The energy-intensive production and environmental repercussions of synthetic fertilizers pose significant challenges to agricultural sustainability. Nutrient recovery from human urine, an underutilized renewable resource rich in nitrogen (N), phosphorus (P), and potassium (K), offers a low-energy pathway that supports the Sustainable Development Goals (SDGs 6 and 12). This review synthesizes global research on human urine-based fertilization as a sustainable alternative to synthetic inputs using a systematic approach guided by PRISMA 2020 standards. Additionally, bibliometric analysis and techno-agronomic evaluation were performed on 123 peer-reviewed articles published between 2011 and 2025. Key urine stabilization and nutrient recovery technologies, including source separation, membrane filtration, electrodialysis, ion exchange, bio-electrochemical systems and biochar adsorption, are critically assessed. The nutrient recovery efficiencies ranged from 50-95% for N, 40-99% for P, and 80-98% for K, depending on stabilization method and recovery pathways. Agronomic evidence indicates that urine-derived fertilizers can match or exceed mineral fertilizers, with yield improvements of 10-70% compared to unfertilized controls and yields comparable to urea when applied at equivalent N rates. However, major challenges include membrane fouling, energy requirements, odor issues, and the persistence of pharmaceutical contaminants. Unlike earlier reviews that focused mainly on ecological sanitation or individual recovery technologies, this review integrates PRISMA-based systematic screening with bibliometric mapping and comparative techno-agronomic synthesis. It emphasizes research trends, performance indicators, soil health effects, and scalability barriers, providing a comprehensive evidence-based framework to support the adoption of urine-derived fertilizers within a circular nutrient economy.
bio-based fertilizerscircular nutrient managementecological sanitationresource recoverysustainable crop productivityThe author(s) declared that financial support was not received for this work and/or its publication.section-at-acceptanceSoil Biogeochemistry & Nutrient CyclingIntroduction
The current global population of 8.1 billion is predicted to reach 9.7 billion by 2050, with growth largely concentrated in developing countries (1). This rapid demographic expansion is expected to significantly increase global food production requirements and intensify nutrient demand in agriculture. Recent fertilizer outlook assessments indicate that global fertilizer consumption is likely to rise steadily in response to increasing yield requirements, dietary transitions and the need for enhanced cropland productivity. Model-based projections estimate that global fertilizer demand may increase by nearly 35% over the next four decades (2), with an average annual growth rate of about 1.5% for major nutrients, including nitrogen (N; 115.5 Tg), phosphorus (P; 43.8 Tg), and potassium (K; 33.6 Tg) (3). In line with these long-term forecasts, recent global fertilizer outlook reports suggest that total nutrient consumption may exceed 200 million tonnes in 2024-2025, reflecting a recovery from earlier declines and approaching near-record demand levels (4). Furthermore, market-based projections indicate continued growth in fertilizer production and trade, with global fertilizer market volume expected to reach approximately 783 million tonnes by 2035 under current trend scenarios (5).
Among the fertilizer nutrients, N plays a critical role in increasing crop yield and crude protein content (6). Globally, nitrogen use efficiency (NUE) of conventional fertilizers such as urea remains relatively low (typically 30-50%) due to losses through volatilization, leaching and denitrification (7). In comparison, controlled-release fertilizers and enhanced-efficiency fertilizers (e.g., urease and nitrification inhibitors) have been reported to improve NUE by about 10-30% by synchronizing nitrogen release with crop uptake (8). Conversely, organic nutrient sources such as farmyard manure (FYM) and compost generally show lower short-term NUE because nitrogen mineralization is slow and a fraction of applied N becomes temporarily immobilized in soil organic pools (9). Despite its high N content, urea is a significant source of greenhouse gas (GHG) emissions as it is more susceptible to ammonia (NH3) volatilization and nitrate (NO3-) leaching compared to other N fertilizers. This inefficiency drives farmers to overapply N fertilizers, leading to nutrient runoff and groundwater contamination (2).
Additionally, urea production involves reactions between NH3 and carbon dioxide (CO2) under high operating conditions (150-200°C and 150–250 bar), making it an energy-intensive industrial process. The reported energy requirement of approximately 54 MJ kg N-1 and associated CO2 emissions are generally based on cradle-to-gate life cycle assessments, which include feedstock extraction, ammonia synthesis (Haber-Bosch process), urea synthesis, and energy consumption up to the factory gate. Consequently, the urea industry contributes nearly 1.2% of total anthropogenic CO2 emissions (10). To minimize the energy demand and GHG emissions associated with urea while improving NUE, the fertilizer industry is exploring alternate strategies such as using urease inhibitors like NBPT (n-butyl thiophosphoric triamide) and controlled-release fertilizers (11). These approaches synchronize urea release with plant uptake, reduce ammonia volatilization, and minimize environmental harm.
On the other hand, the world is facing a pressing challenge with wastewater management, generating nearly 380 billion m3 annually, with projections indicating a 24% increase by 2030 and 51% by 2050 (12). Asia contributes the largest share of urban wastewater production, generating approximately 159 billion m3 per year, which accounts for 42% of the global total (13). In parallel, around 4.5 billion people lack access to clean sanitation and nearly 2.3 billion people remain without basic sanitation services (14). In densely populated areas, inadequate sewage systems often result in unregulated and hazardous disposal of human excreta, including urine and feces (15). To address this, SDG 6 emphasizes the importance of clean water and sanitation, calling for robust fecal sludge management by 2030 (12).
One potential solution to this crisis is Ecological Sanitation (ECOSAN), which advocates for decentralized household wastewater collection (16). Global wastewater contains a significant quantity of nutrients, including 16.6 Tg of N (43.7 mg L-1), 3.0 Tg of P (7.8 mg L-1), and 6.3 Tg of K (16.5 mg L-1) (13). Recovering these minerals from wastewater could potentially substitute a significant portion of global fertilizer demand, providing approximately 14.4% of N, 6.8% of P, and 18.6% of K (14). With a global NPK nutrient need of 192.9 Tg, wastewater recovery could meet about 13.4% of this need. This would generate an estimated income of 13.6 billion USD, including 9 billion USD from N, and 2.3 billion USD each from P and K (15). Although wastewater contains valuable nutrients, its direct recovery is challenged by high dilution, chemical complexity, and contamination with pathogens, heavy metals, and organic pollutants. While urine represents only a small fraction (<1%) of total domestic wastewater volume, it contains a disproportionately high share of plant-essential nutrients, particularly nitrogen (80-90%) and phosphorus (50-65%), making it a highly promising target for source separation and nutrient recovery (17). This makes source-separated urine a much cleaner, more concentrated, and more energy-efficient substrate for nutrient recovery than mixed wastewater.
Human urine, a major component of wastewater, offers a promising alternative for synthetic fertilizer. Historically, human urine has been used as a plant nutrient source in several ancient civilizations, including Roman and Asian agricultural systems, where urine was valued for its N content. However, its use declined with the rise of industrial fertilizer production in the 20th century. With the current concerns over energy-intensive fertilizer synthesis, water scarcity, and circular nutrient management, interest in urine recycling has re-emerged (18). Each person produces about 550 liters of urine annually, containing 4 kg of N, 0.4 kg of P, and 0.9 kg of K (17). Recycling nutrients from urine could cover approximately 19% of global N fertilizer needs (19), presenting a lower energy and environmental impact than conventional mineral fertilizers while ensuring efficient wastewater management (20). Urine recycling offers dual benefits by supplying both nutrients and water for agriculture, particularly in arid and semi-arid regions (21). In saline-alkali soils, urine-derived fertilizers provide readily available N and soluble P, improving nutrient uptake where high pH levels limit P availability (22).
Moreover, K in urine-based fertilizers boosts crop health and stress tolerance, while organic matter enhances soil structure, increasing aggregation, permeability, and aeration, which promote root growth and water infiltration (17). Urine irrigation also displaces sodium ions, aiding in salt leaching and reducing root zone salinity, thus making soils more suitable for crops (22). However, transporting large quantities of urine presents challenges due to high costs and unpleasant odors, which affect acceptability. Cultural norms, concerns about pharmaceutical residues and hygiene issues further hinder its widespread use (23). Direct application raises environmental and safety concerns due to high N, P and K levels, which can damage plants (24). In recent years, extensive research has explored human urine as a sustainable alternative to synthetic fertilizers. Key areas of focus include source separation and collection (21), agronomic effectiveness (18), public perception (25), stabilization and disinfection methods, transportation challenges, economics and nutrient recovery techniques (26). However, no study has systematically integrated bibliometric mapping with techno-agronomic assessment to quantify global research trends, technology performance and implementation barriers.
Therefore, this review directly addresses the stated objectives by integrating bibliometric insights with a technical assessment of human urine valorization pathways. Objective 1 focuses on analyzing global publication trends, research clusters and collaborative networks to map how scientific interest in urine-based fertilizers has evolved. Objective 2 systematically evaluates nutrient recovery processes, including physicochemical, biological and integrated approaches, in terms of recovery efficiency, operational feasibility and scalability. Objective 3 synthesizes the agronomic performance of urine-derived fertilizers across crops, soils and management systems to determine their effectiveness relative to conventional fertilizers. Finally, objective 4 discusses operational, environmental and socio-cultural challenges influencing adoption, thereby providing a comprehensive and objective-driven evaluation of human urine as a sustainable fertilizer within a circular nutrient economy.
Methodology
This review followed the PRISMA 2020 approach to ensure a transparent and systematic selection of literature (27). A comprehensive search was conducted in Scopus using the keywords “Human Urine” AND “Fertilizer” or “Human Urine” AND “Nutrient,” which initially retrieved 451 records. These were filtered stepwise by publication year (2010–2025), subject area (Environmental Science; Agricultural and Biological Sciences), document type (research articles), publication stage (final), language (English) and open-access availability, resulting in 123 studies for final inclusion. Grey literature sources such as reports, conference proceedings, theses, book chapters and non-peer-reviewed documents were excluded to maintain consistency in quality assessment and to ensure that only peer-reviewed evidence was synthesized. Similarly, non-English publications were excluded due to limitations in accurate interpretation and standardization of extracted data across studies. Eligibility was evaluated using the PICOS framework to ensure that only studies relevant to human urine, nutrient recovery, stabilization technologies, agronomic responses and environmental impacts were considered. Metadata from the selected studies were exported and cleaned before conducting bibliometric analysis using VOSviewer to generate co-occurrence networks, collaboration maps, and thematic clusters. The PRISMA flow diagram summarizes the identification, screening, and inclusion steps (Figure 1A). This combined PRISMA-based systematic screening and bibliometric mapping approach ensured that the evidence synthesized in this review is both comprehensive and methodologically robust.
(A) PRISMA flowchart of systematic literature screening and selection process (B) Keyword co-occurrence cluster network, (C) Overlay visualization by publication year, (D) Country collaboration map, (E) Three-field plot between authors, their countries and keywords, and (F) Annual scientific production over the years.
(a) Flowchart detailing the selection process for a bibliometric study on human urine as fertilizer, showing stages from identification to inclusion of 123 documents. (b) Network visualization graph of keyword co-occurrence, with clusters in different colors indicating relationships among key terms such as human, nutrients, urine, and phosphorus. (c) Overlay visualization of keyword co-occurrence, colored by average publication year ranging from 2018 to 2023. (d) World map highlighting international collaborations, with lines connecting major contributing countries in blue shades. (e) Sankey diagram illustrating relationships among countries, authors, and research themes in the dataset. (f) Bar chart documenting annual scientific production from 2011 to 2025, indicating a rising trend in relevant publications.
The co-occurrence analysis of keywords revealed that research has concentrated around central themes such as “human urine”, “fertilizers”, “nitrogen”, “phosphorus”, “nutrient recovery”, and “sanitation” (Figure 1B). Associated terms like “urea”, “wastewater treatment”, “struvite”, and “decentralized sanitation” were also frequently used. For this analysis, a minimum keyword occurrence threshold was applied in VOSviewer to filter out low-frequency terms and improve network clarity. The threshold was selected iteratively to ensure that only the most representative and recurring keywords were retained, while avoiding noise from rarely occurring terms. Clustering was then generated automatically by VOSviewer using association strength normalization, grouping keywords based on the strength of their co-occurrence links. This suggests a growing recognition of urine’s role in circular economy models and low-input agriculture. However, terms related to long-term soil health, pharmaceutical risk and farmer adoption appeared infrequently, indicating research gaps in these critical areas. An overlay visualization indicated a noticeable shift in focus between 2020 and 2022 towards topics such as “nutrient recycling”, “urine diversion” and “decentralized sanitation”, reflecting an increased emphasis on sustainable sanitation and nutrient reuse (Figure 1C). These shifts in research themes were mirrored in patterns of international collaboration (Figure 1D). Sweden emerged as a key hub, with active partnerships involving countries such as the USA, Germany, South Africa, India and Australia. This pattern reflects growing global interest in the recovery and reuse of nutrients from human urine as part of the SDG, with contributions coming from both developed and developing nations.
A three-field plot analysis, linking authors, countries, and keywords, further supported these observations (Figure 1E). Sweden featured prominently, with leading researchers such as “Simha P”, “Vinnerås B”, and “Udert KM” contributing significantly to the field. The work of these authors was frequently associated with terms like “wastewater treatment”, “nutrient recycling”, “fertiliser”, and “source separation”, highlighting a shared research focus on the circular economy and nutrient recovery. Analysis of annual publication trends showed a steady increase in scientific output from 2015 onward, with the highest number of articles published in 2024 (Figure 1F). This upward trend underlines the growing importance of the topic in the context of environmental and resource management. However, a decline in 2025 publications may be attributed to a lag in database indexing or ongoing reporting of publications at the time of analysis. To bridge current research gaps, future studies should move beyond lab settings to field-based, interdisciplinary research across varied agroecological and socio-economic conditions. Emphasis is needed on decentralized urine management, affordable stabilization methods, and practical application strategies for smallholders and urban farmers. Advancing technological innovation will help transform human urine from a niche research topic into a mainstream tool for sustainable agriculture and nutrient circularity.
Properties and chemistry of human urine
Human urine is a valuable organic N source substitute for inorganic urea in agriculture. It contains 2,651 organic and inorganic compounds, including natural elements absorbed from food, air, or skin contact (25). Typically, urine contains 10–12 g L-1 of N, 0.1-0.5 g L-1 of P, and 1.0-2.0 g L-1 of K, along with secondary nutrients and micronutrients, though these levels vary by region (28). These concentrations mainly represent freshly excreted urine. However, nutrient forms and physicochemical properties can change considerably during storage due to urea hydrolysis and microbial activity. Under storage (e.g., sealed conditions for several months), urea is converted into ammonium, resulting in increased pH and potential ammonia volatilization if storage is not airtight (29). Nitrogenous substances in urine include ammonium salts, amino acids, ammonia, creatinine, urea, and uric acid (30), along with trace metals such as manganese, iron, zinc, and copper (29). Table 1 outlines the main components and properties of freshly collected urine and urine stored for 6 months.
Characteristics of fresh and stored human urine.
Parameter
Fresh human urine (mean)
Stored human urine (mean)
Mean ± SD*
Mean ± SD*
pH
5.9 ± 1.1
9.2 ± 0.3
TN
5463.8 ± 1597
5954.5 ± 289.2
TAN
416.5 ± 213.2
5840.7 ± 936.8
PO43-
343.7 ± 105.6
268.1 ± 103.8
Ca2+
89.6 ± 0.6
1.7 ± 0.2
Mg2+
54.8 ± 13.3
<50
Na+
2570 ± 664.7
2521.6 ± 1238.9
K+
1357.3 ± 342.1
1301.5 ± 309.1
Cl-
5535 ± 1534.4
3495 ± 1279.9
SO42-
865.5 ± 201.5
1202 ± 29.7
Unit - mg L-1 except for pH; TAN, Total ammoniacal nitrogen (NH3-N + NH4+-N).
Computed from the mean of listed reports (31, 32).
pH
Healthy human urine typically has a pH of around 6, though it can vary from 4.5 to 8 based on factors like diet and health (28). Women tend to have slightly higher urine pH than men, though the reasons are unclear, with limited research on female urine (25). The pH of stored urine increased compared to fresh urine due to hydrolysis in a non-sterile environment, which releases NH3 and CO2 from bicarbonate (33). In contrast, N fertilizers have varying pH levels depending on type. For instance, ammonium nitrate has a neutral pH of 5.5-7.5, while urea is slightly acidic with a pH of 5.0-6.5 (19).
Urea, the primary N source in urine, is hydrolyzed by urease, an enzyme found in plants, microbes, soil and the human body (34). Urea hydrolysis can occur either chemically or enzymatically. Enzymatic hydrolysis, driven by urease-producing bacteria from the human intestines and urinary system, typically occurs at temperatures between 37-50°C and pH 7-9 (35). In contrast, chemical hydrolysis occurs at 65°C and pH > 12.5 (29). During hydrolysis (reaction 3.1.1), one mole of urea breaks down into two moles of NH3 and one mole of carbonic acid (reaction 3.1.2), significantly altering urine composition. The pH affects the balance between NH3 and NH4+ (reaction 3.1.3), with higher pH promoting NH3 gas release (reaction 3.1.4). At a pH of around 9.3, over half of the NH3 in urine escapes as gas, causing the typical odor of hydrolyzed urine (36). Therefore, controlling urine pH during storage and processing is critical for fertilizer stabilization, as it directly influences ammonia volatilization losses and nitrogen retention in plant-available forms. Complete urea hydrolysis occurs within 72 hours, with pH playing a key role in NH3 or ammonium presence, impacting N recovery (33). It is generally understood that urea hydrolysis by urease occurs in four steps. The stepwise equations given by Mobley and Hausinger (37) are as follows:
CO (NH2)2(aq)+H2O(l)Urease (@25°C)→NH3 (aq)+NH2COOH(aq)→3.1.1NH2COOH(aq)+H2O(l)→NH3 (aq)+H2CO3(aq)→3.1.2NH3(aq)+H+pKa =9.25↔NH4+(4〈pH〉7)→3.1.3NH3(aq)↔ NH3(g)(7〈pH〉9.5)→3.1.4Electrical conductivity
Electrical conductivity (EC) measures the ionic strength of a solution and understanding urine conductivity is crucial for optimizing nutrient and energy recovery systems (38). EC does not directly correlate with ion concentrations in urine, as it is primarily influenced by sodium chloride and uric acid, while non-electrolytes, such as metabolic byproducts, have a lesser effect (39). Reported EC values for human urine in various studies include 28 ± 2 mS cm-1 (40), 28.1 mS cm-1 (41), and a range of 3.13-19.20 mS cm-1 (42). Hydrolyzed urine generally exhibits higher EC than fresh urine due to the increased production of ammonium ions during urea hydrolysis (18). Additionally, total dissolved solids such as calcium, magnesium, K, and P further affect urine composition, with diet and water quality influencing total dissolved solids levels (41).
From an agronomic perspective, high EC in urine may pose salinity risks when applied directly to soil, particularly under low rainfall conditions or in salt-sensitive crops. To mitigate this, urine is commonly diluted with water prior to application, which lowers ionic concentration and reduces osmotic stress in the root zone (39). Moreover, split applications combined with irrigation can minimize salt accumulation and improve nutrient uptake efficiency (43). Alternatively, stabilization and nutrient recovery technologies such as struvite precipitation, adsorption-based recovery and membrane-based separation can convert urine nutrients into concentrated solid fertilizers, thereby reducing direct salt loading in soils (44). Therefore, dilution and recovery-based stabilization strategies are essential to ensure safe field application of urine-derived fertilizers while avoiding salinity-related yield reductions.
Stabilization strategies in source-separated urine systems
Fresh urine typically becomes fully hydrolyzed into inorganic salts unless stabilized. Complete hydrolysis raises pH and NH3 concentration, facilitating nutrient recovery via struvite precipitation, ion exchange, electrochemical or biological treatment, and NH3 stripping (45). However, uncontrolled hydrolysis causes pipe scaling, blockages, NH3 emissions, air pollution, and N losses. Therefore, urine stabilization is essential to preserve urea-N, minimize emissions, and enable direct urea recovery. Urine stabilization can be achieved through acidification, alkalinization, electrochemical treatment, or urease inhibitors, each suppressing urease activity or urease-producing microorganisms. Effectiveness depends on pH, temperature, salinity, and free NH3, which influences both nutrient preservation and pathogen inactivation. To improve clarity and provide a practical overview, the major stabilization strategies are comparatively summarized in Table 2, emphasizing their mechanisms, advantages, limitations and scalability potential for decentralized and large-scale applications (46–49).
Comparative summary of human urine stabilization methods and their scalability potential.
Stabilization method
Principle/mechanism
Key advantages
Major limitations
Scalability potential
Storage (natural hydrolysis)
Urea hydrolysis increases pH and converts urea to NH4+
Simple, low-cost, pathogen reduction over time
NH3 volatilization, odor, N losses if not sealed
High (household/community scale)
Acidification
pH reduction (<6) inhibits urease activity and NH3 release
High N retention, reduces odor, improves stability
Acid requirement, handling risks, cost
Medium-High
Alkalinization
pH increase (>11) inhibits microbial activity and improves hygiene
Pathogen inactivation, stabilization
High chemical input, scaling challenges
Medium
Pasteurization/thermal treatment
Heating (≥70°C) kills pathogens and reduces microbial activity
Effective sanitation, rapid stabilization
Energy-intensive, infrastructure required
Medium
Struvite precipitation
Mg addition precipitates MgNH4PO4·6H2O
Recovers P and some N, solid fertilizer product
Requires Mg source, incomplete N recovery
High (commercially feasible)
Ammonia stripping/absorption
Converts NH4+ to NH3 gas and captures as ammonium salt
High N recovery, concentrated product
Equipment needs, operational control required
High (industrial scale)
Ion exchange/adsorption (biochar/zeolite)
NH4+ adsorption onto sorbent materials
Low-tech, reusable adsorbents, decentralized use
Sorbent regeneration, variable performance
Medium-High
Membrane concentration (RO/FO/ED)
Separation of nutrients via selective membranes
Produces nutrient-rich concentrate, high recovery
Membrane fouling, energy cost
Medium-High
Acidification
Acidification is the most studied approach, which lowers urine pH below 5, inhibits urease, and preserves urea-N (46), with sulfuric acid able to suppress activity for up to 100 days (50). Boncz et al. (46) recommend 60 mEq H+ L-1 (3 g L-1 concentrated H2SO4) for hydrolysis prevention over three months, with larger volumes of weaker acids required for the same effect. However, large-scale acid dosing increases operational costs, requires pumps, poses safety risks for untrained users, and complicates bulk transport logistics (51). To reduce sulphate accumulation from H2SO4, alternative stabilizers such as phosphoric, hydrochloric, and nitric acids have been evaluated, with phosphoric acid identified as the safest option when doses are optimized to prevent mineral precipitation (52). Saetta and Boyer (53) showed that 2.5 mL of 2,500 meq L-1 acetic acid per urination in anhydrous urinals effectively suppressed hydrolysis.
Ray et al. (54) ranked urease inhibitors’ effectiveness as citric acid > acetic acid > vinegar > sulfuric acid > ionic silver > ionic zinc > sodium fluoride, with organic acids effective at 3.2 x 101 - 1.6 x 102 meq L-1. Pre-acidifying urine was more effective than post-hydrolysis addition. Acid inhibition of urease is reversible and pH-dependent, so maintaining low pH through regular dosing especially before the first morning urination effectively stabilizes urine. Acidification also improves hygiene by reducing microbial survival, limiting pathogen transmission, and partially lowering organic carbon, suppressing odor (55). However, repeated long-term field application of acidified urine may contribute to gradual soil acidification, particularly in low-buffering sandy soils or already acidic soils, potentially affecting microbial activity, nutrient availability and overall soil health. Therefore, site-specific application rates, periodic soil pH monitoring and corrective measures such as liming or integration with alkaline amendments are recommended to sustain soil fertility and avoid long-term acidification effects (56). Lactic fermentation provides a biological alternative, lowering urine pH below 5 via degradable organic matter and lactic acid-producing bacteria (36), making it practical for decentralized and low-resource systems.
Alkalinization
Alkalinization is an effective urine stabilization strategy, raising pH to 11–13 to inhibit urease activity and inactivate urease-producing microorganisms (47). Lime-based stabilization with calcium hydroxide, often combined with biochar or wood ash, enhances alkalinity (57). Urease is effectively inhibited at pH >10 or temperatures >80°C (58), and non-enzymatic OH–catalyzed urea degradation remains 1,010 times slower than enzymatic hydrolysis (59). Calcium hydroxide effectively stabilizes urine for at least one month across a temperature range of 14 - 40°C, with a pH of 11 found to be optimal for this process. A dosage of 10 g L-1 provides a robust margin of stability, which is equivalent to 5 kg per capita per year (51). Wood ash can stabilize urine at 5-10% (w/w), requiring 25–55 kg per capita annually (60). Calcium hydroxide, when added at a 10 g L-1 (costing 0.8 cents L-1), is more cost-effective than magnesium salts. However, these cost estimates are primarily based on chemical input requirements and do not fully account for additional costs associated with decentralized implementation, such as labor for dosing and mixing, transport and storage logistics, infrastructure needs and safety considerations for handling alkaline materials. Combining alkalinization with volume reduction via reverse osmosis enhances nutrient recovery (26). Alkalized urine concentrated with wood ash or biochar at 35-65°C can yield fertilizer with 7.8% N, 2.5% P, and 10.9% K (59).
Chemical oxidation
Beyond pH control, chemical oxidation has been investigated as a stabilization approach. Hydrogen peroxide and heat-activated peroxydisulfate irreversibly inactivate urease by oxidative destruction of the enzyme (61) and these oxidants are widely used in water disinfection systems (62). However, oxidation leads to N losses via conversion of ammonium to N2 gas (61), making this method unsuitable when nutrient recovery is the primary goal.
Nitrification
Biological nitrification offers an effective stabilization pathway for hydrolyzed urine by oxidizing ammonium to nitrite or nitrate, lowering pH to 5–7 and suppressing ammonia volatilization and phosphate precipitation (48). This produces stabilized liquid fertilizer or, with distillation, a concentrated solid product (63). Complete nitrification can be achieved with controlled base addition (NaOH or Na2CO3) (48). Aerobic nitrification enhances heterotrophic microbial growth, degrading 90% of urine organic matter, reducing odor, and improving downstream treatments such as activated carbon adsorption for pharmaceuticals (63).
Electrochemical stabilization offers a rapid alternative for decentralized systems. In-situ chlorine generation using PtIr/Pt electrodes inactivates urease at >240 mV, preventing urea hydrolysis, producing treated urine suitable for flushing, with electricity costs lower than daily water expenses (64). De Paepe et al. (65) developed an electrochemical precipitation system where cathodic hydroxide generation replaces external alkali, reducing chemical use and environmental impact. Electrochemically stabilized urine fed into nitrification reactors allows current-controlled pH, enabling complete nitrification and nutrient concentration (66). With increasing renewable electricity, electrochemical stabilization with an optimal pH of 11 is a sustainable, scalable alternative to chemical alkalinization.
Urease inhibitors
Urease inhibitors have been studied at the molecular level but are limited in practical urine stabilization. They include hydroxamic acid derivatives, bisphosphoric amides, thiolic/heterocyclic compounds, and metal ions that block urease catalysis (49). Strongest inhibition is by silver and mercury, followed by Cu, Ni, Cd, Zn, and Co. Fluoride targets urease nickel centers (54). Natural inhibitors from garlic, onion, and Brassica juices also suppress urease via thiosulfites (67). Among synthetic urease inhibitors, NBPT is most effective under aerobic conditions, while PPDA performs better in waterlogged environments (68). Biochar also suppresses urease via surface-mediated reactions (69). Toxicity and variable efficiency limit large-scale use. Urine stabilization is a key part of source-separation and nutrient recycling, with method choice dependent on collection, fertilizer form, pathogen control, and environmental trade-offs. Acidification and alkalinization are most established, while electrochemical and biological approaches offer promising low-input options for decentralized systems.
Nutrient recovery from human urine: ways and means
Urine consists of approximately 95% water by weight, and reducing its volume offers a long-term solution for reuse (70). Though urine makes up only 1% of residential wastewater, volume reduction is crucial because its nutrient concentration is much lower than that of typical mineral fertilizers, making direct handling and application less practical. From an implementation perspective, concentrating urine not only improves nutrient recovery efficiency but also reduces storage and transport requirements, which are major logistical constraints for decentralized sanitation systems. Volume reduction decreases the bulkiness of urine-based fertilizers, lowers transportation costs and facilitates packaging and distribution, thereby improving farmer acceptance and adoption by enabling easier handling and field application using conventional equipment (71). Urine reuse can help address sanitation, hygiene, and food security in a closed-loop nutrient cycle, though these systems remain underdeveloped (72). Energy consumption depends on the complexity of the urine treatment process. Harder et al. (23) explored two methods: inhibiting urea hydrolysis to remove micropollutants and reducing urine volume for selective nutrient extraction. Both highlight the importance of volume reduction, which concentrates nutrients and enhances the value of urine-derived fertilizers. Nutrient recovery technologies aim to maximize nutrient recovery from urine while minimizing costs, enhancing their potential as a sustainable fertilizer (72). Innovative methods to recover N, P, and K, supporting sustainable agriculture and reducing environmental impact (Figure 2).
Various technologies for the recovery of nitrogen and phosphorous based components from human urine [adapted from Pathy et al. (71)].
Flowchart outlining nutrient recovery techniques divided into physical, biological, and chemical processes, with each method’s efficiency percentages and color codes indicating suitability for nitrogen, phosphorus, or both, explained in the legend at the bottom.Membrane separation technologyReverse osmosis
Reverse osmosis (RO) is a pressure-driven membrane separation process that reduces urine volume by applying pressure higher than the osmotic pressure, allowing water to pass through a semi-permeable membrane while retaining salts (73). This process effectively concentrates urine nutrients, particularly N, by allowing low N rejection while retaining salts and impurities. However, membrane fouling is a key limitation, decreasing flux and raising operational costs. Pre-treatment is essential to extend membrane life and performance (74). Courtney and Randall (73) found that calcium-stabilized urine requires pre-treatment to avoid scaling. They proposed three options, viz., air bubbling, sodium bicarbonate, and ammonium bicarbonate. While citric acid improved nutrient recovery, it also led to organic fouling, reducing permeate flow. Therefore, air bubbling is the preferred pre-treatment for calcium-stabilized urine in RO systems. Similarly, Ek et al. (75) used a 0.5 mm sieve, a 5 μm cartridge filter, and ultrafiltration as pre-treatment for RO, employing PCI AFC99 tube membranes and Filmtec SW30-HR spiral membranes. At pH 6, with 5 Pa pressure and 29°C, over 95% of N and P were concentrated. The process required 8 kWh per liter of urine, with chemical dosing crucial to prevent scaling.
Forward osmosis
Forward osmosis (FO) is a cost-effective alternative to RO for extracting N and P from urine, converting them into fertilizers (76). FO operates on a chemical potential gradient, where water moves from high to low potential across a membrane. Common FO membranes include cellulose triacetate (CTA) and thin-film composite (TFC) (77). FO reduces urine volume while concentrating nutrients, making it promising for water and nutrient recovery. Volpin et al. (78) achieved 60% urine concentration, recovering 40% P and 50% N using polyamide FO membranes. Liu et al. (79) used a CTA-FO membrane and recovered ammonium nitrogen (NH4+-N) by nearly 100%, though it reduced water flux. Ammonium’s larger hydrodynamic size makes it less likely to diffuse through the membrane than ammonia nitrogen (80). Volpin et al. (76) found similar FO performance for fresh and stored urine, with water fluxes of 22.5 L m-2 h-1 and 19.5 L m-2 h-1, respectively, using 2M NaCl as the draw agent. The slight difference was due to increased osmolality from urea hydrolysis. While FO is low-cost and robust, it is less effective for N retention, with a 10% difference in NH3 recovery noted (78). Despite the energy required for draw agent regeneration, FO remains an environmentally friendly and cost-effective method, achieving N, P, and K recovery rates of 95%, 97%, and 80%, respectively (81).
Nano filtration
Nanofiltration (NF) membranes can reject molecules ranging from 1–10 nm with pore sizes of 1–5 nm (82). Due to their high flux rates and lower energy consumption, many wastewater treatment technologies have shifted to NF systems (83). NF operates at much lower pressures than RO, reducing energy requirements for wastewater treatment (84). Pronk et al. (85) assessed NF’s performance using source-separated and synthetic urine, focusing on removing micropollutants like ibuprofen, diclofenac, carbamazepine, ethinylestradiol, and propanol, crucial for ensuring safe fertilizer production. Their study showed that the NF270 membrane, operated at 20 bar, achieved significantly higher rejection rates for these micropollutants compared to DS5 and N30F membranes. While NH3 and urea permeated effectively, phosphates and micropollutants were retained. The energy required for NF to treat 1 L of urine was 6 kWh, notably lower than RO’s energy consumption (86).
Membrane distillation
Membrane distillation (MD) is a thermally driven separation process that uses a temperature gradient to vaporize water, relying on the vapor pressure difference between high and low temperatures. A hydrophobic membrane permits only vapor molecules to pass through (87). Tun et al. (88) demonstrated nutrient concentration and water separation using PTFE (Polytetrafluoroethylene)/PP (Polypropylene) and PVDF (Polyvinylidene fluoride) membranes, with the PTFE/PP membrane achieving the highest water flux of 60 L m-2 h-1 at 70°C. However, higher temperatures increase NH3 transfer through the membrane. To reduce NH3 loss during MD, urine acidification is essential (88). Khumalo et al. (89) used a PVDF/PTFE/MfSNPs (methyl-functionalized nanoparticles) hybrid membrane, achieving high rejection rates for NH3 (>95%), sodium (>98%), and K (>89%), with 80% water recovery at pH of 10.5 and a 30 °C gradient.
Xu et al. (90) reported over 97% rejection of P and K using a hollow fiber PP membrane, though flux was limited to 3.57–4.96 L m-2 h-1. Zhao et al. (87) demonstrated that vacuum membrane distillation can effectively reject organic and inorganic solutes from urine, achieving 99.3-99.5% chemical oxygen demand (COD) and 40.6–75.2% NH3 rejection. Integrating MD with reverse electro dialysis (MD-RED) offers a potential solution for nutrient and energy recovery. For example, Mercer et al. (91) demonstrated that this hybrid system can generate 0.2 W m-2 of power, sufficient to operate sweep gas fans and micro pumps. Pre-treating urine is crucial for extending membrane life in MD processes, as without it, micropollutants may adhere to the membrane surface, clog pores, decrease permeate flux, and reduce water quality (89). MD is unsuitable for stabilized urine due to the risk of chemical urea hydrolysis from the required temperature gradient. MD’s energy demands, ranging from 100 to 240 kWh m-3 (92), are lower than conventional evaporation processes (1320 kWh m-3) (57).
Microbial fuel cell (MFC) technology, commonly used in wastewater treatment, shows potential for nutrient recovery, though most research focuses on energy production (93). In MFC, bacteria convert organic matter into electricity, with urine serving as an ideal substrate due to its high conductivity and buffering capacity (carbonate and bicarbonate). MFCs offer a sustainable approach for recovering ammonium and generating energy from urine (94). During urea hydrolysis in urine, ammonium transfers through the cation exchange membrane to the cathode, where it converts to volatile ammonia due to increased pH (93). This process enables the simultaneous recovery of up to 3.29 g d-1 m-2 ammonium and 3.46 kJ g-1 energy (95). Santoro et al. (96) operated a single-chamber MFC with urine for 45 days, noting 75% COD reduction and struvite formation on the cathode, which hindered power production.
Microbial electrolysis cell
The architecture of MFCs and microbial electrolysis cells (MECs) is similar, with the primary difference being the cathode environment (93). In MFCs, the anode is anaerobic while the cathode is aerobic; in contrast, both chambers of MECs are anaerobic. Without a terminal electron acceptor, water at the MEC cathode is reduced to hydrogen and hydroxyl ions (97). The hydroxyl ions raise the cathode pH, converting ammonium into volatile NH3, which helps balance pH in both chambers (95). Unlike MFCs, MECs do not require aeration. They can recover ammonium and generate energy as hydrogen gas (94). An additional voltage of 0.5-1.0 V is necessary in MECs to overcome thermodynamic limitations for hydrogen production, enhancing ammonium ion migration from anode to cathode and improving recovery efficiency (97).
Ledezma et al. (30) found that ammonium transfer in MECs exceeded that in MFCs, with a maximum removal rate of 519.5 g m-3 d-1 and a 141% transfer through the membrane. Stacking anion exchange membranes (AEM) and cation exchange membranes (CEM) in MECs enhances ion transport, improving treatment efficiency for diluted human urine. This nutrient separation MEC can concentrate phosphate and ammonium by factors of 3.0 and 4.5, respectively (93). While ion exchange membranes are effective, their high cost can be a barrier. Fortunately, terracotta and ceramic offer promising and low-cost alternatives that can be synthesized for similar applications. Ledezma et al. (30) achieved reconcentration rates of 7.2 kg NH4+-N, 0.5 kg PO4-P, and 1.6 kg K+ per m3 per day using a single pair of AEM and CEM.
Electrodialysis
In electrodialysis (ED), CEM and AEM are positioned between the anode and cathode, allowing cations and anions to migrate based on the applied charge (98). This facilitates the separation of pharmaceuticals and nutrient concentration from urine. ED effectively removes micropollutants, achieving complete rejection of ethinylestradiol (99). Wang et al. (100) combined a membrane bioreactor with electrodialysis, creating an electrodialysis membrane bioreactor (EDMBR) that used voltage generated from urine for ED, achieving removal rates of 94.5% for sulphate, 76.7% for phosphate, and 97.4% for ammonium. Kedwell et al. (80) utilized selective ED to recover 72% ammonium and 90% phosphate within 3 hours using various exchange membranes. De Paepe et al. (101) reported 80-85% water removal from nitrified urine but noted losses of up to 30% N and 60% P. Energy requirements vary widely, with reports ranging from 4.3 to 103 kWh m3 for N recovery (102).
Ion exchange and adsorption
Natural zeolites and resins are commonly used to recover ammoniacal nitrogen from urine, with efficiency varying by material. Zeolites, ranked by cation affinity, adsorb both ammonium and K at similar levels (103). In an up-flow packed bed reactor, clinoptilolite achieved 100% ammonium adsorption under optimal conditions, with 94% ammonium and 99% K at an initial loading of 10 mg NH4+ g-1 of clinoptilolite (104). Hybrid anion exchange resins, combining hydrated ferric oxide nanoparticles with anion exchange resin, adsorb up to 97% phosphate from urine in under 5 minutes (105). Guan et al. (106) used zirconia-coated magnetic nanoparticles for P recovery from urine at pH 4, achieving over 97.5% phosphate stripping with 1M NaOH. Kini and Hari (107) demonstrated that ground granulated blast furnace slag (GGBS) adsorbed over 90% phosphate from 50% diluted urine using 700 g L-1 of GGBS. Regenerating exhausted adsorbents is crucial for nutrient recovery via ion exchange and adsorption (103).
Biochar as an absorbent for recovery
Biochar is derived from sources like food waste, agricultural residues, and sewage through biomass carbonization in low-oxygen conditions (108). Its large surface area, multifunctional groups, and high carbon content make it environmentally friendly (109). Larger surface areas enhance biochar’s ability to adsorb chemicals, while its negative surface charge promotes ammonium adsorption through electrostatic interactions (108). Biochar’s COO-, OH-, CO, and -OH groups facilitate N and P adsorption through ion exchange (11). Electrostatic forces aid in the exchange of NH4+ with H+ and PO43-/NO3- with OH-.
Engineering approaches, such as adding metal oxides, have increased biochar’s phosphate adsorption capacity from human urine (90). Modified biochar, with enhanced surface area and electron transfer capacity, improves adsorption and kinetics (110). For instance, MgO-modified biochar shows superior phosphate adsorption (111), while dolomite-modified biochar offers phosphate binding at low pH (112). ZnCl2-activated biochar improves P adsorption by expanding pores and creating positive surface sites (113). Xu et al. (110) showed magnesium-oxide-modified biochar recovered 47.5 mg N g-1 and 116.4 mg P g-1 from human urine, making it a nutrient-rich fertilizer. Similarly, Zhang et al. (114) demonstrated that magnesium-functionalized Magnolia grandiflora leaf biochar effectively recovers P from urine, with excellent adsorption and slow-release properties.
Otieno et al. (115) used pineapple peel biochar (PPB) and lateritic soil (LS) to adsorb ammonium nitrogen (NH4+-N) from urine. The D-R isotherm model best describes NH4+-N adsorption, indicating physical adsorption, with PPB and LS having surface adsorption energies of 1.826 x 10–2 and 1.622 x 10–2 kJ mol-1, respectively. PPB exhibited higher NH4+-N adsorption (13.40 mg g-1) than LS (10.73 mg g-1), attributed to its larger surface area and porosity. Combining biochar with struvite precipitation boosts N and P recovery from urine by 40%-50% and 99%, respectively, making modified biochar more effective than pristine biochar (31).
Miscellaneous technologyEvaporation
Evaporation converts the water in urine into vapor, which can be condensed and recovered as pure water, leaving behind a nutrient-rich concentrated liquid for fertilizer. This method effectively reduces urine volume while conserving nutrients, addressing transportation issues (20). However, N loss due to NH3 volatilization is a key limitation, which can be mitigated by using H2SO4 to form ammonium sulfate or stabilizing the urine (116). While urine’s high boiling point of 130°C allows for efficient water removal with minimal nutrient loss, energy costs for conventional evaporation methods remain high (86). Dutta and Vinnerås (117) achieved 74% N recovery from urine dried with ash and calcium hydroxide at 35°C. Senecal and Vinnerås (59) used wood ash to evaporate fresh urine at 35°C and 65°C, reducing volume by 95% and yielding a concentrated solution with 7.8% N, 2.5% P, and 10.9% K, comparable to commercial fertilizers.
Vasiljev et al. (118) dried fresh urine by incorporating magnesium-doped alkaline substrates, achieving a complete nutrient recovery at 38°C. Antonini et al. (119) employed low-cost solar thermal techniques, producing 360 grams of solid fertilizer from 50 L of undiluted urine in 26 days. Acid (acetic acid) and base (calcium hydroxide) stabilization of fresh urine before evaporation improved N recovery to 100% and 98%, respectively (116). Increasing temperatures from 35 to 65°C decreased N recovery from 90% to 66%, with recovery dropping to just 30% at 90°C (57). Research indicates that 35-40°C is optimal for urea conservation in evaporation-based fertilizer production (51).
Freezing
Freeze concentration (FC) involves freezing an aqueous salt solution, forming ice crystals that exclude non-water particles and leaving behind a concentrated solution (120). Eutectic freeze concentration (EFC) enhances this by causing salts to crystallize alongside ice at the eutectic point, when the solution is fully saturated (121). These freeze processes are more energy-efficient than evaporation, as the latent heat of fusion is six times lower than that of vaporization (47) and they prevent chemical urea hydrolysis (57). Noe-Hays et al. (122) achieved 92% nutrient recovery and 83% water removal using a two-stage block freeze concentration process.
Moharramzadeh et al. (47) employed progressive freeze crystallization to concentrate stabilized urine, recovering 59% of the urea while removing 80% of the water. Randall and Nathoo (121) predicted that at -27°C, EFC could recover 90% of N from hydrolyzed urine as ammonium chloride and ammonium bicarbonate. Although EFC has only been theoretically studied for urine, it has effectively been used in water treatment and salt recovery from various waste streams, including seawater desalination and textile wastewater (120). EFC offers advantages over traditional freeze concentration by using gravity to separate salts and ice, enabling sequential removal based on eutectic temperatures (47).
Struvite precipitation
Struvite precipitation is a simple method for recovering P and N from urine as struvite crystals, composed of phosphate, magnesium, and ammonium (44). This process occurs as urine’s pH rises due to urea hydrolysis, forming ammonium. Struvite forms in stirred or baffled reactors and is then filtered, dried, and collected (70). While magnesium sources like MgO, MgSO4, and MgCl2 are used to facilitate struvite formation, MgO is the most economical source. However, ammonium recovery through struvite is less than 10%, limiting its effectiveness as a fertilizer (44). N recovery required 11 kWh kg-1 at 30°C and 8 kWh kg-1 at 20°C (51).
Technology summary
A review of nutrient recovery technologies shows that energy consumption for fertilizer production is based on the urea content in 1 m3 of urine. A summary of technologies for the recovery of nutrients from human urine and its recovery efficiencies were depicted in Figure 3. P and K recovery is generally high due to their non-volatile nature, making membrane methods effective. N recovery varies depending on urine hydrolysis, stabilization, and pH. While most technologies remove over 70% of water, only evaporative processes achieve complete removal, but at more than twice the energy demand of synthetic urea production. FO has lower energy needs, though draw solution recovery remains a challenge (24). RO retains at least 80% of N, compared to 50% with FO (78). However, hydrophobic gas separation is better suited for hydrolyzed urine, where N is retained as ammonium. Energy requirements for ED vary widely, complicating its assessment, particularly for stabilized urine. Freeze concentration has the second-lowest energy requirements, while RO requires the least. RO effectively removes most water from urine but may face scaling issues, and combining methods can improve energy efficiency (73). Additionally, nutrient recovery processes must address micropollutants like pharmaceuticals to ensure fertilizer safety (123). Table 3 outlines the diverse technological approaches for nutrient removal from human urine, along with their benefits and challenges.
Summary of technologies for recovery of nutrients from human urine [adapted from Courtney and Randall (120); Patel et al. (72)]. (A) Source separation, stabilization and pre-treatment, (B) Membrane separation and bio-electrochemical, and (C) Miscellaneous technologies for nutrient recovery from human urine and (D) Nutrient recovery efficiencies of urine-recycling technologies.
Four-panel infographic showing urine treatment technologies. Panel a illustrates source separation and stabilization using chemical additives and filtration. Panel b compares membrane separation technologies like forward osmosis, distillation, nanofiltration, reverse osmosis, and bio-electrochemical cells including microbial fuel cells and electrodialysis. Panel c highlights miscellaneous methods: ion exchange, biochar adsorption, struvite precipitation, evaporation, and eutectic freeze concentration, each with labeled diagrams. Panel d presents a horizontal bar chart comparing recovery efficiencies of various technologies for nitrogen, phosphorus, and potassium as percentages, with colored segments representing N, P, and K recovery.
Nutrient retrieval from human urine across diverse technological approaches.
Technologies
Urine type used
Nutrient recovery efficiency
Energy requirements (kWh m-3)
Water removed (%)
Pathogens in products
Process stability
Extent of bioavailability for plant uptake
Effect of long-term application of recovered products on soil and crops health
Advantages
Limitations
References
Reverse-Osmosis (RO)
Real urine-dilute-hydrolyzed
NH4 - 70%,PO34- - 73%,K - 71%
3-5
80
–
Pressure and pH sensitive
High
Salt build-up in soil, increased water stress, build-up of contaminants in soil and uptake by plants
High efficiency in water removal and nutrient recovery.
High operational and maintenance costs.
Osipi et al. (74)
Forward-Osmosis (FO)
Real urine
N - 75%,P - 85%,K - 90%
0.3-0.8
80
High
Highly pH sensitive
High
Salt build-up in soil, toxic to plants, organic contaminants soil and uptake by plants
Lower energy consumption compared to reverse osmosis.
Effective for divalent ions and moderate operational cost.
Membrane fouling issues.
Patel et al. (72)
Membrane-distillation
Real urine-hydrolyzed
N - 95%,P - 98%,K - 97%
3-6
99
Low
Temperature sensitive
High
Salt build-up in soil, accumulation of pathogens and organic contaminants in soil and uptake by plants
High recovery rates for multiple nutrients.
High operational costs.
Khumalo et al. (89)
Electrodialysis (ED)
Nitrified – diluted
N - 70%,P - 40%,K - 71%
1.5-2.5
80
High
pH sensitive
High
Relatively safe
Versatile for multiple nutrient recovery.
High energy consumption.
De Paepe et al. (101)
Microbial electrolysis cell-ED
Synthetic, hydrolyzed
N - 50%,P - 43%,K - 55%
0.6-1.0
30-50
High
pH sensitive
Medium
Limited due to inconsistent nutrient recovery.
Reduced energy costs.
Costly and complex setup.
Kuntke et al. (97)
Electrolysis cell-ED
Synthetic, hydrolyzed
N - 72%,P - 39%,K - 79%
–
80
High
pH sensitive
Medium
Stable with proper input; contaminants affect crops.
Simultaneous nutrient and energy recovery
High operational complexity, requires stable input
Tun et al. (88)
Ion-exchange
Stabilized urine
N - 80%,P - 75%,K - 70%
0.5-1.5
–
High
Relatively stable
High
The build-up of organic pollutants in the environment
Selective recovery of specific ions.
Resin regeneration and disposal concerns.
Huang et al. (125)
Adsorption
Real urine
NH4–18 mg g-1PO4–50 mg/g
–
–
High
Stable
High
Relatively safe
Low energy consumption, easy operation
Adsorbent regeneration or replacement required
Tong et al. (126)
Biochar
Real urine
NH4+ - N - 13.40 mg g-1
–
–
Time and pH dependent
Stable
High
Safe application, minimal adverse effects on soil and crops health.
Affordable, effective in binding nutrients
Limited nutrient recovery, dependent on biochar quality
Otieno et al. (115)
Evaporation method
Real urine-hydrolyzed
N - 97%P - 96%
–
95-99
Low
Highly unstable with temp and pH shift
High
Sodification of soil,increased water stress,accumulation ofcontaminants in soiland uptake by plants
High nutrient concentration
High energy cost, risk of ammonia volatilization
Riechmann et al. (116)
Block freeze concentration
Hydrolyzed real urine
92% nutrient recovered
0.4-0.7
80-95
High
Temp sensitive
High
High nutrient retention. Complex operation affects stability in large-scale use.
High nutrient retention.
Complex operation.
Noe-Hays et al. (122)
Progressive freeze concentration
Stabilized synthetic urine
59% urea recovery
0.4-0.7
85-95
High
Temp sensitive
High
Suitable for moderate recovery of nitrogen-based fertilizers but less efficient for other nutrients.
Effective for urea recovery.
Lower efficiency for other nutrients.
Moharramzadeh et al. (47)
Eutectic freeze crystallization
Stabilized synthetic urine
Urea - 77%,K - 96%
0.5-0.8
95-99
High
–
High
Soil sodification, accumulation of pathogens and organic contaminants soil and uptake by plants
Effective N recovery in solid form.
High operational complexity.
Courtney and Randall (120)
Struvite precipitation
Hydrolyzed real urine
Allows fractional nutrient recovery
–
–
High Improvements: Pathogen removal by washing or drying of precipitate
Sensitive to Mg: PO4 ratio and pH
Struvite is a slow-releasing fertilizer
Accumulation of pathogens in the soil
Simple process, recovers phosphorus effectively
Limited recovery of other nutrients
Lorick et al. (127)
CaP/AlP precipitation
Real urine
P - 80-99%NO3- - 83.3 mg/g
–
–
Increased medium pH inactivates pathogens present
Relatively stable
Al-bound P is not readily available for plant uptake, while CaP acts as a releasing fertilizer.
Al and Ca build up in soil, leading to soil and plant toxicity
Phosphorus recovery, low cost
Limited nitrogen recovery
Saliu and Oladoja (128)
Ammonia stripping technique
Stabilized [Ca (OH)2]
P - 99%NH4-N - 85-99%
–
96
Low
Highly pH sensitive
High
Safe
Environmentally friendly and cost-effective.
Vulnerable to pollution.
Lorick et al. (127)
Solar distillation
Hydrolyzed then acidified
50% NH3 recovered as NO3-
0.1-0.3
100
Low
Gravity operates mainly
Medium
Safe in long-term application. Slight soil degradation over time.
Simple and cost-effective
Dependent on sunlight availability.
Ren et al. (129)
Thermal
Stabilized (wood ash)
N - 93%,P - 97%,K - 99%
3-5
80
–
Temp sensitive
High
Long-term safety depends on repeated use and absence of contaminant residues.
High efficiency in nutrient recovery.
High energy demand.
Lyu et al. (130)
Distillation and nitrification
Hydrolyzed and nitrified urine
50% NH3 recovered as NO3-
2-4
95-99
High
pH sensitive
Medium
Properly controlled, minimal contamination issues with long-term use.
Effective nitrogen conversion.
High energy demands.
Udert and Wächter (131)
Bio-electrochemical system
Synthetic, hydrolyzed
NH4+ Nm-2 d-1–162 gP - 90%
–
50-70
–
High temp sensitive
High
Relatively safe
Decreased energy costs by eliminating aeration.
Costly
Sharma and Mutnuri (132)
Influence of human urine-based fertilizers on arable crop productionImpact on crop growth and yield
Crop yield is the primary measure of fertilizer performance and urine-derived fertilizers can match or exceed synthetic N fertilizers when applied at equivalent rates and managed to reduce losses (133). In cereals and vegetables, nitrified or stabilized urine generally performs comparably to urea, with incorporation or acidification enhancing effectiveness, though odor and public perception may limit vegetable adoption (134, 135). While human urine provides rapidly available urea-N and exhibits high NUE, its performance contrasts with other circular fertilizers commonly used in sustainable nutrient management (17). These amendments release nutrients more slowly because their N is bound in organic matter and must undergo microbial mineralization, which cannot be matched by urine’s immediate N supply.
However, agronomic performance of urine-derived fertilizers is not uniform and may vary across soil types and climatic conditions. In sandy soils with low cation exchange capacity, urine-derived nitrate and potassium are more prone to leaching losses, particularly under high rainfall or excessive irrigation, which may reduce nutrient recovery and crop response. In contrast, clay-rich soils generally retain ammonium and potassium more effectively, improving nutrient availability and fertilizer efficiency (22). Soil pH also strongly influences ammonia volatilization, as alkaline soils favor NH3 loss from hydrolyzed urine, whereas acidic soils may reduce volatilization but require careful nutrient balancing under repeated application (39). Furthermore, climatic factors such as temperature and moisture regulate urea hydrolysis, microbial nitrification and ammonia emissions, making stabilization strategies and application timing critical in hot-humid tropical regions and arid environments (45). Therefore, optimizing dilution, stabilization method, placement and timing based on local agroecological conditions is essential to maximize yield benefits and minimize environmental risks.
Compost and well-aged manure contain mainly organic N requiring microbial mineralization, offering slow-release benefits for perennial or long-season crops but often insufficient for peak demand in high-yield systems (136). Digestate, with 50-70% ammonium N, provides faster availability than raw organic inputs, though its effectiveness depends on feedstock, storage, and solid-liquid separation, and surface application without incorporation poses volatilization risks (137). Struvite is a low-solubility mineral fertilizer, provides slow, sustained N and P release, minimizing losses but often insufficient for peak crop demand, making it suitable as a basal or starter fertilizer (138).
Mixed recovered nutrient fertilizer formulations, such as compost plus struvite, provide flexible options to optimize yield and enhance soil health (139). Effective management of urine-derived fertilizers requires synchronizing N release with crop uptake by considering fertilizer chemistry, application method and soil-plant-microbe interactions. These comparisons show that while compost, manure and digestate contribute important soil-building benefits, properly stabilized urine alone or combined with organic amendments provides immediate nutrient availability and competitive yield performance, strengthening its role within circular and regenerative nutrient management systems.
Impact on seasonal crop
The use of human urine as a fertilizer has been shown to significantly enhance crop growth and yield, surpassing the performance of conventional synthetic fertilizers. Urine N, mainly in the form of urea or ammonium, enhances plant development, while P and K in plant-available forms further increase its fertilizer value (17). Srinivasamurthy et al. (140) found that a combination of human urine and FYM resulted in increased French bean yield to 4.9 t ha-1 compared to 2.6 t ha-1 with urine alone. In a fertigation study, Srinivasamurthy et al. (140) reported that tomato yields peaked at 26.75 t ha-1 using the recommended dose of N (RDF-N) from human urine, outperforming N from chemical fertilizers (15.3 t ha-1). Similarly, ashgourd yields were also highest with RDF-N from human urine and gypsum (39.2 t ha-1), compared to chemical fertilizers with FYM (36.7 t ha-1) and FYM alone (19.7 t ha-1) (140).
Sridevi et al. (141) reported that combining 40% RDF-N from FYM with 60% from human urine yielded the highest French bean production (4.9 t ha-1) compared to 100% RDF from chemical fertilizers (3.9 t ha-1). Here, N was applied through urine and FYM, while single super phosphate and muriate of potash provided P and K, respectively. FYM was used as a basal application, and urine was split into two doses before 50% flowering. The enhanced nutrient availability from urine improved N absorption and photosynthesis, leading to higher yields. This boost is linked to the high N and nutrient content in urine, which may enhance crop growth due to compounds like indole-3-acetic acid (IAA) in the urine (142).
Furthermore, Boh et al. (143) studied the effects of varying salinity levels (low, medium, high) on sorghum biomass yield with urine-derived fertilizers. Urine was collected from a students’ hostel at the University of Hohenheim, Germany, and stored for 12 months at 25 ± 2°C. To match the N in 1 liter of urine, ammonium nitrate was dissolved in deionized water. Results showed that soil enriched with 90 mg urine-N kg-1 (liquid form) increased sorghum biomass by 49% at low salinity, 34% at medium salinity, and 40% at high salinity, outperforming conventional ammonium nitrate-N. Similarly, larger N treatments (180 mg N kg-1 from urine-N and ammonium nitrate) under low and medium salinity increased sorghum biomass by 22% and 17%, respectively, compared to ammonium nitrate alone. In medium salinity, plants treated with 90 and 180 mg urine-N kg-1 had similar root and shoot biomass, though root biomass allocation increased by 20% with urine-N at 180 mg N kg-1. Under high salinity, urine-N reduced root biomass by 50%, while ammonium nitrate increased it by 44% (143). This reduction in biomass with high urinary N in saline soils occurs because salts compete with N ions for root uptake, limiting N assimilation (144). High urinary N intensifies osmotic stress, ion toxicity, and nutrient imbalances, further reducing biomass (143). Sodium ions disrupt NO3- and NH4+ transport, hindering plant growth. This interplay highlights the need for careful N management in saline soils to optimize yields.
In a study by Viskari et al. (145), urine samples were collected from male urinals at a music festival in Helsinki and from a household. Both batches were stored over winter in sealed containers. The results showed that the barley cv. Wolmari yielded 6.2 t ha-1 with urine-derived fertilizer, 6.8 t ha-1 with mineral fertilizer, and 4.5 t ha-1 without fertilization under a 54 kg N ha-1 treatment, supplemented with a chemical source to match urine N content. For the Harbinger variety, treatment with 100 kg N ha-1 fertilization yielded 7.6 t ha-1 for urine-derived fertilizer, 7.2 t ha-1 for mineral fertilizer, and 4.4 t ha-1 for without fertilization. Grain yields were consistent across cultivars and N rates, with increases of 60-70% compared to unfertilized conditions.
The application of urine-enriched biochar fertilizer (solid form) significantly increased cabbage weight by 361 g (1061 g vs. 700 g) and kohlrabi by 79 g (241 g vs. 163 g) compared to conventional fertilizer. Vegetable yield per plot rose by two-thirds, while yield per area increased by about 60% (p< 0.001). Cabbage output per square meter increased by 1.6 kg (4.25 kg vs. 2.65 kg), and kohlrabi by 0.8 kg (2.1 kg vs. 1.3 kg) (135). Similarly, maize treated with urine-enriched biochar produced 680 mg pot-1, an 8% increase over diammonium phosphate (110), demonstrating the potential of urine-based fertilizers, especially with biochar, to enhance crop yields and support sustainable agriculture.
Impact on perennial crop
Human urine is increasingly recognized as a sustainable fertilizer due to its nutrient-rich composition (144). Its high N content boosts soil N, promoting rapid vegetative growth, especially in N-demanding crops. Urine also provides readily available P, enhancing root development, particularly beneficial for root crops and fruiting plants (142). The K in urine strengthens plant cell walls, improving drought resistance and disease tolerance (117). Beler-Baykal et al. (146) evaluated clinoptilolite enriched with N from urine as a fertilizer for Ficus elástica. Urine samples were mixed, stored for six weeks to ensure complete urea conversion, and monitored for ammonium concentration, EC, and pH. Clinoptilolite was added to urine, with a blank sample used for comparison. Initial loading of 3 mg NH4+ g-1 clinoptilolite showed similar plant height increases across treatments in the first four weeks. However, after three months, the container treated with drained clinoptilolite exhibited a 34% growth rate, surpassing synthetic fertilizer (32%) and urine alone (19%).
Greenhouse study
In a greenhouse study by Akpan-Idiok et al. (147), okra plants treated with 15,000 L ha-1 (42 cm) and 20,000 L ha-1 (41.7 cm) of human urine were significantly (P< 0.05) taller than those treated with NPK 15:15:15 fertilizer (38.3 cm). Urine was applied to match N levels, with P and K supplied chemically. The 15,000 L ha-1 urine treatment (24.4 g plant-1) outperformed inorganic fertilizer (23.2 g plant-1) in the greenhouse, while 20,000 L ha-1 urine (34.7 g plant-1) produced higher yields than the NPK fertilizer (32.42 g plant-1) in the field experiment. Case studies show that urine-derived fertilizers positively impact a range of crops, including leafy greens, cereals, root crops, fruit-bearing plants, and legumes. To maximize benefits, proper dilution, safe application, and regular soil monitoring are crucial. When applied correctly, urine serves as a sustainable, cost-effective fertilizer that enhances productivity (148). Compared to livestock excreta, green manure, and composted FYM, urine releases nutrients more quickly (149). Despite its nutrient richness, urine faces challenges related to social acceptance, logistics, and soil impacts. Continued research and education are vital to optimizing urine’s role in sustainable agriculture. The comparative effectiveness of urine-based fertilizers relative to synthetic N sources is summarized in Table 4. Across crops such as amaranthus, cabbage, tomato, maize and spinach, urine consistently produced yields equal to or higher than those obtained with mineral fertilizers at equivalent N application rates. These results indicate that the nutrient availability and NUE of stabilized urine can reliably match conventional fertilizers, particularly in short-duration vegetables and cereals. Such evidence reinforces the agronomic potential of urine-derived fertilizers within integrated nutrient management systems.
Comparison of crop yield using urine and conventional fertilizers: a summary of studies.
Crop
Source and dosage
Yield
Plot type
Region
References
Amaranthus
Urine: 100 kg N ha-1
58.2 t ha-1
Field
Nigeria
AdeOluwa and Cofie (150)
Mineral: 100 kg N ha-1
34.3 t ha-1
Cabbage
Urine: 121 kg N ha-1
21.3 t ha-1
Seeded: greenhouse moved to field
Ghana
Amoah et al. (151)
Mineral: 121 kg N ha-1
21.1 t ha-1
Spinach
Urine: 200 kg N ha-1
162 g pot-1
Greenhouse: pot
South Africa
Kutu et al. (152)
Mineral: 200 kg N ha-1
150 g pot-1
Okra
Urine: 20,000 L ha-1
34.72 g plant-1
Greenhouse: pot
Nigeria
Akpan-Idiok et al. (147)
Mineral (RDF-N)
32.42 g plant-1
Potato
Urine: 49 kg N ha-1
300 g pot-1
Field
Nepal
Pradhan et al. (153)
Manure: 48 kg N ha-1
281 g pot-1
Mustard
Urine: 78 kg N ha-1
371 g pot-1
Manure: 73 kg N ha-1
131 g pot-1
French bean
Urine (RDF-N)
2.63 t ha-1
Field
India
Srinivasamurthy et al. (140)
Urine + FYM (RDF-N)
4.87 t ha-1
Ashgourd
Urine (RDF-N)
39.2 t ha-1
Fertilizer + FYM (RDF-N)
36.7 t ha-1
Barley (cv. wolmari)
Urine: 54 kg N ha-1
6.2 t ha-1
Field
Finland
Viskari et al. (145)
Mineral: 54 kg N ha-1
6.8 t ha-1
Barley (cv. Harbinger)
Urine: 100 kg N ha-1
7.6 t ha-1
Mineral: 100 kg N ha-1
7.2 t ha-1
Impact on cultivated soil propertiesSoil pH
The impact of human urine on soil pH depends on factors such as urine pH, application rate, frequency, and soil buffering capacity (39). Fresh urine typically has a pH between 6 and 7 (25). Larger and more frequent applications tend to have a greater effect on soil pH. Shingiro et al. (149) found that control soils had the highest pH (7.98), while soils treated with a 1:3 urine-to-water ratio had the lowest pH (6.56). Kassa et al. (154) reported no significant pH difference between the top and bottom layers of maize pot cultures from urine application, likely due to soil buffering capacity resisting rapid changes. Soil buffering capacity, which helps stabilize pH, plays a key role in mitigating pH shifts (149). Thus, the effect of urine on soil pH depends on several interacting factors, including soil type, application rate, and buffer capacity.
Soil EC
Urine application in agriculture can significantly alters soil EC due to its high ionic strength, mainly contributed by soluble salts such as sodium, chloride and ammonium (18). Soil salinity is commonly evaluated using the electrical conductivity of the saturated soil extract (ECe), where soils are generally classified as non-saline (<2 dS m-1), slightly saline (2–4 dS m-1), moderately saline (4–8 dS m-1), strongly saline (8–16 dS m-1) and very strongly saline (>16 dS m-1). Therefore, maintaining soil EC below 2 mS cm-1 and sodium adsorption ratios under 13 is recommended to minimize salinity and sodicity risks in cultivated soils (18). Excess Na and N residues can hinder nutrient absorption, reducing plant growth due to low K: Na ratios (42). Proper urine application management is crucial to prevent nutrient imbalances that hinder plant development (149). Application of urine had a higher EC (0.4 dS m-1) compared to 100% chemical fertilizers (0.1 dS m-1), emphasizing the need for balanced application and management to optimize soil health and crop growth (141).
In areas with soil salinization issues, urine’s high salt content requires cautious use as fertilizer. Boh et al. (143) reported increased soil salinity of 2.6, 3.6, and 5.3 dS m-1 with low, medium and high urine applications, indicating a shift from slightly saline to moderately saline conditions under higher application rates. Similarly, EC values of around 4.7 dS m-1 were reported under maize cultivation with urine fertilization (154). Alemayehu et al. (43) observed a 0.55 mS cm-1 rise in salinity after three split urine applications, while Sene et al. (18) found no salinity impact even under tripled urine treatments, suggesting that soil texture, drainage and climatic conditions strongly regulate salt accumulation.
Importantly, many EC increases observed after urine application may represent short-term effects, particularly immediately after fertilizer addition and can be reduced through rainfall, irrigation, crop uptake and leaching below the root zone (143). However, long-term soil degradation risks may occur when urine is repeatedly applied at high rates in poorly drained soils or arid and semi-arid climates where leaching is limited, potentially leading to gradual salt build-up and yield decline. To minimize crop damage and long-term salinity risks, urine should be diluted before application and applied in split doses with adequate irrigation management (43). Overall, despite the risk of increased EC under high application rates, urine-based fertilizers often remain within acceptable salinity thresholds and can match or exceed chemical fertilizer performance, while supporting plant growth when properly managed.
Soil chemical reactions
Human urine is a valuable N source, supplying essential nutrients in water-soluble forms that are readily absorbed by plants (155). The primary nitrogenous compounds in urine are urea, NH3, NH4+, and NO3-, making it an effective N fertilizer (28). This approach also helps close the nutrient cycle due to urine’s high nutrient concentration and easy application (154). Their long-term effects on nutrient content, microbial activity, pH, and fertility are essential for sustainable soil management (156). Sridevi et al. (141) found that applying 40% RDF-N via FYM basal + 60% human urine produced the highest soil available N (591.7 kg ha-1), P (55.3 kg ha-1), and K (505.1 kg ha-1), due to efficient nutrient release.
Sangare et al. (155) found that 100% urine application caused soil acidification (pH = 5.40) due to NH3 nitrification. However, mixing urine with toilet compost mitigated acidification. Alemayehu et al. (157) investigated the effects of human urine combined with coffee processing wastewater (UCPWW) on soil, finding minimal changes in pH (0.16 units) and total N (0.07 units) while increasing Na+ by 1.49, Cl- by 2.13, and salinity by 0.55 units. Soil treated with UCPWW at a 1:2 ratio was less acidic than with synthetic fertilizers. In contrast, Tang and Maggi (158) reported no significant soil quality changes after 20 years of urine application.
Ammonia volatilization from urine-treated soil affects air quality, contributing to pollutants like acidification and particulate matter (156). Emissions from urine application range from 0.2% to 0.4% of applied N, indicating relatively low volatilization (159). Nitrified, acidified urine with low pH has reduced NH3 emissions compared to alkalinized urine, which experiences higher volatilization due to urea hydrolysis, raising pH (26). Incorporating urine into soil through tillage or injection, and mixing biochar, can further reduce NH3 loss by limiting air exposure and adsorbing NH3 (79). These practices improve fertilizer efficiency and reduce environmental pollution.
Nitrous oxide (N2O), a potent GHG, receives less attention in the context of urine fertilization, despite emissions from post-urine treatments. Stored urine emits less N2O than mineral fertilizers and other organic components in incubation trials (160). Acidified urine showed slightly lower N2O emissions compared to untreated urine. Urine fertilization, which promotes nitrification, can potentially emit more NO and N2O than ammonium nitrate fertilizer, highlighting the need for further research on N2O emissions and mitigation strategies (79). Long-term use of urine fertilizers reduces synthetic fertilizer reliance, lowering GHG emissions and pollution while promoting sustainable agriculture and resilient food systems (156).
Soil biological reactions
Using source-separated urine in agriculture provides valuable nutrients but poses microbial risks (161). The World Health Organization (WHO) (162) recommends storing urine for six months to reduce microbial contamination, with a significant decline in microbial populations after 12 months, leaving only 46 operational taxonomic units (OTUs). However, long-term urine storage may lead to odor issues and nutrient loss, particularly through the volatilization of NH3, reducing the potential for nutrient recovery (163). Rotavirus and Shigella pose the highest risks during urine handling and fertilization (164). Soil microbiomes treated with urine were dominated by Proteobacteria (46%), Acidobacteria (14%), and Actinobacteria (8%) (165). Among the species, Nitrospirota was notably more abundant in single-dose urine treatments compared to water controls, showing the lowest resistance values in triple-dose treatments (-16.9% and -9.7%). Most other phyla exhibited positive resistance values between 7% and 88%, with nine phyla exceeding 50%. Urine treatments increased microbial diversity, with OTUs rising by 37% in single-dose and 47% in triple-dose treatments, leading to lower resistance (165).
Similarly, Lahr et al. (163) reported that 82 days of urine storage reduced bacterial diversity to about 130 OTUs, as urea hydrolysis elevated urine pH, killing pathogens like E. coli. However, some bacteria, such as Ignatzschineria indica, may survive. Urine treatments decrease soil pH and increase conductivity and mineral N, but do not completely eliminate bacterial infection risks (165). Four taxa more abundant in urine-treated soils may harbor halotolerant species: Sneathiella, Limibaculum halophilum, Lysobacter aestuarii, and Mesorhizobium, suggesting that urine salt levels favor halotolerant bacteria while allowing others to persist (161). Long-term urine fertilization could increase soil salinity, potentially altering bacterial community structure, making further research on its long-term effects essential.
Fate of pharmaceuticals in plants and soils after urine-derived fertilization
A key concern in agricultural reuse of human urine is the potential transmission of pathogens and contaminants, including pharmaceuticals, hormones and trace metals. While urine contains valuable nutrients such as N and P, it also carries pollutants. Pharmaceutical contaminants are classified into eight categories: antibiotics, hormones, antiepileptics, analgesics and anti-inflammatories, blood lipid regulators, β-receptor blockers and stimulants (166). Antibiotics are the most studied due to their widespread use in human medicine, veterinary practice and agriculture, and are consistently reported as the most prevalent pharmaceutical residues in the environment (167), raising concerns over persistence and antimicrobial resistance in urine-based fertilizers.
Pharmaceuticals in human urine include sulfamethoxazole, sulfamerazine, tetramethylpyrazine, ampicillin, and azithromycin (168). A study detected sulfamethoxazole, tetramethylpyrazine, and diclofenac in source-separated urine at 6800, 1280, and 72 mg L-1, respectively (164). Al-Farsi et al. (169) reported sulfamethoxazole and amoxicillin uptake (2.1 to 14,000 ng g-1) by radish roots. Analytical screening of source-separated urine detected 16 of 55 compounds, including anti-inflammatories and analgesics (diclofenac, ibuprofen, ketoprofen, methylprednisolone, naproxen, paracetamol), β-blockers (bisoprolol, propranolol), antibiotics (sulfamethoxazole, tetracycline, trimethoprim), caffeine, citalopram and female hormones (estriol, estrone, progesterone) (170). Military urine studies found 14 of 126 pharmaceuticals, including bisoprolol, hydrocortisone, ibuprofen, caffeine, naproxen, paracetamol, tetracycline, doxycycline and hormones (estradiol, estriol, estrogen, testosterone) (145).
The distribution and fate of pharmaceuticals within the water-soil-plant continuum are highly dynamic. Mordechay et al. (171) reported that irrigation with reclaimed wastewater introduced 35.5 ± 18.3 g ha-1 of emerging contaminants into fields, leading to soil accumulation of 129.4 ± 88.5 g ha-1 and measurable crop uptake, highest in banana (19.0 ± 22.7 g ha-1) and avocado (6.3 ± 4.2 g ha-1), with lower values in tomato, citrus, leafy vegetables, carrot and potato. A lysimeter study using worst-case and 10x worst-case spiked urine-derived fertilizers in lettuce found only eight quantifiable compounds, with extremely low uptake fractions (0.00004-0.0002% of applied mass). Additionally, they found negligible lifetime dietary exposure, including caffeine at 2.5% of a single therapeutic dose over 70 years, comparable to reclaimed-water irrigation (172). Nevertheless, high concentrations pose phytotoxicity risks. Barnett et al. (173) detected ciprofloxacin (up to 47 µg mL-1) and sulfamethoxazole (6.47 µg mL-1) in urine, causing dose and time-dependent toxicity in wheat, including root length reductions up to 63% and biomass loss, attributed to direct phytotoxicity and rhizosphere microbial disruption.
Once introduced into soils, pharmaceuticals may sorb to soil particles, undergo abiotic or biotic transformation, leach through profiles, or be taken up by plants (174). Soil properties strongly influence these processes, where higher clay content and organic matter increase retention and reduce bioavailability, collectively limiting uptake across crops (175). For example, carbamazepine accumulation decreased with increasing soil organic matter, and minimal uptake was observed in soils containing 2.89% organic matter with moderate sand (27.2%) and clay (20.7%) fractions (176). Furthermore, soil solution pH modulates uptake, particularly for weak acids and bases, whose charge state and interactions with organic matter determine mobility. Weak acidic pharmaceuticals generally exhibit limited plant uptake due to strong sorption to organic matter (177).
Removal of pharmaceuticalsApplication of biochar for the removal of pharmaceuticals
To mitigate pharmaceutical risks, numerous treatment strategies have been developed. Physical treatment methods are widely applied and rely on mechanisms such as electrical attraction, van der Waals forces, and gravity to separate contaminants (178). Biochar has been explored as a lower-cost alternative to activated carbon for pharmaceutical adsorption (179). Biochar can remove pharmaceuticals from human urine, but managing pharmaceutical-loaded biochar is a challenge. It must be recycled, burned, or securely landfilled (180). Fourier Transform Infrared analysis shows that biochar-pharmaceutical interactions involve π-π electron donor-acceptor interactions and hydrogen bonding, facilitated by carbonyl, hydroxyl, and aromatic compounds (181). High-temperature biochars, with reduced volatile compounds, exhibit better adsorption capacities, effectively interacting with compounds like sulfamethoxazole, tetracycline, and naproxen via π-π interactions (182). Microalgae-derived biochar, containing Ca3(PO4)2, CaCO3, and CaNaPO4, adsorbs tetracycline through metal complexation (183). Biochar pyrolyzed at 800°C exhibits maximum ciprofloxacin adsorption at pH 7, with capacity decreasing at higher pH (184). Manure-based biochar, with higher ash and oxygen content, is less effective for pharmaceutical adsorption (181). Chemically activating biochar enhances surface area, pore structure, and functional group interactions, significantly improving adsorption capacity (180).
Moreover, surface modifications of biochar enhance adsorption by altering surface chemistry (182). For instance, H3PO4-modified manure biochar improved tetracycline adsorption due to greater pore volume and more -COOH and -OH groups (185), while methanol-modified rice husk biochar showed similar effects from increased oxygen-containing groups (186). Application of H2O2-modified biochar effectively removed sulfonamide in synthetic urine (181). Biochar can remove nutrients and pharmaceuticals from human urine, but nutrient recovery risks pharmaceutical desorption. Applying biochar at 40 g L-1 to urine removes over 90% of pharmaceuticals like acetylsalicylic acid, paracetamol, ibuprofen, and diclofenac, with 20% N and phosphate co-removal (179). However, few studies focus on simultaneous nutrient-pharmaceutical removal, necessitating further research on desorption mechanisms and the environmental impact of urine-treated biochar.
Miscellaneous technologies
Membrane technologies are widely used to remove contaminants from wastewater. The NF270 nanofiltration membrane removed over 92% of pharmaceuticals and estrogenic compounds from source-separated urine (85). Ahmed et al. (187) studied chemical oxidation methods, such as ozonation/H2O2, UV photolysis/H2O2, and the photo-Fenton process, achieving nearly 100% pharmaceutical removal. However, these methods can be costly and complex for simple urine treatment. Yin et al. (188) studied the degradation of five pharmaceuticals, viz., atenolol, metoprolol, propranolol, fluoxetine, and venlafaxine, at different pH levels. Propranolol and venlafaxine degraded more at higher pH, while atenolol, metoprolol, and fluoxetine showed peak degradation at pH 7, 2, and 12, respectively, highlighting pH’s role in pharmaceutical degradation.
Hassan et al. (189) showed that synthetic ZnO nanoparticles removed over 99% of ibuprofen, ephedrine and propranolol from urine wastewater, while also removing 59.9% of total phosphorus, producing a treated stream suitable for agricultural reuse. Similarly, Wei et al. (190) reported that a porous Ti/SnO2-Bi reactive electrochemical membrane achieved complete removal of norfloxacin and >93% of sulfamethoxazole and ibuprofen, demonstrating effective pharmaceutical mitigation during nutrient recovery. Paredes-Laverde et al. (191) achieved 83.54% norfloxacin removal using coffee husk waste, outperforming rice husk. Nonetheless, high adsorbent costs, spent-material disposal challenges, and the fact that physical methods often separate rather than degrade pollutants limit long-term applicability.
Limited efficiency of conventional treatments has spurred interest in advanced chemical technologies. Advanced oxidation processes, including Fenton, ozonation, and electrochemical oxidation, generate reactive radicals that degrade persistent pharmaceuticals (192). Sonochemical oxidation achieved >90% pharmaceutical removal and reduced bacterial activity in urine (193). While Sebuso et al. (194) reported 95% photocatalytic degradation of doxycycline using graphene/ZnO nanocomposites from corn husks (195). Electrochemical treatments also control disinfectant by-products (196), and inorganic ions in sonochemical systems enhance hydroxyl radical attack (197). These results emphasize that urine-derived fertilizers are nutritionally valuable but require targeted treatments to mitigate pharmaceutical persistence and ensure environmental safety.
Granular activated carbon (GAC) is an energy-efficient method for removing micropollutants, including pharmaceuticals. Köpping et al. (198) studied the removal of 11 pharmaceuticals from nitrified and distilled urine using two GAC columns, viz., one with coarse GAC and the other with fine GAC. Both had similar removal efficiencies due to comparable internal surface areas, though the amount of GAC needed varied due to differences in intraparticle diffusion. Most nutrients in nitrified urine were retained while pharmaceuticals were removed. GAC removed 88% of carbamazepine and 77% of erythromycin but did not adsorb compounds like primidone or caffeine, due to their differing chemical properties (199). The application of GAC at 3000 mg L-1 removed over 90% of the pharmaceuticals within 1 hour, reaching 99% after 6 hours (123). Li et al. (200) reported that a 20 cm GAC sand filter removed 98.2% of pharmaceuticals, highlighting GAC’s effectiveness in wastewater treatment.
GAC and GAC + Polonite® removed 97% of pharmaceuticals, 57% more effective than sand filtration (201). This high efficiency was due to GAC’s macro- and mesopores, allowing micropollutants to reach micropores where sorption occurs. Hydrodynamic cavitation (HC) is an energy-efficient technology for degrading micropollutants, generating hydroxyl radicals through collapsing bubbles (202). Bagal and Gogate (203) used HC with a slit venturi device to remove diclofenac sodium, achieving 95% degradation and a 76% reduction in TOC when combined with UV/TiO2/H2O2, due to increased hydroxyl radical production. Wang et al. (204) combined HC with TiO2 photocatalysis for tetracycline degradation, achieving over 90% removal within 90 minutes, demonstrating a synergistic effect that outperformed individual processes. The technologies for treating pharmaceutical contaminants in human urine are illustrated in Table 5.
Technologies for treating pharmaceutical contaminants in human urine.
Pharmaceuticals
Processing technology
Treatment effect
Urine type
References
Antibiotics (e.g., Ciprofloxacin)
Activated carbon adsorption
85-90% removal of antibiotics
Real Urine
Paredes-Laverde et al. (205)
Carbamazepine
Photocatalysis (TiO2)
70-80% removal rate
Real Urine
Martínez-Escudero et al. (206)
Caffeine
Membrane bioreactor
99% removal
Synthetic Urine
Jiang et al. (182)
Clofibric acid
Electrocoagulation
80-85% removal
Hydrolyzed Urine
Ammar et al. (183)
Diclofenac
Bio-electrochemical system
75-85% removal
Hydrolyzed Urine
Jiménez-Bambague et al. (207)
Ibuprofen
Electro-Fenton process
92% degradation
Synthetic Urine
Jiménez-Bambague et al. (208)
Metformin
Electrochemical oxidation
95% degradation
Real Urine
Niknam et al. (186)
Fluoxetine
Struvite precipitation
50-60% removal
Synthetic Urine
Monetti et al. (34)
Naproxen
Nanofiltration
85-90% removal
Real Urine
Almuntashiri et al. (123)
Triclosan
Biochar adsorption
70-75% removal
Real Urine
Czech et al. (180)
Diclofenac
Fenton oxidation
90-95% degradation
Hydrolyzed Urine
Wang et al. (32)
Norfloxacin
RH and CH adsorption
Removal rates were 30.6% and 83.54%, respectively
Synthetic urine
Paredes-Laverde et al. (191)
Sulfonamides
Biochar/H2O2
Removal rates all over 80%
Hydrolysis of urine
Sun et al. (181)
Estradiol
Catalytic wet peroxide oxidation
88-92% removal
Real Urine
Sirinukulwatana et al. (209)
Environmental and socio-economic aspects of urine-derived fertilizerLife cycle assessment insights on the environmental performance of urine-derived fertilizers
While the fertilizer efficiency of source-separated human urine is well established, its environmental performance requires system-level evaluation. Life cycle assessment (LCA) studies comparing wastewater treatment systems with and without urine separation have assessed impacts on climate change, eutrophication, acidification, resource depletion, and energy demand (210–212). These studies show that environmental outcomes are mainly driven by nutrient concentration, recovery efficiency, energy use, transport and system decentralization. Pradel and Aissani (211) demonstrated that sludge-derived phosphate fertilizers generally impose higher environmental burdens than conventional superphosphate across most impact categories. It includes climate change, eutrophication, acidification, ecotoxicity, human toxicity, ozone depletion, and photochemical oxidation, largely due to low phosphorus concentrations and high energy and chemical inputs.
Further LCA evidence indicates that wastewater-based nutrient recycling generally provides net environmental benefits, especially when source separation and reduced chemical inputs are applied (212). Urine separation offers the most balanced environmental and economic performance among sanitation options, whereas recovery from mixed excreta may suit areas without sewer infrastructure (210). In rural and decentralized systems, source-separated urine enables recovery of up to four times more phosphorus and over thirty times more nitrogen than conventional on-site systems, while reducing eutrophication impacts to one fifth (213). Accordingly, ecological sanitation and source-separating approaches show favorable system-level outcomes (214). Although added infrastructure increases environmental loads, lower operational and maintenance demands often result in reduced life cycle costs despite higher initial investments (215).
City and building-scale LCAs underline the importance of decentralization and energy sources. For instance, Hilton et al. (216) reported that urine diversion reduced greenhouse gas emissions (29-47%), energy demand (26-41%), freshwater use (50%), and eutrophication (25-64%) relative to conventional wastewater treatment and synthetic fertilizers. Similarly, Martin et al. (217) found that urine-based fertilizer value chains lowered climate change and eutrophication impacts in wheat production through avoided wastewater treatment, with trade-offs linked to treatment technology and cumulative energy demand. At the building scale, environmental performance is highly sensitive to energy intensity, scale, and electricity mix, emphasizing the need for low-carbon energy and reduced transport distances (218). Overall, LCA evidence indicates that urine diversion and agricultural reuse substantially reduce nutrient losses and eutrophication risks.
Cost effectiveness of urine-derived fertilizer over conventional nitrogen fertilizers
Human urine is a promising, cost-effective alternative to traditional compost and chemical fertilizers in agriculture (219). The first step in utilizing urine as fertilizer is source separation, requiring urine-diverting toilets or urinals. Installation costs vary, with a single urine-diverting toilet ranging from 150 to 500 USD (220). In larger settings like schools or public buildings, costs rise due to multiple units and plumbing modifications, while community collection systems may range from 5,000 to 20,000 USD. Regular maintenance, including cleaning and repairs, is crucial, with annual costs between 50 and 200 USD per unit (221). Once collected, urine must be treated and stabilized for safe use as fertilizer. Alkaline stabilization, which raises pH with lime to kill pathogens, costs between 0.10 to 0.20 USD per gallon (219). Anaerobic digestion is another method that stabilizes urine, with setup costs of 1,000 to 3,000 USD and operational costs of 0.05 to 0.10 USD per gallon (81).
The economic value of urine-based nutrient recovery varies by region and technology. N recovery has been estimated at 29–550 million USD annually in low- and middle-income economies, though feasibility is context specific (222). Recovered nutrients can be cost-competitive with synthetic fertilizers when processing and transport costs are low and sanitation integration reduces wastewater treatment expenses (216). However, fertilizer subsidies often necessitate policy or financial support (223). In Nairobi, N recovery from source-separated urine via ion exchange was 40% cheaper than untreated wastewater disposal and produced ammonium sulphate at lower cost than conventional fertilizers (224). Similar outcomes were reported in Uganda when recovered nutrients matched or undercut synthetic fertilizer prices (222). However, high upfront capital requirements mean long-term returns and supportive policy frameworks remain essential for viability (216).
Decentralized nutrient-recovery systems reduce dependence on imported fertilizers, create local employment and enhance food security (225). However, their sustainability depends on scalability, logistics and market demand, often requiring incentives to compete with synthetic fertilizer industries (226). Urine-derived fertilizers offer major energy advantages by avoiding industrial nitrogen fixation and mineral extraction. The Haber-Bosch process alone accounts for 1-2% of global energy use (227), while phosphate fertilizer production adds further energy and environmental burdens from mining and processing (228). By capturing nutrients directly, urine diversion bypasses these steps and can reduce GHG emissions by 29-47% (229). Proper storage is crucial to prevent N loss, requiring airtight containers priced at 50 to 200 USD (230). Applying urine-based fertilizer necessitates specialized equipment, such as drip irrigation systems or sprayers, which range from 500 to 5,000 USD, along with labor costs of 10 to 20 USD per hour (19).
Transport logistics are a key constraint for urine-derived fertilizers due to high water content, which can increase transport energy up to 3.5 times compared with synthetic fertilizers (216). Feasibility depends on distance, nutrient concentration, infrastructure and costs, with a persistent urban-rural spatial mismatch (231). In regions such as North America, South America and Oceania, transporting bulk, water-rich products are cost-prohibitive without concentration technologies (232). Spatial analyses, including a U.S. phosphorus-recovery mapping study, emphasize opportunities to supply nearby agricultural demand efficiently (233). Nevertheless, transport inefficiencies remain a barrier, requiring coordinated technological, spatial and policy strategies, such as regional processing hubs and integration into urban sanitation planning (234).
To evaluate the cost-effectiveness of urine as fertilizer, it’s important to compare it with traditional compost and commercial fertilizers. Organic fertilizers, such as compost or manure, typically cost between 20 to 50 USD per ton but have lower nutrient concentrations depending on their source and quality (220). In contrast, synthetic N fertilizers like urea and ammonium nitrate range from 500 to 1,000 USD per ton, offering high N content (46% for urea, 34% for ammonium nitrate) (81). The preliminary techno-economic evaluation shows that, despite initial costs for urine separation, treatment, and storage, urine-based fertilizers are cost-effective compared to synthetic and organic options (Table 6). Long-term savings from reduced synthetic fertilizer purchases can offset setup expenses, while offering significant environmental benefits and promoting ecosystem balance.
Preliminary cost summary: Comparing costs of using human urine, traditional compost, and inorganic fertilizers.
Cost factor
Urine fertilizer
Traditional compost
Synthetic fertilizer
References
Separation & Collection
200–700 USD per unit
–
–
VanderZaag et al. (230)
Treatment & Stabilization
0.15-0.30 USD per gallon
20–50 USD per ton
–
Kabdaşlı and Tünay (221)
Storage Costs
50–200 USD per container
50–150 USD per storage unit
–
Dos Santos et al. (219)
Volatilization Management
0.05-0.10 USD per gallon
–
–
Simha et al. (57)
Application Equipment
500–5000 USD per system
50–150 USD per acre
50–150 USD per acre
Ray et al. (19)
Labor Costs
10–20 USD per hour
10–20 USD per hour
10–20 USD per hour
IFDC- International Fertilizer Development Center (235)
Environmental Savings
500–1000 USD per ton (substitution)
–
–
Manufacturing costs
–
–
150–350 USD per ton
Social perceptions and attitudinal issues
Acceptance of human urine as a fertilizer and of urine-fertilized food varies widely across countries due to cultural norms, social values and risk perceptions. Direct agricultural use faces opposition due to waste categorization, odor, health concerns, and societal attitudes (36). Despite its nutritional value, urban populations often discourage urine ingestion. In many Western societies, stigma surrounds the use of human waste in agriculture, driven by hygiene, safety, and aesthetic concerns (160). Conversely, in some Asian cultures, the historical use of “night soil” fosters familiarity, facilitating acceptance (236). Cultural factors also play a role, with 38% and 26% of consumers in Ghana and Nigeria, respectively, objecting to urine fertilizers (159). In contrast, only 6% of South Africans oppose raw and nitrified urine, and 79% are willing to consume plants fertilized with it (26).
Survey-based studies indicate that consumers generally accept urine-fertilized products when food safety and environmental risks are addressed and prices do not increase (170). While farmers support urine reuse when costs and agronomic performance match conventional fertilizers (237). Although a potential market exists, adoption remains constrained by limited legislation and weak coordination across sanitation, agriculture and food systems (60). Concerns over urine-derived fertilizers largely stem from scepticism toward sewage sludge, despite major improvements in wastewater quality over the past 30–40 years and no documented long-term health or environmental risks. Empirical studies show no significant differences in heavy metals, micropollutants, soil properties, or microbiological quality compared with conventional fertilizers (238, 239). Nonetheless, historical stigma persists and source-separated urine is often perceived as equally risky due to its association with sludge (170). Odor concerns, fears of pathogens and pharmaceuticals, and cultural taboos further limit acceptance. Therefore, adoption depends on farmer confidence in safety, nutrient reliability and agronomic performance, supported by transparent communication, extension services and participatory demonstrations.
Economic factors play a crucial role in the feasibility and acceptance of urine-derived fertilizers. In areas with limited access to synthetic fertilizers, these alternatives are appealing due to their low cost and local availability (236). In wealthier regions, while the abundance of synthetic fertilizers may diminish perceived need, growing awareness of environmental sustainability and economic benefits can foster interest in urine-derived options (159). Public approval is vital for the success of urine source separation techniques. Chipako and Randall (21) conducted an online study revealing that 87% of respondents would use urinals that produce fertilizer. However, support was lower among female participants regarding urine-soiled toilet paper disposal. Notably, 79% of respondents expressed willingness to consume food grown with urine-derived fertilizer.Educating consumers about sanitation alternatives and source separation is vital for promoting urine acceptance as fertilizer. Legislative support and effective communication among sanitation stakeholders are vital for achieving the acceptability of urine as a fertilizer (236). Long-term studies by Rutgersson et al. (239) have found that using sewage sludge as a fertilizer poses no health or environmental hazards. However, lingering doubts persist due to historical perceptions of sludge and urine as harmful, impeding their broader adoption. Addressing cultural attitudes, religious beliefs, and economic constraints through tailored strategies can improve acceptance and implementation, promoting sustainable nutrient recycling and environmental conservation. While these systems offer an alternative to industrial fertilizers, they come with infrastructure expenses and a greater environmental load. The estimated yearly nutrient recovery capacity from human urine in densely populated areas worldwide is shown in Figure 4.
Global human urine nutrient recovery potential in the context of population demographics and NPK fertilizer demand during 2023. This figure illustrates the 2023 global population distribution by age group, NPK fertilizer consumption, and imports across most populated countries, alongside the annual nutrient recovery potential from human urine. Population data are divided into children (0–14), adults (15–64), and elderly (>65). Annual urine volumes per person are estimated at 200–250 L for children, 500–550 L for adults, and 400–450 L for the elderly, based on mean values reported by Rosinger (240) and Ajiboye et al. (17). These correspond to nutrient excretion rates of approximately 1.6, 4.0, and 3.2 kg N; 0.16, 0.40, and 0.32 kg P; and 0.36, 0.90, and 0.72 kg K, respectively. The comparison highlights the disparity between synthetic fertilizer demand and the untapped potential of human urine as a sustainable nutrient source, emphasizing its role in reducing fertilizer dependency and promoting circular nutrient management. Source: Ritchie et al. (241); Nutrien Ltd (242); International Fertilizer Association (4).
World map highlighting the ten most populous countries in 2023, with population breakdowns by age group for each country. Three bar charts compare these countries’ 2023 global NPK fertilizer consumption, fertilizer imports, and estimated nutrient recovery potential from human urine, using consistent color coding for each country. Each chart includes both visual bars and accompanying numerical tables for nitrogen, phosphate, and potash.Safety measures while handling human urine
Human urine offers a cost-effective alternative to chemical fertilizers and traditional compost, benefiting economically disadvantaged farmers by reducing costs and minimizing pollution from waste disposal and fertilizer use (159). However, concerns include potential viral transmission, pollutants like heavy metals and pharmaceuticals, challenges in collection, handling, and storage, especially in urban areas. Poor storage can cause odor issues and pose health risks to workers handling urine (236). Farmers in both developed and poor countries can utilize urine in agriculture, provided that proper safeguards are taken. Some of the safety measures (145) to be taken are,
Avoid high urine application rates, which can increase soil salinity.
It is advisable to avoid direct spraying on harvested plant parts and to refrain from fertilizing crops within a month before harvest.
Avoid improper timing or unequal distribution of urine in fields, which results in significant crop losses.
For sanitary reasons, urine should be stored in a sealed receptacle for six months before use.
Hands should be thoroughly cleaned after handling urine, as with other manure.
Future prospects
Despite growing global interest in recycling human urine as a sustainable fertilizer, several key research gaps must be addressed to facilitate its large-scale adoption in agriculture. One critical priority is the development of decentralized urine collection and treatment systems involving specialized toilet systems such as urine diversion toilets and fertilizer-producing urinals. It enables efficient urine collection, that are economically viable, culturally acceptable, and technically efficient, particularly in rural and peri-urban areas. These systems should incorporate simple yet effective stabilization methods such as acidification, biochar addition, or alkaline treatment to prevent N loss and reduce odor during storage and transport. One major challenge involves separating urine from healthy and unhealthy individuals to avoid the transmission of contaminants. While technically feasible through continuous health monitoring and defined protocols, such an approach faces practical and financial constraints and is currently more viable in regulated environments such as hospitals or community health programs.
To ensure safety in agricultural use, urine-derived products must undergo rigorous toxicity testing to detect pharmaceuticals, pathogens, and other potentially harmful residues. While technologies like activated carbon, advanced oxidation, and membrane-based separations show promise, their integration into scalable, low-cost treatment systems remains a challenge. Existing agronomic studies have largely focused on short-term benefits, yet there is a pressing need for long-term field experiments to assess the cumulative effects of urine application on soil pH, salinity, microbial ecology, and nutrient dynamics. Such studies will help establish site-specific guidelines for sustainable and safe use. Additionally, the formulation of slow-release or enhanced-efficiency urine-based fertilizers, possibly using biochar, zeolites, or biodegradable carriers, represents a promising avenue to improve nutrient use efficiency and minimize environmental losses. Future research must also include comprehensive life-cycle assessments comparing urine-derived and synthetic fertilizers in terms of energy inputs, GHG emissions, and cost-effectiveness. This will help determine the true sustainability potential of urine recycling technologies. Interdisciplinary research involving behavioral science, education, and stakeholder engagement is essential to overcome public acceptance. By addressing these research priorities, human urine can be transformed from a waste stream into a valuable input for climate-resilient, resource-efficient, and sustainable agriculture.
Conclusions
The global dependence on synthetic fertilizers has contributed to environmental degradation, high energy consumption, and reduced nutrient use efficiency. In response, this review presents human urine as a viable and sustainable alternative, offering a renewable, nutrient-rich resource that can be effectively recovered and reused in agriculture. Through a detailed bibliometric analysis covering publications from 2011 to 2025, this study reveals increasing global interest in urine-based fertilizers, especially in the areas of nutrient recycling, decentralized sanitation, and ecological farming practices. Various nutrient recovery technologies have been developed, each differing in efficiency, scalability, and cost. Notably, integrated methods such as biochar stabilization, acidification or combined drying and struvite precipitation have shown potential in reducing odor, improving nutrient retention and enhancing fertilizer value. When properly collected and treated, urine-derived nutrients can match synthetic fertilizers in promoting crop growth, root development, biomass accumulation and resilience under saline or nutrient-poor conditions.
Moreover, urine-based fertilization offers environmental benefits by reducing reliance on chemical inputs and lowering GHG emissions associated with urea production. However, challenges such as public acceptance, regulatory barriers and the risk of soil contamination remain. Future research should focus on large-scale, multi-season field trials across varied soil types and cropping systems to validate agronomic performance and long-term soil impacts. Developing internationally accepted standards for urine collection, stabilization, storage and application rates is also essential to ensure quality and safety. Additionally, supportive policy mechanisms such as subsidies, certification systems, incentives for decentralized sanitation technologies and integration into circular bioeconomy frameworks will be critical to accelerate adoption. With coordinated advancements in research, regulation and stakeholder engagement, urine recycling has the potential to strengthen circular nutrient management, improve soil health and support climate-resilient and sustainable agriculture.
Data availability statement
The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding authors.
The authors acknowledge the Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India, for providing library and web source facilities for the review paper. The authors also acknowledge VOS viewer software (version 1.6.20) and Bibliometrix software and R (version 4.50) which were used to create network maps of co-citation, co-occurrence, and keyword co-occurrence.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declared that generative AI was not used in the creation of this manuscript.
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ReferencesBasuPMandalMJanaSBiswasARayS.
Impact of anthropogenic activities on global warming and energy demand. Intersection Global Energy Politics Climate Change: A Compr Anal Energy Markets Econ. (2025) pp:63–81. doi: 10.1007/978-981-96-0535-4_3, PMID: 41808729MartrePDueriSGuarinJREwertFWebberHCalderiniD.
Global needs for nitrogen fertilizer to improve wheat yield under climate change. Nat Plants. (2024) 10:1081–90. doi: 10.1038/s41477-024-01739-3, PMID: 38965400ShuklaAKBeheraSKChaudhariSKSinghG.
Fertilizer use in Indian agriculture and its impact on human health and environment. Indian J Fertil. (2022) 18:218–37.
International Fertilizer Association (IFA).
Fertilizer trade statistics and market overview 2023 (2024). Available online at: https://www.fertilizer.org (Accessed June 12, 2025).
Food and Agriculture Organization of the United Nations (FAO). World fertilizer trends and outlook to 2026. Rome:
FAO (2022).
RobertsonGPGroffmanPM.
Nitrogen transformations. In: Soil microbiology, ecology and biochemistry (2024)
Elsevier. p. 407–38. doi: 10.1016/B978-0-12-822941-5.00014-4, PMID: 41813336ButlerCFanYGrewalSWinterLR.
At-field and on-demand nitrogenous fertilizer synthesis. ACS Sustain Chem Eng. (2023) 11:5803–18. doi: 10.1021/acssuschemeng.2c06551, PMID: 41799136ZhangWLiangZHeXWangXShiXZouC.
The effects of controlled release urea on maize productivity and reactive nitrogen losses: A meta-analysis. Environ pollut. (2019) 246:559–65. doi: 10.1016/j.envpol.2018.12.059, PMID: 30594896RenKSunYZouHLiDLuCDuanY.
Effect of replacing synthetic nitrogen fertilizer with animal manure on grain yield and nitrogen use efficiency in China: a meta-analysis. Front Plant Sci. (2023) 14:1153235. doi: 10.3389/fpls.2023.1153235, PMID: 37251776RandiveKRautTJawadandS.
An overview of the global fertilizer trends and India’s position in 2020. Miner Econ. (2021) pp:1–14. doi: 10.1007/s13563-020-00246-z, PMID: 41810330MustaffaMRAFPandianKChitraputhirapillaiSKuppusamySDhanushkodiK.
Synthesis of biochar-embedded slow-release nitrogen fertilizers: Mesocosm and field scale evaluation for nitrogen use efficiency, growth and rice yield. Soil Use Manage. (2024) 00:1–17. doi: 10.1111/sum.12959, PMID: 41808597BandalaER.
Sustainable developing goals: SDG 6 and its significance for sustainable growth. In: Circular economy applications for water security.
CRC Press (2024). p. 5–20.
QadirMDrechselPJiménez CisnerosBKimYPramanikAMehtaP.
Global and regional potential of wastewater as a water, nutrient and energy source. Nat Resour Forum. (2020) 44:40–51. doi: 10.1111/1477-8947.12187, PMID: 41808597DingYLiDLiX.
Determinants of child mortality in the world: Focusing on the impacts of basic, clean and safe sanitation services using a fixed effects regression. In: 2021 smart city challenges & Outcomes for urban transformation (SCOUT) (2021) India:
IEEE. p. 24–30. doi: 10.1109/SCOUT54618.2021.00017, PMID: 41116384SimwambiAKapembwaMAKapandaK.
Effects of poor solid waste management on faecal sludge emptying, treatment and disposal services in Lusaka. Eur J Appl Sci. (2023) 11(4):330–60. doi: 10.14738/aivp.114.15405WerknehAAGebruSB.
Development of ecological sanitation approaches for integrated recovery of biogas, nutrients and clean water from domestic wastewater. Resour Environ Sustain. (2023) 11:100095. doi: 10.1016/j.resenv.2022.100095, PMID: 41813336AjiboyeTOOgunbiyiODOmotolaEOAdeyemiWJAgboolaOOOnwudiweDC.
Urine: useless or useful “waste”? Results Eng. (2022) 17:100522. doi: 10.1016/j.rineng.2022.100522, PMID: 41813336SeneMHijikataNUshijimaKFunamizuN.
Application of human urine in agriculture. Resource-Oriented Agro-sanitation Systems: Concept Business Model Technology. (2018) pp:213–42. doi: 10.1007/978-4-431-56835-3_15, PMID: 41808728RayHPerreaultFBoyerTH.
Rejection of nitrogen species in real fresh and hydrolyzed human urine by reverse osmosis and nanofiltration. J Environ Chem Eng. (2020) 8:103993. doi: 10.1016/j.jece.2020.103993, PMID: 41813336ZhangLLiuJYangLYuZChenJChuH.
Interfacial solar evaporation toward efficient recovery of clean water and concentration of nutrients from urine with polypyrrole-based photothermal conversion films. Resour Conserv Recycl. (2023) 188:106645. doi: 10.1016/j.resconrec.2022.106645, PMID: 41813336ChipakoTLRandallDG.
Urinals for water savings and nutrient recovery: A feasibility study. Water SA. (2019) 45:266–77. doi: 10.4314/wsa.v45i2.14SharmaMPangJMickanBSRyanMHJenkinsSNSiddiqueKH.
Wastewater-derived struvite has the potential to substitute for soluble phosphorus fertiliser for growth of chickpea and wheat. J Soil Sci Plant Nutr. (2024) pp:1–15. doi: 10.1007/s42729-024-01727-8, PMID: 41810330HarderRWielemakerRLarsenTAZeemanGÖbergG.
Recycling nutrients contained in human excreta to agriculture: Pathways, processes, and products. Crit Rev Environ Sci Technol. (2019) 49:695–743. doi: 10.1080/10643389.2018.1558889, PMID: 41799851LarsenTARiechmannMEUdertKM.
State of the art of urine treatment technologies: A critical review. Water Res X. (2021) 13:100114. doi: 10.1016/j.wroa.2021.100114, PMID: 34693239SimhaPCourtneyCRandallDG.
An urgent call for using real human urine in decentralized sanitation research and advancing protocols for preparing synthetic urine. Front Environ Sci. (2024) 12:1367982. doi: 10.3389/fenvs.2024.1367982, PMID: 41810299ChipakoTLRandallDG.
Urine treatment technologies and the importance of pH. J Environ Chem Eng. (2020) 8:103622. doi: 10.1016/j.jece.2019.103622, PMID: 41813336DonthuNKumarSMukherjeeDPandeyNLimWM.
How to conduct a bibliometric analysis: An overview and guidelines. J Business Res. (2021) 133:285–96. doi: 10.1016/j.jbusres.2021.04.070, PMID: 41813336BeijerSDasSHelmusRScheerPJansenBSlootwegC.
Urine as biobased fertilizer: The Netherlands as case study. Sustainability Circularity NOW. (2024) 1–13. doi: 10.1055/a-2334-6930, PMID: 41812672RandallDGBrisonAUdertKM.
High temperatures and CO2 dissolution can cause nitrogen losses from urine stabilized with base. Front Environ Sci. (2022) 10:998743. doi: 10.3389/fenvs.2022.998743, PMID: 41810299LedezmaPJermakkaJKellerJFreguiaS.
Recovering nitrogen as a solid without chemical dosing: Bio-electroconcentration for recovery of nutrients from urine. Environ Sci Technol Lett. (2017) 4:119–24. doi: 10.1021/acs.estlett.7b00024, PMID: 41799136WeiSPvan RossumFvan de PolGJWinklerMKH.
Recovery of phosphorus and nitrogen from human urine by struvite precipitation, air stripping and acid scrubbing: A pilot study. Chemosphere. (2018) 212:1030–7. doi: 10.1016/j.chemosphere.2018.08.154, PMID: 30286532WangXWangYZhangJDuanmuPZhengLHassonSU.
Degradation of diclofenac in urine by electro-permanganate process driven by microbial fuel cells. Water. (2021) 13:2047. doi: 10.3390/w13152047, PMID: 41725453WorcesterEMBergslandKJGillenDLCoeFL.
Mechanism for higher urine pH in normal women compared with men. Am J Physiol Renal Physiol. (2018) 314:F623–9. doi: 10.1152/ajprenal.00494.2017, PMID: 29357436MonettiJNieradzikLFreguiaSChoiPMO’BrienJWThomasKV.
Urea hydrolysis and long-term storage of source-separated urine for reuse as fertiliser is insufficient for the removal of anthropogenic micropollutants. Water Res. (2022) 222:118891. doi: 10.1016/j.watres.2022.118891, PMID: 35907300HohlKSMeirellesEFCarliniCR.
Versatility of ureases: many uses for biotechnological and medical applications. In: Ureases. (2024) pp:421–43. doi: 10.1016/B978-0-323-91800-8.00012-6, PMID: 41813336AndreevNRonteltapMBoinceanBWernliMZubcovEBagrinN.
Lactic acid fermentation of human urine to improve its fertilizing value and reduce odour emissions. J Environ Manage. (2017) 198:63–9. doi: 10.1016/j.jenvman.2017.04.059, PMID: 28448847MobleyHLHausingerRP.
Microbial ureases: significance, regulation, and molecular characterization. Microbiol Rev. (1989) 53:85–108. doi: 10.1128/mr.53.1.85-108.1989, PMID: 2651866MarandiAPolikarpusMJõelehtA.
A new approach for describing the relationship between electrical conductivity and major anion concentration in natural waters. Appl Geochem. (2013) 38:103–9. doi: 10.1016/j.apgeochem.2013.09.003, PMID: 41813336MnkeniPNKutuFRMuchaonyerwaPAustinLM.
Evaluation of human urine as a source of nutrients for selected vegetables and maize under tunnel house conditions in the Eastern Cape, South Africa. Waste Manag Res. (2008) 26:132–9. doi: 10.1177/0734242X07079179, PMID: 18578152WalterXASantoroCGreenmanJIeropoulosIA.
Scalability and stacking of self-stratifying microbial fuel cells treating urine. Bioelectrochemistry. (2020) 133:107491. doi: 10.1016/j.bioelechem.2020.107491, PMID: 32163891SantoroCGarciaMJSWalterXAYouJTheodosiouPGajdaI.
Urine in bioelectrochemical systems: an overall review. ChemElectroChem. (2020) 7:1312–31. doi: 10.1002/celc.201901995, PMID: 32322457LinXJinZJiangSWangZWuSBeiK.
Fertilizer recovery from source-separated urine by evaporation with a combined process of dehumidification and the addition of absorbent resin supplement. Water Res. (2024) 248:120865. doi: 10.1016/j.watres.2023.120865, PMID: 38000227AlemayehuYADemozAADegefuMAGebreeyessusGDDemessieSF.
Effect of human urine application on cabbage production and soil characteristics. J Water Sanit. Hyg Dev. (2020) 10:262–75. doi: 10.2166/washdev.2020.136, PMID: 41533551SicilianoALimontiCCurcioGMMolinariR.
Advances in struvite precipitation technologies for nutrients removal and recovery from aqueous waste and wastewater. Sustainability. (2020) 12:7538. doi: 10.3390/su12187538, PMID: 41725453RayHPerreaultFBoyerTH.
Urea recovery from fresh human urine by forward osmosis and membrane distillation (FO–MD). Environ Sci: Water Res Technol. (2019) 5:1993–2003. doi: 10.1039/C9EW00720B, PMID: 41811194BonczMAFormaginiELArimaFXPauloPL.
Methods for stabilising and concentrating human urine for use as a fertilizer. Athens Greece. (2016).
MoharramzadehSOngSKAllemanJCetinKS.
Stabilization and concentration of nitrogen in synthetic urine with peracetic acid and progressive freeze concentration. J Environ Chem Eng. (2022) 10:107768. doi: 10.1016/j.jece.2022.107768, PMID: 41813336JiangFChenYMackeyHRChenGHVan LoosdrechtMCM.
Urine nitrification and sewer discharge to realize in-sewer denitrification to simplify sewage treatment in Hong Kong. Water Sci Technol. (2011) 64:618–26. doi: 10.2166/wst.2011.491, PMID: 22097039Rezaei BehbehaniGSabouryAATaherkhaniABarzegarLMollaagazadeA.
A thermodynamic study on the binding of mercury and silver ions to urease. J Therm Anal Calorim. (2011) 105:1081–6. doi: 10.1007/s10973-011-1729-9, PMID: 41810330HellströmDJohanssonEGrennbergK.
Storage of human urine: acidification as a method to inhibit decomposition of urea. Ecol Eng. (1999) 12:253–69. doi: 10.1016/S0925-8574(98)00074-3, PMID: 41276264RandallDGKrähenbühlMKöppingILarsenTAUdertKM.
A novel approach for stabilizing fresh urine by calcium hydroxide addition. Water Res. (2016) 95:361–9. doi: 10.1016/j.watres.2016.03.007, PMID: 27055084MuirheadDCarrierC.
Comparison of four strong acids on the precipitation potential of gypsum in brines during distillation of pretreated, augmented urine: preliminary results. Proc 42nd Int Conf Environ Syst. (2012) p:3528. doi: 10.2514/6.2012-3528, PMID: 34531064SaettaDBoyerTH.
Mimicking and inhibiting urea hydrolysis in nonwater urinals. Environ Sci Technol. (2017) 51:13850–8. doi: 10.1021/acs.est.7b03571, PMID: 29095605RayHSaettaDBoyerTH.
Characterization of urea hydrolysis in fresh human urine and inhibition by chemical addition. Environ Sci: Water Res Technol. (2018) 4:87–98. doi: 10.1039/C7EW00271H, PMID: 41811194HashemiSHanM.
Methods for controlling stored urine odor in resource-oriented sanitation. J Water Sanit Hyg Dev. (2017) 7:507–14. doi: 10.2166/washdev.2017.098, PMID: 41533551MichaelPS.
The importance of sustainable management of acid soils in the humid tropics under climate change and the future research directions. Ecofeminism Clim Change. (2023) 4:39–50.
SimhaPLalanderCNordinAVinneråsB.
Alkaline dehydration of source-separated fresh human urine: Preliminary insights into using different dehydration temperature and media. Sci Total Environ. (2020) 733:139313. doi: 10.1016/j.scitotenv.2020.139313, PMID: 32446074GeinzerM. Inactivation of the urease enzyme by heat and alkaline pH treatment: retaining urea nitrogen in urine for fertilizer use.
Swedish Univ Agric Sci (SLU, Uppsala, Sweden (2017).
SenecalJVinneråsB.
Urea stabilisation and concentration for urine-diverting dry toilets: urine dehydration in ash. Sci Total Environ. (2017) 586:650–7. doi: 10.1016/j.scitotenv.2017.02.038, PMID: 28215808SimhaPLalanderCRamanathanAVijayalakshmiCMcConvilleJRVinneråsB.
What do consumers think about recycling human urine as fertiliser? Perceptions and attitudes of a university community in South India. Water Res. (2018) 143:527–38. doi: 10.1016/j.watres.2018.07.006, PMID: 30007256LvYLiZZhouXChengSZhengL.
Stabilization of source-separated urine by heat-activated peroxydisulfate. Sci Total Environ. (2020) 749:142213. doi: 10.1016/j.scitotenv.2020.142213, PMID: 33370919XiaoRBaiLLiuKShiYMinakataDHuangCH.
Elucidating sulfate radical-mediated disinfection profiles and mechanisms of Escherichia coli and Enterococcus faecalis in municipal wastewater. Water Res. (2020) 173:115552. doi: 10.1016/j.watres.2020.115552, PMID: 32062220FumasoliAEtterBSterkeleBMorgenrothEUdertKM.
Operating a pilot-scale nitrification/distillation plant for complete nutrient recovery from urine. Water Sci Technol. (2016) 73:215–22. doi: 10.2166/wst.2015.485, PMID: 26744953IkematsuMKanedaKIsekiMYasudaM.
Electrochemical treatment of human urine for its storage and reuse as flush water. Sci Total Environ. (2007) 382:159–64. doi: 10.1016/j.scitotenv.2007.03.028, PMID: 17462709De PaepeJDe PryckLVerliefdeARRabaeyKClauwaertP.
Electrochemically induced precipitation enables fresh urine stabilization and facilitates source separation. Environ Sci Technol. (2020) 54:3618–27. doi: 10.1021/acs.est.9b06804, PMID: 32049503ClauwaertPDe PaepeJJiangFAlonso-FariñasBVaiopoulouEVerliefdeA.
Electrochemical tap water softening: A zero chemical input approach. Water Res. (2020) 169:115263. doi: 10.1016/j.watres.2019.115263, PMID: 31734395OlechZZaborskaWKotM.
Jack bean urease inhibition by crude juices of Allium and Brassica plants: determination of thiosulfinates. Food Chem. (2014) 145:154–60. doi: 10.1016/j.foodchem.2013.08.044, PMID: 24128461ZhengpingWVan CleemputODemeyerPBaertL.
Effect of urease inhibitors on urea hydrolysis and ammonia volatilization. Biol Fertil Soils. (1991) 11:43–7. doi: 10.1007/BF003358334, PMID: 41810330LiuYDaiQJinXDongXPengJWuM.
Negative impacts of biochars on urease activity: high pH, heavy metals, polycyclic aromatic hydrocarbons, or free radicals? Environ Sci Technol. (2018) 52:12740–7. doi: 10.1021/acs.est.8b00672, PMID: 30350570RoseCParkerAJeffersonBCartmellE.
The characterization of feces and urine: a review of the literature to inform advanced treatment technology. Crit Rev Environ Sci Technol. (2015) 45:1827–79. doi: 10.1080/10643389.2014.1000761, PMID: 26246784PathyARayJParamasivanB.
Challenges and opportunities of nutrient recovery from human urine using biochar for fertilizer applications. J Clean. Prod. (2021) 304:127019. doi: 10.1016/j.jclepro.2021.127019, PMID: 41813336PatelAMungrayAAMungrayAK.
Technologies for the recovery of nutrients, water and energy from human urine: A review. Chemosphere. (2020) 259:127372. doi: 10.1016/j.chemosphere.2020.127372, PMID: 32599379CourtneyCRandallDG.
Concentrating stabilized urine with reverse osmosis: how does stabilization method and pre-treatment affect nutrient recovery, flux, and scaling? Water Res. (2022) 209:117970. doi: 10.1016/j.watres.2021.117970, PMID: 34936975OsipiSRSecchiARBorgesCP.
Cost analysis of forward osmosis and reverse osmosis in a case study. In: Current trends and future developments on (Bio-) membranes (2020)
Elsevier. p. 305–24. doi: 10.1016/B978-0-12-816777-9.00013-7, PMID: 41813336EkMBergströmRBjurhemJEBjörleniusBHellströmD.
Concentration of nutrients from urine and reject water from anaerobically digested sludge. Water Sci Technol. (2006) 54:437–44. doi: 10.2166/wst.2006.924, PMID: 17302349VolpinFYuHChoJLeeCPhuntshoSGhaffourN.
Human urine as a forward osmosis draw solution for the application of microalgae dewatering. J Hazard Mater. (2019) 378:120724. doi: 10.1016/j.jhazmat.2019.06.001, PMID: 31326765WibisonoYAgung NugrohoWAkbar DeviantoLAdi SuliantoARoil BiladM.
Microalgae in food-energy-water nexus: A review on progress of forward osmosis applications. Membranes. (2019) 9:166. doi: 10.3390/membranes9120166, PMID: 31817329VolpinFChekliLPhuntshoSChoJGhaffourNVrouwenvelderJS.
Simultaneous phosphorous and nitrogen recovery from source-separated urine: A novel application for fertiliser drawn forward osmosis. Chemosphere. (2018) 203:482–9. doi: 10.1016/j.chemosphere.2018.03.193, PMID: 29635160LiuXTaoYWenGKongFZhangXHuZ.
Influence of soil and irrigation water pH on the availability of phosphorus in struvite derived from urine through a greenhouse pot experiment. J Agric Food Chem. (2016) 64:3324–9. doi: 10.1021/acs.jafc.6b00021, PMID: 27078189KedwellKCChristensenMLQuist-JensenCAJørgensenMK.
Effect of reverse sodium flux and pH on ammoniacal nitrogen transport through biomimetic membranes. Sep Purif Technol. (2019) 217:40–7. doi: 10.1016/j.seppur.2019.02.001, PMID: 41813336SaliuTDOladojaNASauvéS.
Eco-friendly and sustainability assessment of technologies for nutrient recovery from human urine—a review. Front Sustain. (2024) 4:1338380. doi: 10.3389/frsus.2023.1338380, PMID: 41810299TeowYHSumJYHoKCMohammadAW.
Principles of nanofiltration membrane processes. Osmosis Engineering. (2021) pp:53–95. doi: 10.1016/B978-0-12-821016-1.00014-0, PMID: 41813336SuhalimNSKasimNMahmoudiEShamsudinIJMohammadAWMohamed ZukiF.
Rejection mechanism of ionic solute removal by nanofiltration membranes: an overview. Nanomaterials. (2022) 12:437. doi: 10.3390/nano12030437, PMID: 35159781WafiMKHussainNEl-Sharief AbdallaOAl-FarMDAl-HajajNAAlzonnikahKF.
Nanofiltration as a cost-saving desalination process. SN Appl Sci. (2019) 1:1–9. doi: 10.1007/s42452-019-0775-y, PMID: 41810330PronkWPalmquistHBiebowMBollerM.
Nanofiltration for the separation of pharmaceuticals from nutrients in source-separated urine. Water Res. (2006) 40:1405–12. doi: 10.1016/j.watres.2006.01.038, PMID: 16530802MaurerMPronkWLarsenTA.
Treatment processes for source-separated urine. Water Res. (2006) 40:3151–66. doi: 10.1016/j.watres.2006.07.012, PMID: 16949123ZhaoZPXuLShangXChenK.
Water regeneration from human urine by vacuum membrane distillation and analysis of membrane fouling characteristics. Sep Purif Technol. (2013) 118:369–76. doi: 10.1016/j.seppur.2013.07.021, PMID: 41813336TunLLJeongDJeongSChoKLeeSBaeH.
Dewatering of source-separated human urine for nitrogen recovery by membrane distillation. J Membr Sci. (2016) 512:13–20. doi: 10.1016/j.memsci.2016.04.004, PMID: 41813336KhumaloNNthunyaLDereseSMotsaMVerliefdeAKuvaregaA.
Water recovery from hydrolysed human urine samples via direct contact membrane distillation using PVDF/PTFE membrane. Sep Purif Technol. (2019) 211:610–17. doi: 10.1016/j.seppur.2018.10.035, PMID: 41813336XuKQuDZhengMGuoXWangC.
Water reduction and nutrient reconcentration of hydrolyzed urine via direct-contact membrane distillation: ammonia loss and its control. J Environ Eng. (2019) 145:04018144. doi: 10.1061/(ASCE)EE.1943-7870.0001496, PMID: 29515898MercerEDaveyCJAzziniDEusebiALTierneyRWilliamsL.
Hybrid membrane distillation reverse electrodialysis configuration for water and energy recovery from human urine: An opportunity for off-grid decentralised sanitation. J Membr Sci. (2019) 584:343–52. doi: 10.1016/j.memsci.2019.05.010, PMID: 31423048UllahRKhraishehMEstevesRJMcLeskeyJTJrAlGhoutiMGad-el-HakM.
Energy efficiency of direct contact membrane distillation. Desalination. (2018) 433:56–67. doi: 10.1016/j.desal.2018.01.025, PMID: 41813336Munoz-CupaCHuYXuCBassiA.
An overview of microbial fuel cell usage in wastewater treatment, resource recovery and energy production. Sci Total Environ. (2021) 754:142429. doi: 10.1016/j.scitotenv.2020.142429, PMID: 33254845PaucarNESatoC.
Microbial fuel cell for energy production, nutrient removal and recovery from wastewater: A review. Processes. (2021) 9:1318. doi: 10.3390/pr9081318, PMID: 41725453KuntkePŚmiechKBruningHZeemanGSaakesMSleutelsTHJA.
Ammonium recovery and energy production from urine by a microbial fuel cell. Water Res. (2012) 46:2627–36. doi: 10.1016/j.watres.2012.02.025, PMID: 22406284SantoroCLiBCristianiPSquadritoG.
Power generation of microbial fuel cells (MFCs) with low cathodic platinum loading. Int J Hydrogen Energy. (2013) 38:692–700. doi: 10.1016/j.ijhydene.2012.05.104, PMID: 41813336KuntkePSleutelsTHJASaakesMBuismanCJ.
Hydrogen production and ammonium recovery from urine by a Microbial Electrolysis Cell. Int J Hydrogen Energy. (2014) 39:4771–78. doi: 10.1016/j.ijhydene.2013.10.089, PMID: 41813336JangJKangYHanJHJangKKimCMKimIS.
Developments and future prospects of reverse electrodialysis for salinity gradient power generation: Influence of ion exchange membranes and electrodes. Desalination. (2020) 491:114540. doi: 10.1016/j.desal.2020.114540, PMID: 41813336PronkWBiebowMBollerM.
Electrodialysis for recovering salts from a urine solution containing micropollutants. Environ Sci Technol. (2006) 40:2414–20. doi: 10.1021/es051921i, PMID: 16646483WangYKGengYKPanXRShengGP.
In situ utilization of generated electricity for nutrient recovery in urine treatment using a selective electrodialysis membrane bioreactor. Chem Eng Sci. (2017) 171:451–58. doi: 10.1016/j.ces.2017.06.002, PMID: 41813336De PaepeJLindeboomREVanoppenMDe PaepeKDemeyDCoessensW.
Refinery and concentration of nutrients from urine with electrodialysis enabled by upstream precipitation and nitrification. Water Res. (2018) 144:76–86. doi: 10.1016/j.watres.2018.07.016, PMID: 30014981JermakkaJBrewsterETLedezmaPFreguiaS.
Electro-concentration for chemical-free nitrogen capture as solid ammonium bicarbonate. Sep Purif Technol. (2018) 203:48–55. doi: 10.1016/j.seppur.2018.04.023, PMID: 41813336ZhangYAguilaBMaSZhangQ.
Comparison of the use of functional porous organic polymer (POP) and natural material zeolite for nitrogen removal and recovery from source-separated urine. J Environ Chem Eng. (2020) 8:104296. doi: 10.1016/j.jece.2020.104296, PMID: 41813336OteroMFreireLGómez-CuervoSÁvilaC.
Ammonium removal in wastewater treatments by adsorbent geopolymer material with granite wastes: full-scale validation. Cleantech. (2024) 6:339–64. doi: 10.3390/cleantechnol6010017, PMID: 41725453SendrowskiABoyerTH.
Phosphate removal from urine using hybrid anion exchange resin. Desalination. (2013) 322:104–12. doi: 10.1016/j.desal.2013.05.014, PMID: 41813336GuanTKuangYLiXFangJFangWWuD.
The recovery of phosphorus from source-separated urine by repeatedly usable magnetic Fe3O4@ZrO2 nanoparticles under acidic conditions. Environ Int. (2020) 134:105322. doi: 10.1016/j.envint.2019.105322, PMID: 31739135KiniBHariS.
Removal of phosphorus from human urine by adsorption method using GGBS. Int J Civ Eng Technol. (2017) 8:1061–69.
PandianKVijayakumarSMustaffaMRAFSubramanianPChitraputhirapillaiS.
Biochar–a sustainable soil conditioner for improving soil health, crop production and environment under changing climate: a review. Front Soil Sci. (2024) 4:1376159. doi: 10.3389/fsoil.2024.1376159, PMID: 41810299KannanPParamasivanMMarimuthuSSwaminathanCBoseJ.
Applying both biochar and phosphobacteria enhances Vigna mungo L. growth and yield in acid soils by increasing soil pH, moisture content, microbial growth and P availability. Agric Ecosyst Environ. (2021) 308:107258. doi: 10.1016/j.agee.2020.107258, PMID: 41813336XuKLinFDouXZhengMTanWWangC.
Recovery of ammonium and phosphate from urine as value-added fertilizer using wood waste biochar loaded with magnesium oxides. J Clean. Prod. (2018) 187:205–14. doi: 10.1016/j.jclepro.2018.03.206, PMID: 41813336ZhengYWanYChenJChenHGaoB.
MgO modified biochar produced through ball milling: a dual-functional adsorbent for removal of different contaminants. Chemosphere. (2020) 243:125344. doi: 10.1016/j.chemosphere.2019.125344, PMID: 31756657LiJLiBHuangHLvXZhaoNGuoG.
Removal of phosphate from aqueous solution by dolomite-modified biochar derived from urban dewatered sewage sludge. Sci Total Environ. (2019) 687:460–9. doi: 10.1016/j.scitotenv.2019.05.400, PMID: 31212154XiaDTanFZhangCJiangXChenZLiH.
ZnCl2-activated biochar from biogas residue facilitates aqueous As(III) removal. Appl Surf. Sci. (2016) 377:361–9. doi: 10.1016/j.apsusc.2016.03.109, PMID: 41813336ZhangLYangLChenJZhangYZhouX.
Enhancing efficient reclaim of phosphorus from simulated urine by magnesium-functionalized biochar: adsorption behaviors, molecular-level mechanistic explanations and its potential application. Sci Total Environ. (2024) 906:167293. doi: 10.1016/j.scitotenv.2023.167293, PMID: 37742963OtienoAOHomePGRaudeJMMurungaSINgumbaEOjwangDO.
Pineapple peel biochar and lateritic soil as adsorbents for recovery of ammonium nitrogen from human urine. J Environ Manage. (2021) 293:112794. doi: 10.1016/j.jenvman.2021.112794, PMID: 34038825RiechmannMENdwandweBGreenwoodEEReynaertEMorgenrothEUdertKM.
On-site urine treatment combining Ca(OH)2 dissolution and dehydration with ambient air. Water Res. (2021) X:100124. doi: 10.1016/j.wroa.2021.100124, PMID: 34917915DuttaSVinneråsB.
Fertilizer from dried human urine added to ash and lime—a potential product from eco-sanitation system. Water Sci Technol. (2016) 74:1436–45. doi: 10.2166/wst.2016.324, PMID: 27685973VasiljevASimhaPDemisseNKarlssonCRandallDGVinneråsB.
Drying fresh human urine in magnesium-doped alkaline substrates: capture of free ammonia, inhibition of enzymatic urea hydrolysis & minimisation of chemical urea hydrolysis. Chem Eng. J. (2022) 428:131026. doi: 10.1016/j.cej.2021.131026, PMID: 41813336AntoniniSNguyenPTArnoldUEichertTClemensJ.
Solar thermal evaporation of human urine for nitrogen and phosphorus recovery in Vietnam. Sci Total Environ. (2012) 414:592–9. doi: 10.1016/j.scitotenv.2011.11.055, PMID: 22172663CourtneyCRandallDG.
Concentrating stabilized human urine using eutectic freeze crystallization for liquid fertilizer production. Water Res. (2023) 233:119760. doi: 10.1016/j.watres.2023.119760, PMID: 36848853RandallDGNathooJ.
Resource recovery by freezing: a thermodynamic comparison between a reverse osmosis brine, seawater and stored urine. J Water Process Eng. (2018) 26:242–9. doi: 10.1016/j.jwpe.2018.10.020, PMID: 41813336Noe-HaysAHomeyerRJDavisAPLoveNG.
Advancing the design and operating conditions for block freeze concentration of urine-derived fertilizer. ACS ES&T Eng. (2021) 2:446–55. doi: 10.1021/acsestengg.1c00271, PMID: 41799136AlmuntashiriAHosseinzadehAVolpinFAliSMDorjiUShonH.
Removal of pharmaceuticals from nitrified urine. Chemosphere. (2021) 280:130870. doi: 10.1016/j.chemosphere.2021.130870, PMID: 34162101EngelhardtSVogelJDuirkSEMooreFBBartonHA.
Assessment of urea hydrolysis as a pretreatment strategy to improve total nitrogen rejection from urine using aquaporin-based membranes in forward osmosis. J Water Process Eng. (2020) 34:101135. doi: 10.1016/j.jwpe.2020.101135, PMID: 41813336HuangXGuidaSJeffersonBSoaresA.
Economic evaluation of ion-exchange processes for nutrient removal and recovery from municipal wastewater. NPJ Clean Water. (2020) 3:1–10. doi: 10.1038/s41545-020-0054-x, PMID: 41803196TongYMcNamaraPJMayerBK.
Adsorption of organic micropollutants onto biochar: a review of relevant kinetics, mechanisms and equilibrium. Environ Sci.: Water Res Technol. (2019) 5:821–38. doi: 10.1039/C8EW00938D, PMID: 41811194LorickDMacuraBAhlströmMGrimvallAHarderR.
Effectiveness of struvite precipitation and ammonia stripping for recovery of phosphorus and nitrogen from anaerobic digestate: a systematic review. Environ Evid. (2020) 9:1–20. doi: 10.1186/s13750-020-00211-x, PMID: 41810149SaliuTDOladojaNA.
Nutrient recovery from wastewater and reuse in agriculture: a review. Environ Chem Lett. (2021) 19:2299–316. doi: 10.1007/s10311-020-01159-7, PMID: 41810330RenJHaoDJiangJPhuntshoSFreguiaSNiBJ.
Fertiliser recovery from source-separated urine via membrane bioreactor and heat localized solar evaporation. Water Res. (2021) 207:117810. doi: 10.1016/j.watres.2021.117810, PMID: 34741901LyuYAoXChengSLiuNMenYLiZ.
Simultaneous recovery of nutrients and water from human urine by a novel thermally activated peroxydisulfate and membrane distillation integrated system. Chem Eng. J. (2023) 459:141548. doi: 10.1016/j.cej.2023.141548, PMID: 41813336UdertKMWächterM.
Complete nutrient recovery from source-separated urine by nitrification and distillation. Water Res. (2012) 46:453–64. doi: 10.1016/j.watres.2011.11.020, PMID: 22119369SharmaPMutnuriS.
Nutrient recovery and microbial diversity in human urine fed microbial fuel cell. Water Sci Technol. (2019) 79:718–30. doi: 10.2166/wst.2019.089, PMID: 30975938PandorfMHochmuthGBoyerTH.
Human urine as a fertilizer in the cultivation of snap beans (Phaseolus vulgaris) and turnips (Brassica rapa). J Agric Food Chem. (2018) 67:50–62. doi: 10.1021/acs.jafc.8b06011, PMID: 30512939NicastroREl-NakhelCGeelenDFuscoGMDe PascaleSRouphaelY.
Exploring the potential of human urine derivatives in circular agriculture: a case study on lettuce. Front Sustain Food Syst. (2024) 8:1440014. doi: 10.3389/fsufs.2024.1440014, PMID: 41810299SutradharIJackson-deGraffenriedMAkterSMcMahonSAWaidJLSchmidtHP.
Introducing urine-enriched biochar-based fertilizer for vegetable production: acceptability and results from rural Bangladesh. Environ Dev Sustain. (2021) 23:12954–75. doi: 10.1007/s10668-020-01194-y, PMID: 41810330ZapałowskaAJareckiW.
The impact of using different types of compost on the growth and yield of corn. Sustainability. (2024) 16:511. doi: 10.3390/su16020511, PMID: 41725453van MiddenCHarrisJShawLSizmurTPawlettM.
The impact of anaerobic digestate on soil life: a review. Appl Soil Ecol. (2023) 191:105066. doi: 10.1016/j.apsoil.2023.105066, PMID: 41813336ValleSFGirotoASDombinovVRobles-AguilarAAJablonowskiNDRibeiroC.
Struvite-based composites for slow-release fertilization: a case study in sand. Sci Rep. (2022) 12:14176. doi: 10.1038/s41598-022-18214-8, PMID: 35986201Jama-RodzeńskaAGałkaBSzuba-TrznadelAJandyAKamińskaJA.
Effect of struvite (Crystal Green) fertilization on soil element content determined by different methods under soybean cultivation. Sci Rep. (2023) 13:12702. doi: 10.1038/s41598-023-39753-8, PMID: 37543617SrinivasamurthyCAJoshiMSrideviGYogeeshappaHVishwanathS.
Human urine an alternative to chemical fertilizers in crop production. Proc 4th Int Dry Toilet Conf. (2012) pp:22–4.
SrideviGSurendranUSrinivasamurthyCA.
Influence of human urine combined with farm yard manure and chemical fertilizers on french bean and maize cropping sequence in lateritic soils of Karnataka, India. International Journal of Plant Production. (2016) 10:335–46.
YuanXFengYHanCJiangZLiYLiuJ.
A novel approach for enhancing nitrogen and hydrogen recovery from urine in microbial electrochemical gas-permeable membrane system. Sci Total Environ. (2023) 867:161446. doi: 10.1016/j.scitotenv.2023.161446, PMID: 36621490BohMYMuellerTSauerbornJ.
Fertilizing effect of human urine and ammonium nitrate as sources of nitrogen for sorghum [Sorghum bicolor (L.) Moench] under saline conditions. J Plant Nutr. (2021) 44:1957–70. doi: 10.1080/01904167.2021.1884710, PMID: 41799851AshrafMShahzadSMImtiazMRizwanMS.
Salinity effects on nitrogen metabolism in plants–focusing on the activities of nitrogen metabolizing enzymes: a review. J Plant Nutr. (2018) 41:1065–81. doi: 10.1080/01904167.2018.1431670, PMID: 41799851ViskariELGroblerGKarimäkiKGorbatovaAVilpasRLehtorantaS.
Nitrogen recovery with source separation of human urine—preliminary results of its fertiliser potential and use in agriculture. Front Sustain Food Syst. (2018) 2:32. doi: 10.3389/fsufs.2018.00032, PMID: 41810299Beler-BaykalBAllarADBayramS.
Nitrogen recovery from source-separated human urine using clinoptilolite and preliminary results of its use as fertilizer. Water Sci Technol. (2011) 63:811–17. doi: 10.2166/wst.2011.324, PMID: 21330732Akpan-IdiokAUUdoIABraideEI.
The use of human urine as an organic fertilizer in the production of okra (Abelmoschus esculentus) in South Eastern Nigeria. Resour Conserv Recycl. (2012) 62:14–20. doi: 10.1016/j.resconrec.2012.02.003, PMID: 41813336BonvinCEtterBUdertKMFrossardENanzerSTamburiniF.
Plant uptake of phosphorus and nitrogen recycled from synthetic source-separated urine. Ambio. (2015) 44:217–27. doi: 10.1007/s13280-014-0616-6, PMID: 25681979ShingiroCNyagatareGHirwaHSolangeU.
Effect of human urine and compost tea on soil physical and chemical properties case study Rubirizi marshland. J Agric Sci Eng. (2019) 5:61–6.
AdeOluwaOOCofieO.
Urine as an alternative fertilizer in agriculture: Effects in amaranths (Amaranthus caudatus) production. Renew. Agric Food Syst. (2012) 27:287–94. doi: 10.1017/S1742170511000512, PMID: 41694064AmoahPAdamteyNCofieO.
Effect of urine, poultry manure, and dewatered faecal sludge on agronomic characteristics of cabbage in Accra, Ghana. Resources. (2017) 6:19. doi: 10.3390/resources6020019, PMID: 41725453KutuFRMuchaonyerwaPMnkeniPN.
Complementary nutrient effects of separately collected human faeces and urine on the yield and nutrient uptake of spinach (Spinacia oleracea). Waste Manage Res. (2011) 29:532–39. doi: 10.1177/0734242X10374900, PMID: 20601403PradhanSKPiyaRCHeinonen-TanskiH.
Eco-sanitation and its benefits: an experimental demonstration program to raise awareness in central Nepal. Environ Dev Sustain. (2011) 13:507–18. doi: 10.1007/s10668-010-9273-5, PMID: 41810330KassaKAliYZewdieW.
Human urine as a source of nutrients for maize and its impacts on soil quality at Arba Minch, Ethiopia. J Water Reuse Desalin. (2018) 8:516–21. doi: 10.2166/wrd.2018.060, PMID: 41533551SangareDSou DakoureMHijikataNLahmarRYacoubaHCoulibalyL.
Toilet compost and human urine used in agriculture: fertilizer value assessment and effect on cultivated soil properties. Environ Technol. (2015) 36:1291–8. doi: 10.1080/09593330.2014.984774, PMID: 25371046JohansenJLDamMKudjordjieENSantosSSPalmqvistAMagidJ.
Effects of long-term fertilization with contemporary Danish human urine, composted household waste and sewage sludge on soil nematode abundance and community structure. Sci Total Environ. (2023) 860:160485. doi: 10.1016/j.scitotenv.2022.160485, PMID: 36436626AlemayehuYAAsfawSLTerfieTA.
Reusing urine and coffee processing wastewater as a nutrient source: Effect on soil characteristics at optimum cabbage yield. Environ Technol Innov. (2021) 23:101571. doi: 10.1016/j.eti.2021.101571, PMID: 41813336TangFHMaggiF.
Breakdown, uptake and losses of human urine chemical compounds in barley (Hordeum vulgare) and soybean (Glycine max) agricultural plots: Effectiveness of human urine use in agriculture. Nutr Cycl. Agroecosystems. (2016) 104:221–45. doi: 10.1007/s10705-016-9768-z, PMID: 41810330MartinTMEsculierFLevavasseurFHouotS.
Human urine-based fertilizers: A review. Crit Rev Environ Sci Technol. (2022) 52:890–936. doi: 10.1080/10643389.2020.1838214, PMID: 41799851Gómez-MuñozBMagidJJensenLS.
Nitrogen turnover, crop use efficiency and soil fertility in a long-term field experiment amended with different qualities of urban and agricultural waste. Agric Ecosyst Environ. (2017) 240:300–13. doi: 10.1016/j.agee.2017.01.030, PMID: 41813336RoyMASharmaSBrauniusKPAjmaniAMKeyserADButlerCS.
Lime-treated urine improves sunflower growth without shifting soil bacterial communities. Appl Soil Ecol. (2022) 178:104575. doi: 10.1016/j.apsoil.2022.104575, PMID: 41813336WHO (World Health Organization). Guidelines for the safe use of wastewater, excreta and greywater, volume 4: excreta and greywater use in agriculture. Geneva:
WHO (2006).
LahrRHGoetschHEHaigSJNoe-HaysALoveNGAgaDS.
Urine bacterial community convergence through fertilizer production: Storage, pasteurization, and struvite precipitation. Environ Sci Technol. (2016) 50:11619–26. doi: 10.1021/acs.est.6b02094, PMID: 27690126BischelHNDuyganBDÖStrandeLMcArdellCSUdertKMKohnT.
Pathogens and pharmaceuticals in source-separated urine in eThekwini, South Africa. Water Res. (2015) 85:57–65. doi: 10.1016/j.watres.2015.08.022, PMID: 26302215RumeauMPistocchiCAit-MouhebNMarsdenCBrunelB.
Unveiling the impact of human urine fertilization on soil bacterial communities: A path toward sustainable fertilization. Appl Soil Ecol. (2024) 201:105471. doi: 10.1016/j.apsoil.2024.105471, PMID: 41813336BuQWangBHuangJDengSYuG.
Pharmaceuticals and personal care products in the aquatic environment in China: a review. J Hazard Mater. (2013) 262:189–211. doi: 10.1016/j.jhazmat.2013.08.040, PMID: 24036145WangDSuiQZhaoWTLvSGQiuZFYuG.
Pharmaceutical and personal care products in the surface water of China: A review. Chin Sci Bull. (2014) 59:p.743.
FuJWangQWangNLiSZhangHZhuY.
Serum and urinary essential trace elements in association with major depressive disorders: a case–control study. Front Psychiatry. (2023) 14:1297411. doi: 10.3389/fpsyt.2023.1297411, PMID: 38106999Al-FarsiRAhmedMAl-BusaidiAChoudriBS.
Assessing the presence of pharmaceuticals in soil and plants irrigated with treated wastewater in Oman. Int J Recycl. Org Waste Agric. (2018) 7:165–72. doi: 10.1007/s40093-018-0202-1, PMID: 41810330SimhaPBartonMAPerez-MercadoLFMcConvilleJRLalanderCMagriME.
Willingness among food consumers to recycle human urine as crop fertiliser: evidence from a multinational survey. Sci Total Environ. (2021) 765:144438. doi: 10.1016/j.scitotenv.2020.144438, PMID: 33418332MordechayEBMordehayVTarchitzkyJChefetzB.
Fate of contaminants of emerging concern in the reclaimed wastewater-soil-plant continuum. Sci Total Environ. (2022) 822:153574. doi: 10.1016/j.scitotenv.2022.153574, PMID: 35114239RodriguezEEDickmanRKennedyBAgaDNoe-HaysAWiggintonKR.
Comparative exposure assessment of crops grown by urine-derived fertilizer and crops irrigated with reclaimed water. Environ Sci Technol. (2025) 59:13034–41. doi: 10.1021/acs.est.4c12633, PMID: 40536895BarnettANZafarRAkhtarSNabiDArshadM.
Quantification of selected antibiotics in human urine and exposure-response of wheat to environmentally relevant concentrations. J Anim Plant Sci (JAPS). (2025) 35:855–65. doi: 10.36899/JAPS.2025.3.0074MeffeRde Santiago-MartínATeijónGHernandezVMLópez-HerasINozalL.
Pharmaceutical and transformation products during unplanned water reuse: insights into natural attenuation, plant uptake and human health impact under field conditions. Environ Int. (2021) 157:106835. doi: 10.1016/j.envint.2021.106835, PMID: 34450549Sunyer-CaldúAQuintanaGDiaz-CruzMS.
Factors driving PPCPs uptake by crops after wastewater irrigation and human health implications. Environ Res. (2023) 237:116923. doi: 10.1016/j.envres.2023.116923, PMID: 37598843MenacherrySPMKodešováRFedorovaGSadchenkoAKočárekMKlementA.
Dissipation of twelve organic micropollutants in three different soils: effect of soil characteristics and microbial composition. J Hazard Mater. (2023) 459:132143. doi: 10.1016/j.jhazmat.2023.132143, PMID: 37531764KinneyCAVanden HeuvelB.
Translocation of pharmaceuticals and personal care products after land application of biosolids. Curr Opin Environ Sci Health. (2020) 14:23–30. doi: 10.1016/j.coesh.2019.11.004, PMID: 41813336MatilainenAVepsäläinenMSillanpääM.
Natural organic matter removal by coagulation during drinking water treatment: a review. Adv Colloid Interface Sci. (2010) 159:189–97. doi: 10.1016/j.cis.2010.06.007, PMID: 20633865SolankiABoyerTH.
Pharmaceutical removal in synthetic human urine using biochar. Environ Sci.: Water Res Technol. (2017) 3:553–65. doi: 10.1039/C6EW00224B, PMID: 41811194CzechBKończakMRakowskaMOleszczukP.
Engineered biochars from organic wastes for the adsorption of diclofenac, naproxen and triclosan from water systems. J Clean. Prod. (2021) 288:125686. doi: 10.1016/j.jclepro.2020.125686, PMID: 41813336SunPLiYMengTZhangRSongMRenJ.
Removal of sulfonamide antibiotics and human metabolite by biochar and biochar/H2O2 in synthetic urine. Water Res. (2018) 147:91–100. doi: 10.1016/j.watres.2018.09.051, PMID: 30300785JiangJSohnWAlmuntashiriAPhuntshoSWangQFreguiaS.
Feasibility study of powdered activated carbon membrane bioreactor (PAC-MBR) for source-separated urine treatment: A comparison with MBR. Desalination. (2024) 580:117544. doi: 10.1016/j.desal.2024.117544, PMID: 41813336AmmarMYousefEMahmoudMAAshrafSBaltrusaitisJ.
A comprehensive review of the developments in electrocoagulation for the removal of contaminants from wastewater. Separations. (2023) 10:337. doi: 10.3390/separations10060337, PMID: 41725453ShangJGKongXRHeLLLiWHLiaoQJH.
Low-cost biochar derived from herbal residue: characterization and application for ciprofloxacin adsorption. Int J Environ Sci Technol. (2016) 13:2449–58. doi: 10.1007/s13762-016-1075-3, PMID: 41810330ChenTLuoLDengSShiGZhangSZhangY.
Sorption of tetracycline on H3PO4 modified biochar derived from rice straw and swine manure. Bioresour. Technol. (2018) 267:431–7. doi: 10.1016/j.biortech.2018.07.074, PMID: 30032057NiknamEGhahraman AfsharMGhaseminejadHEsamaeilpourM.
Pharmaceutical pollutants removal by using electrochemical oxidation technique. J Water Wastewater; Ab va Fazilab. (2022) 33:71–81. doi: 10.22093/wwj.2022.322888.3220AhmedMBZhouJLNgoHHGuoWJohirMAHBelhajD.
Competitive sorption affinity of sulfonamides and chloramphenicol antibiotics toward functionalized biochar for water and wastewater treatment. Bioresour. Technol. (2017) 238:306–12. doi: 10.1016/j.biortech.2017.04.042, PMID: 28454005YinLMaRWangBYuanHYuG.
The degradation and persistence of five pharmaceuticals in an artificial climate incubator during a one year period. RSC Adv. (2017) 7:8280–7. doi: 10.1039/C6RA28351A, PMID: 41811194HassanSSAbdel-ShafyHIMansourMS.
Removal of pharmaceutical compounds from urine via chemical coagulation by green synthesized ZnO-nanoparticles followed by microfiltration for safe reuse. Arab J Chem. (2019) 12:4074–83. doi: 10.1016/j.arabjc.2016.04.009, PMID: 41813336WeiYZhangMHuSWuDZhaoDLiuH.
Removal of multiple pharmaceutical contaminants from simulated human urine using a reactive flow-through electrochemical membrane. Sep Purif Technol. (2025) 372:133489. doi: 10.1016/j.seppur.2025.133489, PMID: 41813336Paredes-LaverdeMSilva-AgredoJTorres-PalmaRA.
Removal of norfloxacin in deionized, municipal water and urine using rice (Oryza sativa) and coffee (Coffea arabica) husk wastes as natural adsorbents. J Environ Manage. (2018) 213:98–108. doi: 10.1016/j.jenvman.2018.02.047, PMID: 29482094WangLLuoZHongYChelme-AyalaPMengLWuZ.
The treatment of electroplating wastewater using an integrated approach of interior microelectrolysis and Fenton combined with recycle ferrite. Chemosphere. (2022) 286:131543. doi: 10.1016/j.chemosphere.2021.131543, PMID: 34303045Guateque-LondoñoJFSerna-GalvisEAÁvila-TorresYTorres-PalmaRA.
Degradation of losartan in fresh urine by sonochemical and photochemical advanced oxidation processes. Water. (2020) 12:3398. doi: 10.3390/w12123398, PMID: 41725453SebusoDPKuvaregaATLefatsheKKing’onduCKNumanNMaazaM.
Corn husk multilayered graphene/ZnO nanocomposite materials with enhanced photocatalytic activity for organic dyes and doxycycline degradation. Mater Res Bull. (2022) 151:111800. doi: 10.1016/j.materresbull.2022.111800, PMID: 41813336Montoya-RodríguezDMSerna-GalvisEAFerraroFTorres-PalmaRA.
Degradation of the emerging concern pollutant ampicillin in aqueous media by sonochemical advanced oxidation processes: parameters effect, removal of antimicrobial activity and pollutant treatment in hydrolyzed urine. J Environ Manage. (2020) 261:110224. doi: 10.1016/j.jenvman.2020.110224, PMID: 32148294WangFLiuJZhang.JZhouKFengY.
Control and removal of disinfection by-products (DBPs) during electrochemical oxidation of urine. Chin J Environ Eng. (2021) 15:pp.2976–2987.
Cuerda-CorreaEMAlexandre-FrancoMFFernández-GonzálezC.
Advanced oxidation processes for the removal of antibiotics from water: an overview. Water. (2019) 12:102. doi: 10.3390/w12010102, PMID: 41725453KöppingIMcArdellCSBorowskaEBöhlerMAUdertKM.
Removal of pharmaceuticals from nitrified urine by adsorption on granular activated carbon. Water Res X. (2020) 9:100057. doi: 10.1016/j.wroa.2020.100057, PMID: 32566925YangXFlowersRCWeinbergHSSingerPC.
Occurrence and removal of pharmaceuticals and personal care products (PPCPs) in an advanced wastewater reclamation plant. Water Res. (2011) 45:5218–28. doi: 10.1016/j.watres.2011.07.026, PMID: 21864879LiJZhouQCamposLC.
The application of GAC sandwich slow sand filtration to remove pharmaceutical and personal care products. Sci Total Environ. (2018) 635:1182–90. doi: 10.1016/j.scitotenv.2018.04.198, PMID: 29710573RostvallAZhangWDürigWRenmanGWibergKAhrensL.
Removal of pharmaceuticals, perfluoroalkyl substances and other micropollutants from wastewater using lignite, Xylit, sand, granular activated carbon (GAC) and GAC+ Polonite® in column tests – Role of physicochemical properties. Water Res. (2018) 137:97–106. doi: 10.1016/j.watres.2018.03.008, PMID: 29544207DularMGriessler-BulcTGutierrez-AguirreIHeathEKosjekTKlemenčičAK.
Use of hydrodynamic cavitation in (waste) water treatment. Ultrason. Sonochem. (2016) 29:577–88. doi: 10.1016/j.ultsonch.2015.10.010, PMID: 26515938BagalMVGogatePR.
Degradation of diclofenac sodium using combined processes based on hydrodynamic cavitation and heterogeneous photocatalysis. Ultrason. Sonochem. (2014) 21:1035–43. doi: 10.1016/j.ultsonch.2013.10.020, PMID: 24262760WangXJiaJWangY.
Combination of photocatalysis with hydrodynamic cavitation for degradation of tetracycline. Chem Eng. J. (2017) 315:274–82. doi: 10.1016/j.cej.2017.01.011, PMID: 41813336Paredes-LaverdeMCárdenas-JiménezJAPorrasJAcelasNTorres-PalmaRA.
Green adsorbents for pharmaceutics removal from urine: Analysis of isotherms, kinetics, adsorption interactions, cost estimation, and environmental impact. J Environ Manage. (2024) 368:122162. doi: 10.1016/j.jenvman.2024.122162, PMID: 39128352Martínez-EscuderoCMGarridoIContrerasFHellínPFloresPLeón-MoránLO.
Photocatalytic oxidation of carbamazepine in water using TiO2 with LED lamps: Study of intermediate degradation products by liquid chromatography mass spectrometry after dispersive liquid–liquid microextraction. J Photochem Photobiol A Chem. (2024) 452:115551. doi: 10.1016/j.jphotochem.2024.115551, PMID: 41813336Jiménez-BambagueEMVillarreal-AriasDSRamírez-VanegasODGómez-GómezDDMadera-ParraCAPeña-SalamancaEJ.
Removal of pharmaceutical compounds from real urban wastewater by a continuous bio-electrochemical process at pilot scale. J Environ Chem Eng. (2023) 11:110130. doi: 10.1016/j.jece.2023.110130, PMID: 41813336Jiménez-BambagueEMMadera-ParraCARangel-DelgadoMFQuintero-MartinezIMiranda-MosqueraDAristizabal-ApolinarJS.
Photo-Fenton and Electro-Fenton performance for the removal of pharmaceutical compounds in real urban wastewater. Electrochim. Acta. (2023) 442:141905. doi: 10.1016/j.electacta.2023.141905, PMID: 41813336SirinukulwatanaPKunpunyaPSupanivatinPFosterKWThipayaratA.
Hydrogen peroxide-based wet oxidation to eliminate contraceptive hormone residues from pharmaceutical wastewater. In: World environmental and water resources congress (2017)
ASCE Library. p. 167–78.
ShiYZhouLXuYZhouHShiL.
Life cycle cost and environmental assessment for resource-oriented toilet systems. J Clean Prod. (2018) 196:1188–97. doi: 10.1016/j.jclepro.2018.06.129, PMID: 30245554PradelMAissaniL.
Environmental impacts of phosphorus recovery from a “product” Life Cycle Assessment perspective: allocating burdens of wastewater treatment in the production of sludge-based phosphate fertilizers. Sci Total Environ. (2019) 656:55–69. doi: 10.1016/j.scitotenv.2018.11.356, PMID: 30502735LamKLZlatanovićLvan der HoekJP.
Life cycle assessment of nutrient recycling from wastewater: a critical review. Water Res. (2020) 173:115519. doi: 10.1016/j.watres.2020.115519, PMID: 32006809MalilaRLehtorantaSViskariEL.
The role of source separation in nutrient recovery–comparison of alternative wastewater treatment systems. J Clean Prod. (2019) 219:350–8. doi: 10.1016/j.jclepro.2019.02.024, PMID: 41813336SchoenMEXueXWoodAHawkinsTRGarlandJAshboltNJ.
Cost, energy, global warming, eutrophication and local human health impacts of community water and sanitation service options. Water Res. (2017) 109:186–95. doi: 10.1016/j.watres.2016.11.044, PMID: 27888775VidalBHedströmABarraudSKärrmanEHerrmannI.
Assessing the sustainability of on-site sanitation systems using multi-criteria analysis. Environ Sci: Water Res Technol. (2019) 5:1599–615. doi: 10.1039/C9EW00425D, PMID: 41811194HiltonSPKeoleianGADaiggerGTZhouBLoveNG.
Life cycle assessment of urine diversion and conversion to fertilizer products at the city scale. Environ Sci Technol. (2020) 55:593–603. doi: 10.1021/acs.est.0c04195, PMID: 33319997MartinTMAubinJGillesEAubergerJEsculierFLevavasseurF.
Comparative study of environmental impacts related to wheat production with human-urine based fertilizers versus mineral fertilizers. J Clean Prod. (2023) 382:135123. doi: 10.1016/j.jclepro.2022.135123, PMID: 41813336MaizaMVMuñoz-LiesaJPetit-BoixAArcas-PilzVGabarrellX.
Urine luck: environmental assessment of yellow water management in buildings for urban agriculture. Resour Conserv Recycl. (2025) 212:107985. doi: 10.1016/j.resconrec.2024.107985, PMID: 41813336Dos SantosEMBritoDJDACaladoILFrançaAKTLagesJSMonteiro JuniorFDC.
Sodium excretion and associated factors in urine samples of African descendants in Alcântara, Brazil: a population based study. Ren. Fail. (2018) 40:22–9. doi: 10.1080/0886022X.2017.1419967, PMID: 29298567GaoHZhouCLiFHanBLiX.
Economic and environmental analysis of five Chinese rural toilet technologies based on the economic input–output life cycle assessment. J Clean. Prod. (2017) 163:S379–91. doi: 10.1016/j.jclepro.2015.12.089, PMID: 41813336KabdaşlıITünayO.
Nutrient recovery by struvite precipitation, ion exchange and adsorption from source-separated human urine–a review. Environ Technol Rev. (2018) 7:106–38. doi: 10.1080/21622515.2018.1473504, PMID: 41799851LohmanHATrimmerJTKatendeDMubasiraMNagirinyaMNserekoF.
Advancing sustainable sanitation and agriculture through investments in human-derived nutrient systems. Environ Sci Technol. (2020) 54:9217–27. doi: 10.1021/acs.est.0c03764, PMID: 32589417Segrè CohenALoveNGNaceKKÁrvaiJ.
Consumers’ acceptance of agricultural fertilizers derived from diverted and recycled human urine. Environ Sci Technol. (2020) 54:5297–305. doi: 10.1021/acs.est.0c00576, PMID: 32186185TarpehWAWaldIOmolloMOEganTNelsonKL.
Evaluating ion exchange for nitrogen recovery from source-separated urine in Nairobi, Kenya. Dev Eng. (2018) 3:188–95. doi: 10.1016/j.deveng.2018.07.002, PMID: 41813336TrimmerJTCusickRDGuestJS.
Amplifying progress toward multiple development goals through resource recovery from sanitation. Environ Sci Technol. (2017) 51:10765–76. doi: 10.1021/acs.est.7b02147, PMID: 28875704BoyerTHSaettaD.
Opportunities for building-scale urine diversion and challenges for implementation. Acc Chem Res. (2019) 52:886–95. doi: 10.1021/acs.accounts.8b00614, PMID: 30908003MenegatSLedoATiradoR.
Greenhouse gas emissions from global production and use of nitrogen synthetic fertilisers in agriculture. Sci Rep. (2022) 12:14490. doi: 10.1038/s41598-022-18773-w, PMID: 36008570JenssenTKKongshaugG.
Energy consumption and greenhouse gas emissions in fertiliser production. Proc Int Fertiliser Soc. (2003) 509:1–28.
SchreiberTOppermanSHardinRCavicchiJPallmeyerANaceK.
Nested risks and responsibilities: perspectives on fertilizer from human urine in two US regions. J Agric Food Syst Community Dev. (2021) 10:221–42. doi: 10.5304/jafscd.2021.103.016VanderZaagAAmonBBittmanSKuczyńskiT.
Ammonia abatement with manure storage and processing techniques. Costs ammonia abatement Climate co-benefits. (2015), 75–112. doi: 10.1007/978-94-017-9722-1_5, PMID: 41810330TrimmerJTGuestJS.
Recirculation of human-derived nutrients from cities to agriculture across six continents. Nat Sustain. (2018) 1:427–35. doi: 10.1038/s41893-018-0118-9, PMID: 41803196MetsonGSFeizRQuttinehNHTonderskiK.
Optimizing transport to maximize nutrient recycling and green energy recovery. Resour Conserv Recycl X. (2020) 9:100049. doi: 10.1016/j.rcrx.2021.100049, PMID: 41813336RuffattoKEmaminejadSAJunejaAKurambhattiCMargenotASinghV.
Mapping the national phosphorus recovery potential from centralized wastewater and corn ethanol infrastructure. Environ Sci Technol. (2022) 56:8691–701. doi: 10.1021/acs.est.1c07881, PMID: 35617125EchevarriaDTrimmerJTCusickRDGuestJS.
Defining nutrient colocation typologies for human-derived supply and crop demand to advance resource recovery. Environ Sci Technol. (2021) 55:10704–13. doi: 10.1021/acs.est.1c01389, PMID: 34260214IFDC.
International fertilizer development center (IFDC) (2021). Available online at: https://ifdc.org/wp-content/uploads/2022/08/IFDC-Annual-Report-2021-email.pdf (Accessed June 5, 2025).
WildeBCLieberherrEOkemAESixJ.
Nitrified human urine as a sustainable and socially acceptable fertilizer: An analysis of consumer acceptance in Msunduzi, South Africa. Sustainability. (2019) 11:2456. doi: 10.3390/su11092456, PMID: 41725453SimhaPLalanderCVinneråsBGanesapillaiM.
Farmer attitudes and perceptions to the re–use of fertiliser products from resource–oriented sanitation systems: the case of Vellore, South India. Sci Total Environ. (2017) 581:885–96. doi: 10.1016/j.scitotenv.2017.01.044, PMID: 28089535López-RayoSLaursenKHLekfeldtJDDelle GrazieFMagidJ.
Long-term amendment of urban and animal wastes equivalent to more than 100 years of application had minimal effect on plant uptake of potentially toxic elements. Agric Ecosyst Environ. (2016) 231:44–53. doi: 10.1016/j.agee.2016.06.019, PMID: 41813336RutgerssonCEbmeyerSLassenSBKarkmanAFickJKristianssonE.
Long-term application of Swedish sewage sludge on farmland does not cause clear changes in the soil bacterial resistome. Environ Int. (2020) 137:105339. doi: 10.1016/j.envint.2019.105339, PMID: 32036119RosingerAY.
Biobehavioral variation in human water needs: how adaptations, early life environments, and the life course affect body water homeostasis. Am J Hum Biol. (2020) 32:e23338. doi: 10.1002/ajhb.23338, PMID: 31631450RitchieHRoserMOrtiz-OspinaEBeltekianD. Population by five-year age group.
Our World in Data (2023). Available online at: https://ourworldindata.org/grapher/population-by-five-year-age-group (Accessed June 15, 2025).
Nutrien Ltd. Nutrien 2023 fact book.
Nutrien (2024). Available online at: https://nutrien-prod-asset.s3.us-east-2.amazonaws.com/s3fs-public/uploads/2024-01/Nutrien_2023Fact%20Book_Update_12624.pdf (Accessed June 15, 2025).
Edited by: Claude Hammecker, Institut de Recherche Pour le Développement (IRD), France
Reviewed by: Arvind Kumar Mungray, Sardar Vallabhbhai National Institute of Technology, India
Hermes Pérez Hernández, Agriculture and Livestock Research (INIFAP), Mexico
Muhammad Fraz Ali, Northwest A&F University, China