safe collection, transport and treatment of excrement at a lower cost than installing and maintaining sewers. In most cases, CBS is based on the use of urine-diverting dry toilets.

Waste valorization, beneficial reuse, beneficial use, value recovery or waste reclamation is the process of waste products or residues from an economic process being valorized, by reuse or recycling in order to create economically useful materials. The term comes from practices in sustainable manufacturing and economics, industrial ecology and waste management. The term is usually applied in industrial processes where residue from creating or processing one good is used as a raw material or energy feedstock for another industrial process. Industrial wastes in particular are good candidates for valorization because they tend to be more consistent and predictable than other waste, such as household waste.

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