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. 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. 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 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.: 5 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. composted feces main article: uses of compost 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. 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. fecal sludge further information: fecal sludge management 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. municipal wastewater further information: reclaimed water and sewage treatment § reuse 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. 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. sewage sludge main articles: sewage sludge and biosolids 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. sludge treatment liquids further information: sewage sludge treatment 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". peak phosphorus further information: 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. health and environmental aspects of agricultural use 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 (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. 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. 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. 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.: 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.: 101 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); or at a fully centralized level at sewage treatment plants and sewage sludge treatment plants. 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. 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). 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 into surface water as well as leaching into groundwater. nitrate levels above 10 mg/l (10 ppm) in groundwater can cause 'blue baby syndrome' (acquired methemoglobinemia). 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). 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 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. 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 (mec). biogas further information: 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 processes with anaerobic digestion. 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 for livestock