HOME

TheInfoList



OR:

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 Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include ...
from municipal wastewater. The intended reuse applications for the nutrient content may include:
soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...
or
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
in
agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people ...
or
horticultural Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...
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. There is a large and growing number of treatment options to make excreta safe and manageable for the intended reuse option. Some options include: Urine diversion and dehydration of feces (
urine-diverting dry toilet 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 ma ...
s), composting (
composting toilet 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 b ...
s or external composting processes),
sewage sludge 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 red ...
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. 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 Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolu ...
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 (or domestic sewage, domestic wastewater, municipal wastewater) 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 reside ...
,
sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
. The nutrients and organic matter which are contained in human excreta or in domestic
wastewater Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...
(
sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) 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 reside ...
) 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 A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...
.
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
Guidelines from 2006 have set up a framework describing how this reuse can be done safely by following a "multiple barrier approach".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
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 Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...
are often referred to as wastes (see also
human waste Human waste (or human excreta) refers to the waste products of the human digestive system, menses, and human metabolism including urine and faeces. As part of a sanitation system that is in place, human waste is collected, transported, treate ...
). Within the concept of a
circular economy A circular economy (also referred to as circularity and CE) is a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products as long as possible. CE aim ...
in sanitation, an alternative term that is being used is "resource flows". The final outputs from the
sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
treatment systems can be called "reuse products" or "other outputs". These reuse products are general
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
s,
soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...
s,
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...
, 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 Reuse is the action or practice of using an item, whether for its original purpose (conventional reuse) or to fulfill a different function ( creative reuse or repurposing). It should be distinguished from recycling, which is the breaking down of u ...
" as strictly speaking it is the ''first'' ''use'' of human excreta, not the second time that it is used.


Technologies and approaches

The resources available in wastewater and human excreta include water, plant nutrients,
organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
and energy content.
Sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
systems that are designed for safe and effective recovery of resources can play an important role in a community's overall
resource management In organizational studies, resource management is the efficient and effective development of an organization's resources when they are needed. Such resources may include the financial resources, inventory, human skills, production resources, or ...
. 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 The Sustainable Development Goals (SDGs) or Global Goals are a collection of 17 interlinked objectives designed to serve as a "shared blueprint for peace and prosperity for people and the planet, now and into the future".United Nations (2017) R ...
. It can be efficient to combine wastewater and human excreta with other
organic waste Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane or simple organic molecules by micro-organisms and other living things by composting, aerobic digestion, anaerobic digesti ...
such as
manure Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the Soil fertility, fertility of soil by adding organic ma ...
, food and crop waste for the purposes of resource recovery.Andersson, K., Rosemarin, A., Lamizana, B., Kvarnström, E., McConville, J., Seidu, R., Dickin, S. and Trimmer, C. (2016)
Sanitation, Wastewater Management and Sustainability: from Waste Disposal to Resource Recovery
Nairobi and Stockholm: United Nations Environment Programme and Stockholm Environment Institute.


Treatment options

There is a large and growing number of treatment options to make excreta safe and manageable for the intended reuse option. 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 Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livi ...
. Some treatment options are listed below but there are many more: * Urine diversion and dehydration of feces (which is done with
urine-diverting dry toilet 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 ma ...
s) * Composting (
composting toilet 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 b ...
s or external composting processes) *
Sewage sludge 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 red ...
technologies, which is installed downstream of various
wastewater treatment Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environm ...
technologies * Fecal sludge treatment processes, such as sludge drying beds, constructed wetlands. *
Anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
with biogas production *
Waste-to-energy Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste, or the processing of waste into a fuel source. WtE is a form of energy recovery. Mo ...
process * Omni Processor 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 Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...
cultivation, microbial fuel cell, nitrification and distillation of urine,
struvite Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft min ...
precipitation, incineration, carbonization, solar drying, membranes, filters, alkaline dehydration of urine, ammonia sanitization/urea treatment, lime sanitization.McConville, J., Niwagaba, C., Nordin, A., Ahlström, M., Namboozo, V. and Kiffe, M. (2020)
Guide to Sanitation Resource-Recovery Products & Technologies: A supplement to the Compendium of Sanitation Systems and Technologies
1st Edition. Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, Uppsala, Sweden.


Reuse options

The most common type of reuse of excreta is as fertilizer and soil conditioner in agriculture. This is also called a "closing the loop" approach for
sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
with agriculture. It is a central aspect of the
ecological sanitation Ecological sanitation, commonly abbreviated as ecosan (also spelled eco-san or 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 ch ...
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) or mixed with much water (domestic wastewater or
sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) 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 reside ...
). The most common types of excreta reuse include: *
Fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
and irrigation water in agriculture, and horticulture: for example using recovered and treated water for irrigation; using composted excreta (and other organic waste) or appropriately treated
biosolids Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use ...
as
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
and
soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...
; using treated source-separated urine as
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
. * Energy: for example digesting feces and other organic waste to produce biogas; or producing combustible fuels. * Other: other emerging excreta reuse options include producing protein feeds for livestock using black soldier fly larvae, recovering organic matter for use as building materials or in paper production. Resource recovery from fecal sludge can take many forms, including as a fuel, soil amendment, building material, protein, animal fodder, and water for irrigation. Reuse products that can be recovered from sanitation systems include: Stored
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
, concentrated urine, sanitized blackwater, digestate, nutrient solutions, dry urine, struvite, dried feces, pit humus, dewatered sludge,
compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
, ash from sludge, biochar, nutrient-enriched filter material,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...
, macrophytes, black soldier fly larvae, worms, irrigation water,
aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...
, biogas.


As fertilizer


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. 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. 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. 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 Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th a ...
) etc. Thus, they exhibit a slow-release effect and are usually less rapidly leached compared to mineral fertilizers.


Urine

Urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
contains large quantities of
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
(mostly as
urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...
), as well as reasonable quantities of dissolved
potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
. The nutrient concentrations in urine vary with diet.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
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. Urine's eight main ionic species (> 0.1 meq L−1) are
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
s Na, K, NH4, Ca and the
anions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by con ...
, Cl, SO4, PO4 and HCO3. Urine typically contains 70% of the nitrogen and more than half the
potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
found in
sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) 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 reside ...
, while making up less than 1% of the overall volume. The amount of urine produced by an adult is around 0.8 to 1.5 L per day.
Applying urine as fertilizer has been called "closing the cycle of agricultural nutrient flows" or ecological sanitation or
ecosan Ecological sanitation, commonly abbreviated as ecosan (also spelled eco-san or 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 ch ...
. Urine fertilizer is usually applied diluted with water because undiluted urine can chemically burn the leaves or roots of some plants, causing plant injury, 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. The fertilization effect of urine has been found to be comparable to that of commercial nitrogen fertilizers. Urine may contain pharmaceutical residues ( environmental persistent pharmaceutical pollutants).Winker, M. (2009). ''Pharmaceutical Residues in Urine and Potential Risks related to Usage as Fertiliser in Agriculture'' UHH University Library https://doi.org/10.15480/882.481 Concentrations of heavy metals such as
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
, mercury, and
cadmium Cadmium is a chemical element with the Symbol (chemistry), symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Li ...
, commonly found in sewage sludge, are much lower in urine. 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.Jönsson, H., Richert Stintzing, A., Vinnerås, B. and Salomon, E. (2004
Guidelines on the use of urine and faeces in crop production
EcoSanRes Publications Series, Report 2004-2, Sweden [This source seems to truncate the Jönsson & Vinnerås (2004) table by omitting the potassium row. The full version may be found at the original source a
RG#285858813
!-- -->]
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. These are design values but the actual values vary with diet. Urine's nutrient content, when expressed with the international fertilizer convention of N:P2O5:K2O, is approximately 7:1.5:2.2. Since urine is rather diluted as a fertilizer compared to dry manufactured nitrogen fertilizers such as di-ammonium-phosphate, the relative transport costs for urine are high as a lot of water needs to be transported. 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), and inorganic
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
s such as
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35. ...
, 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. 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. It was reported in 1995 that urine nitrogen gaseous losses were relatively high and plant uptake lower than with labelled
ammonium nitrate Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
. In contrast,
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...
was utilized at a higher rate than soluble phosphate. Urine can also be used safely as a source of nitrogen in carbon-rich
compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
.
Human urine can be collected with
sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
systems that utilize urinals or
urine diversion 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 t ...
toilets. If urine is to be separated and collected for use as a fertilizer in agriculture, then this can be done with
sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
systems that utilize waterless urinals, urine-diverting dry toilets (UDDTs) or
urine diversion 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 t ...
flush toilets. During storage, the urea in urine is rapidly hydrolyzed by
urease Ureases (), functionally, belong to the superfamily of amidohydrolases and phosphotriesterases. Ureases are found in numerous bacteria, fungi, algae, plants, and some invertebrates, as well as in soils, as a soil enzyme. They are nickel-contai ...
, creating
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...
. Further treatment can be done with collected urine to stabilize the nitrogen and concentrate the fertilizer. One low-tech solution to odor is to add
citric acid Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in ...
or
vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...
to the urine collection container, so that the urease is inactivated and any ammonia that do form are less volatile. Besides concentration, simple chemical processes can be used to extract pure substances: nitrogen as nitrates (similar to medieval nitre beds) and phosphorus as
struvite Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft min ...
. 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 Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...
among crop plants, thus minimizing risk of odors, loss of nutrients due to votalization, or transmission of
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...
s. There are potentially more environmental problems (such as
eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phyt ...
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 Sewage (or domestic sewage, domestic wastewater, municipal wastewater) 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 reside ...
in
sewage treatment plants Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding en ...
compared with when it is used directly as a fertilizer resource. 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. Since about 2011, the
Bill and Melinda Gates Foundation The Bill & Melinda Gates Foundation (BMGF), a merging of the William H. Gates Foundation and the Gates Learning Foundation, is an American private foundation founded by Bill Gates and Melinda French Gates. Based in Seattle, Washington, it was l ...
is providing funding for research involving sanitation systems that recover the nutrients in urine.


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.


Dried feces

Reuse of dried
feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a rela ...
(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 Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality.
through organic carbon.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 GmbH, Eschborn, Germany


Composted feces

Compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
derived from
composting toilets 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 ou ...
(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 Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
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 Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
will be part of the compost although some urine will be lost via leachate and evaporation.
Urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
can contain up to 90 percent of the
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
, up to 50 percent of the
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...
, and up to 70 percent of the
potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
present in human excreta. The nutrients in compost from a composting toilet have a higher plant availability than dried feces from a typical
urine-diverting dry toilet 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 ma ...
. 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.Berger, W. (2011)
Technology review of composting toilets - Basic overview of composting toilets (with or without urine diversion).
Deutsche Gesellschaft für Internationale Zusammenarbeit GmbH, Eschborn, Germany


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 Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
, pelletization, and
anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
.


Municipal wastewater

Reclaimed water Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include ...
can be reused for irrigation, industrial uses, replenishing natural water courses, water bodies,
aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characte ...
s 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. Work by the
International Water Management Institute The International Water Management Institute (IWMI) is a non-profit international water management research organisation under the CGIAR with its headquarters in Colombo, Sri Lanka, and offices across Africa and Asia. Research at the Institute foc ...
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.


Sewage sludge

The use of treated
sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
(after treatment also called "
biosolids Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use ...
") as a
soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...
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 Northumbrian Water Limited is a water company in the United Kingdom, providing mains water and sewerage services in the English counties of Northumberland, Tyne and Wear, Durham and parts of North Yorkshire, and also supplying water as Essex an ...
in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...
uses two biogas plants to produce what the company calls "poo power" - using
sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
to produce energy to generate income. Biogas production has reduced its pre 1996
electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describe ...
expenditure of 20 million
GBP Sterling (abbreviation: stg; Other spelling styles, such as STG and Stg, are also seen. ISO code: GBP) is the currency of the United Kingdom and nine of its associated territories. The pound ( sign: £) is the main unit of sterling, and ...
by about 20%. Severn Trent and
Wessex Water Wessex Water Services Limited, known as Wessex Water, is a water supply and sewerage utility company serving an area of South West England, covering 10,000 square kilometres including Bristol, most of Dorset, Somerset and Wiltshire and parts ...
also have similar projects.


Sludge treatment liquids

Sludge treatment liquids (after
anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
) can be used as an input source for a process to recover phosphorus in the form of
struvite Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft min ...
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 Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people ...
, turf and
ornamental plant Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that ...
s sectors as fertilizer under the registered trade name "Crystal Green".


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 Peak phosphorus is a concept to describe the point in time when humanity reaches the maximum global production rate of phosphorus as an industrial and commercial raw material. The term is used in an equivalent way to the better-known term peak ...
") 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 Food security speaks to the availability of food in a country (or geography) and the ability of individuals within that country (geography) to access, afford, and source adequate foodstuffs. According to the United Nations' Committee on World ...
. Therefore, phosphorus from excreta-based fertilizers is an interesting alternative to fertilizers containing mined phosphate ore.


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. In 2006 the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...
(WHO) provided guidelines on safe reuse of wastewater, excreta and greywater. 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.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
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 the 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. Exposure of farm workers to untreated excreta constitutes a significant health risk due to its
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...
content. There can be a large amount of enteric bacteria, virus, protozoa, and helminth eggs in feces. 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 have the potential to inactivate most pathogens. Therefore, thermal sanitization is utilized in several technologies, such as thermophilic composting and thermophilic
anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
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. The treatment of excreta and wastewater for pathogen removal can take place: * at the toilet itself (for example, urine collected from urine-diverting dry toilets is often treated by simple storage at the household level); or * at a semi-centralized level (for example, by
composting Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
); or * at a fully centralized level at
sewage treatment plants Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding en ...
and sewage sludge treatment plants.


Indicator organisms

As an indicator organism in reuse schemes,
helminth Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as ...
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 Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
chain.


Pharmaceutical residues

Excreta from humans contains
hormones A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
and
pharmaceutical A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and ...
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).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 GmbH
In fact, the pharmaceutical residues in the excreta are degraded better in terrestrial systems (soil) than in aquatic systems.


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. 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. High application rates combined with the high water-solubility of nitrate leads to increased
runoff Runoff, run-off or RUNOFF may refer to: * RUNOFF, the first computer text-formatting program * Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed * Runoff or run-off, a stock marke ...
into
surface water Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean. The vast majority of surface water is produced by pre ...
as well as leaching into
groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...
. Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause ' blue baby syndrome' (acquired
methemoglobinemia Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications ...
). The nutrients, especially nitrates, in fertilizers can cause problems for
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
s and for human health if they are washed off into
surface water Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean. The vast majority of surface water is produced by pre ...
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 Fodder (), also called provender (), is any agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food given to the animals (includ ...
, fish food, building materials and
biofuels Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (EIA ...
( biogas from
anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
, incineration or co-combustion of dried sludge, pyrolysis of fecal sludge, biodiesel from fecal sludge).


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. Dried sewage sludge can be burned in sludge incineration plants and generate heat and electricity (the
waste-to-energy Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste, or the processing of waste into a fuel source. WtE is a form of energy recovery. Mo ...
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 Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
.


Hydrogen fuel

Urine has also been investigated as a potential source of hydrogen fuel. Urine was found to be a suitable wastewater for high rate hydrogen production in a
Microbial Electrolysis Cell A microbial electrolysis cell (MEC) is a technology related to Microbial fuel cells (MFC). Whilst MFCs produce an electric current from the microbial decomposition of organic compounds, MECs partially reverse the process to generate hydrogen or ...
(MEC).


Biogas

Small-scale biogas plants are being utilized in many countries, including Ghana, Vietnam and many others. Larger centralized systems are being planned that mix animal and human feces to produce biogas. Biogas is also produced during
sewage sludge 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 red ...
processes with
anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
. Here, it can be used for heating the digesters and for generating electricity. 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.


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. 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.


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.


Precious metals recovery

A Japanese sewage treatment facility extracts
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lu ...
s from
sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
, "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
old Old or OLD may refer to: Places *Old, Baranya, Hungary *Old, Northamptonshire, England * Old Street station, a railway and tube station in London (station code OLD) *OLD, IATA code for Old Town Municipal Airport and Seaplane Base, Old Town, M ...
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." 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.


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 A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen fuel, hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most bat ...
catalysts while performing better.


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. The terms "sanitation economy" and "toilet resources" have been introduced to describe the potential for selling products made from human feces or
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
.


Sale of compost

The NGO Sustainable Organic Integrated Livelihoods, SOIL in Haiti began building
urine-diverting dry toilet 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 ma ...
s and
composting Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
the waste produced for agricultural use in 2006. 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. 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. 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.


Policies

There is still a lack of examples of implemented policy where the reuse aspect is fully integrated in policy and advocacy.SEI (2009)
Sanitation policies and regulatory frameworks for reuse of nutrients in wastewater, human excreta and greywater
- Proceedings from SEI/EcoSanRes2 Workshop in Sweden. Stockholm Environment Institute, Sweden
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).


Regulatory considerations

Regulations such as Global Good agricultural practice, Good Agricultural Practices may hinder export and import of agricultural products that have been grown with the application of human excreta-derived fertilisers.Elisabeth Kvarnström, Linus Dagerskog, Anna Norström and Mats Johansson (2012
Nutrient reuse as a solution multiplier
(SIANI policy brief 1.1), A policy brief by the SIANI Agriculture-Sanitation Expert Group, Sweden


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. 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.


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

In the United States, the EPA regulation governs the management of
sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
but has no jurisdiction over the byproducts of a urine-diverting dry toilet. Oversight of these materials falls to the states.


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. In China, with the impact of the long tradition, human excreta is often used as fertilizer for crops. 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. 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.


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.


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. 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 towards meeting present and future energy needs. In Tororo District in eastern Uganda - a region with severe land degradation problems - smallholding, 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.


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.


See also

*Manure *Ecological sanitation *Fecal sludge management *Night soil, Nightsoil *Resource recovery *
Compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...


Notes


References


External links


Documents on reuse of excreta
in the library of the Sustainable Sanitation Alliance
Photos on reuse of excreta
in photo database of the Sustainable Sanitation Alliance {{Recycling Agriculture Excretion Repurposing Sanitation Feces