Literature Research / Notes

2003 dry toilet conference Tampere, Finland

The urine you produce annually consist except water of among other things:

  • 5,6 kg nitrogen (N)
  • 0,4 kg phosphorous (P)
  • 1,0 kg potassium (K)

With this amount of nutrients you can fertilize and produce about 200-250 kg corn. It is claimed that one persons urine is enough to fertilize his or her own food.

When urine in one form or another ends up in water it fertilizes different organisms, mainly vegetation and various algae. An abundant amount of nutritious sewage water is one of the reasons why so called blue-green algae (cyanobacteria) and the flowering of algae has increased. It is estimated that the amount nutrients found in one liter of urine is enough to produce about 1 kilogram of algae, provided that all the phosphorus and nitrogen oxides in the urine are used to the maximum.

1st international symposium on ecological sanitation (Closing the loop)

The Mexican model of the urine-diverting toilet represents a modification of the Vietnamese double vault toilet. The urine is diverted and can be used as a liquid fertilizer (approximately 1:5 to 1:10 dilution with water).

Ninety-six percent of what is needed for healthy plant growth is provided by oxygen (45%), carbon (45%), and hydrogen (6%). Elements are required in smaller amounts, such as nitrogen (1.5%), phosphorous (0.15%), potassium (0.15%) and others (0.2%), but they are equally as important as the major elements. In general, green, leafy, non-legume vegetables need more nitrogen than other types of plants. Flowering and fruiting vegetables need more phosphorous, and root vegetables need more potassium.

Nitrogen is needed for leaf and stem growth, and it gives a dark green color to plants. The level of nitrogen added to the soil is important since it affects the plants' access to other nutrients such as phosphorous and potassium. Nitrogen is also important from the point of view of nutrition as it increases the protein content of some foods and feed crops. Phosphorous helps make plants more drought resistant and hardy. It hastens maturity, helps seed and fruit formation, and stimulates root growth. It also helps legumes grow and form nodules. Potassium increases resistance of plants to disease, creates winter hardiness and drought resistance, and produces stiff stalks and stems to reduce water logging. It also increases grain plumpness as well as growth of fruit and root vegetables.

Eighty percent of total nitrogen is excreted in urine (Fig. 16);

and there is 5-7 times more nitrogen in urine than in faeces. Urine contains two-thirds of excreted phosphorous and up to 80% of excreted potassium. These are three major nutrients used in chemical fertilizer preparations.

In Zimbabwe, for example, lime is not added to ecological toilets. There is a strong preference for the addition of a combination of soil and wood ash, which provides the desired effect of pathogen destruction without killing the beneficial organisms in the final product. A period of 3-4 months of decomposition appears to be adequate to reach the quality of product required for agriculture. The resulting humus-like material —processed faeces, paper, soil and wood ash— are normally mixed with topsoil and used for growing vegetables, flowers and trees.

WELL-MANAGED THERMOPHILIC COMPOSTING SYSTEM Part of Chapter 7 of The humanure handbook

Complete pathogen destruction is guaranteed by arriving at a temperature of 62°C (143.6°F) for one hour, 50°C (122°F) for one day, 46°C (114.8°F) for one week, or 43°C (109.4°F) for one month. It appears that no excreted pathogen can survive a temperature of 65°C (149°F) for more than a few minutes. A compost pile containing entrapped oxygen may rapidly rise to a temperature of 55°C (131°F) or above, or will maintain a temperature hot enough for a long enough period of time to thoroughly destroy human pathogens that may be in the humanure (see Figure 7.6). Furthermore, pathogen destruction is aided by microbial diversity, as discussed in Chapter 3. Table 7.14 indicates survival times of pathogens in a) soil, b) anaerobic decomposition conditions, c) composting toilets, and d) thermophilic compost piles.


Novaquatis investigates the possibilities of urine source separation for improved wastewater management better water pollution control with respect to nutrients and micro-pollutants and the possibility of closing the nutrient cycles NOVA 2-2: Precipitation in urine conducting pipes and storage tanks (Dr. Tove Larsen, Dr. des. Kai Udert)

NOVA 2-2 consists of a PhD thesis, which closely investigated precipitation in urine-collecting toilets, waterless urinals, and conventional urinals with field measurements, lab-scale experiments, and computer modeling. The PhD thesis was completed in 2002. The main crystalline compounds of precipitates from urine are struvite, hydroxyapatite, and calcite; the composition depending on the dilution with flushing water. Struvite is the main compound at low dilution, while calcite dominates at high dilution (Udert et al. 2003c, d). A high fraction of phosphate is incorporated into the precipitates. Dilution with tap water increases this fraction by providing calcium and magnesium ions (Udert et al. 2003d). Computer simulations indicate that urine dilution diminishes the precipitation potential – the maximum precipitate concentration – and thus the risk of blockages. Rainwater flushing is more effective than tap water flushing (Udert et al. 2003d). Microbial urea degradation triggers precipitation, which was confirmed with computer simulations. In undiluted urine, a degradation of only 8 % urea resulted in 95 % of the maximum precipitation potential. Urea hydrolyzing bacteria mainly grow in the pipes and are flushed into the collection tank. Few days are necessary for complete urea depletion, and precipitation begins soon after ureolysis has started. Computer simulations based on the surface dislocation approach showed that struvite and octacalcium phosphate are the precipitating minerals in undiluted urine. While struvite precipitates already at low supersaturation, octacalcium phosphate precipitation needs high supersaturation. Octacalcium phosphate is a precursor, which slowly transforms into hydroxyapatite (Udert et al. 2003b).

NOVA 3-1: Since urine contains about 70 % of the nitrogen, 40 % of the phosphorus, 30 % of dissolved organics (DOC), and a large fraction of the hormones and pharmaceuticals from the human metabolism, the potential for reducing the emissions from treatment plants and CSOs is substantial (Larsen et al., 2001).

NOVA 4 is concerned with the processing of the urine solution and the possible production of a fertilizer product. It develops and tests different procedures to stabilize urine, to reclaim the nutrients (N, P, and K), and to eliminate micro-pollutants. A wide variety of elimination technologies for nutrient solutions already exist. However, the adaptation of these technologies for handling urine still needs efforts (<a href="#Larsen_01" class="tlink">Larsen and Boller, 2001</a>; <a href="#Maurer_02" class="tlink">Maurer et al., 2002</a>). Methods to recover nutrients from urine and the elimination of micro-pollutants are the main focus of this research project. Possible technologies are biological processes (e.g. bio film reactors), chemical processes (e.g. precipitation in fluidized bed reactors), and physical processes (e.g. membrane techniques). <br>

<p>Fresh urine solution does not contain any solids and has a slightly acid pH of 6.2 to 6.8. The high amount of biodegradable substrate triggers rapid microbial growth, which strongly alters the chemical composition of urine. One of the dominating reactions is the decomposition or hydrolysis of urea. This microbial catalyzed reaction produces ammonia and increases the pH to above 9. As a consequence the saturation for several phosphate minerals is exceeded and they precipitate. This precipitation can be a nuisance due to possible clogging of pipes (see <a href="NOVA2_e.html"class="tlink">NOVA 2</a>). On the other hand it enables the recovery of phosphorus and some nitrogen as solids.<br>

NOVA 4-1: Additionally, recovered phosphorus can be used as fertilizer or as raw material for the phosphate industry. Basically, there are two possible phosphorus-containing products that can be formed from urine: struvite and calcium phosphate. Investigations are needed to determine whether both products can be formed in practice or whether one of them is favorable. (3)

NOVA -4-2: Fresh urine contains nitrogen mainly in the form of urea, which is a very good fertilizer. However, urea hydrolysis to ammonia and bicarbonate during storage and transport are unwanted reactions. One possible strategy would be to directly treat fresh urine in such a way that urea is conserved. First experiments indicate that this stabilization can be achieved by filtration with micro- or ultra-filtration membranes. This however would imply decentralized treatment, which requires the development of very robust systems. Alternatively, technologies can be developed for the treatment of urine containing ammonia after urea hydrolysis.

NOVA 6, Agriculture: NOVA 6 focuses on agricultural aspects of the NoMix technology. In Switzerland, nutrients derived from human urine could in principle replace around 37 % of the N-demand, 20 % of the P-demand, and 15 % of the K-demand, which are today covered by artificial mineral fertilizers (Lienert et al., 2003). The original purpose of NOVA 6 was to investigate the possibilities and challenges of such a recycling strategy. A number of interesting research questions were formulated: local demand, acceptance and preferences of farmers, risks with respect to micro-pollutants in urine, hygienic aspects, and the environmental consequences of replacing synthetic fertilizers with a urine-based one. Unfortunately, it was not possible to fund the different research projects formulated by EAWAG researchers and external collaborators. Consequently, only a minor project based on a student investigation on the attitude of Swiss farmers towards the NoMix technology has been carried out in 2000 (NOVA 6-1). Possibly, a similar, but more thorough study will be performed later.

NOVA 6-1: How farmers in Switzerland perceive fertilizers from urine: The preferred type of product is a nitrogen fertilizer in form of ammonia nitrate. Most farmers preferred a grainy to a liquid fertilizer and rejected a fertilizer with urine odor. A hazard-free product is absolutely essential: 30 % of all farmers mentioned concerns regarding organic micro-pollutants in additional remarks.

Humanure Handbook

Some of these composting toilets involve the separation of urine from feces. This is done by urinating into a separate container or into a diversion device which causes the urine to collect separately from the feces. The reason for separating urine from feces is that the urine/feces blend contains too much nitrogen to allow for effective composting and the collected material can get too wet and odorous. Therefore, the urine is collected separately, reducing the nitrogen, the liquid content, and the odor of the collected material.
An alternative method of achieving the same result which does not require the separation of urine from feces does exist. Organic material with too much nitrogen for effective composting (such as a urine/feces mixture) can be balanced by adding more carbon material such as sawdust, rather than by removing the urine. The added carbon material absorbs the excess liquid and will cover the refuse sufficiently to eliminate odor completely. This also sets the stage for thermophilic composting because of the carbon/nitrogen balancing.

Urine separation-NOVAQUATIS project

Breeding algae on urine

Every 1000 kg of algae concists something about 500 kg carbon. In other words 1800 kg of CO__2__ (page 9)

Verwijdering van N en P uit effluenten en conditionering tot de vereiste waterkwaliteit voor hergebruik is blijkens het project technisch en economisch haalbaar met het ontwikkelde systeem. Toepassing voor (na)zuivering van effluenten kan een impuls krijgen door de EU Kaderrichtlijn Water en de voortdurende aanscherping van de normen voor lozing op oppervlaktewater. Belangrijke onderwerpen voor vervolgontwikkeling zijn het verminderen van de seizoensafhankelijkheid en het optimaliseren van de waterzuiveringsfunctie. (page 4)

De inzet van biomassa als hernieuwbare grondstof in de industrie en als brandstof in de energiesector kan een belangrijke bijdrage leveren aan reductie van de CO__2__ emissies. De teelt van micro-algen biedt hiervoor een goed perspectief door de tot 5 maal hogere productie t.o.v. landgewassen en de hoogwaardige samenstelling van de biomassa. Micro-algen zijn ééncellige fotosynthetische micro-organismen (Figuur 1.1) die worden gekweekt in open vijversystemen of gesloten kweeksystemen die worden aangeduid met de term “fotobioreactoren” De kweek van micro-algen kan plaatsvinden met eenvoudige inputs: energie uit zonlicht, CO__2__ uit restgassen en water van lagere kwaliteit (effluenten) als bron van voedingsstoffen. De teelt in waterig milieu maakt –door de goede oplosbaarheid van CO__2__ in water– directe toevoer mogelijk van CO__2__ uit rookgassen, die door de algen wordt opgenomen en vastgelegd in nuttig toepasbare biomassa [1]. Dit kan “credits” opleveren voor de handel in CO__2__ emissierechten1. Micro-algen zijn daarnaast in staat stikstofverbindingen (NH__4__+, NO__3__-) en fosfaat tot zeer lage restconcentraties (< enkele 10-tallen mg/l) uit effluenten te verwijderen. (page 9)

Figuur 1(page10)

Gebruik van gehele biomassa als humaan voedingssupplement, in diervoeders, als voedingsbron voor aquacultuur, als bodemverbeterend middel of als grondstof voor bioplastics. De aanwezigheid van specifieke inhoudstoffen (kleurstoffen, vetzuren, bio-actieve stoffen, eiwit) biedt functionele meerwaarde voor deze toepassingen, die een marktwaarde hebben tot enkele 10-tallen €’s per kg droge biomassa.

Beschrijving geven van de HARP (High rate algal pond) en fotobioreactoren om zo een beeld te schetsen op wat voor manieren tot nu toe algen industrieel werden gebruikt. (page 11)

Een aandachtspunt voor het bedrijf is de initiële fase waarin de algen zich aanpassen aan het lichtklimaat en mengregime in de kolom. Bij de kweek van Synechococcus sp. in de zomer van 2002 trad schade op aan de cellen door de hoge lichtintensiteit (en de hoge temperatuur) die leidde tot instorting van de cultuur. Een vergelijkbare adaptatiefase (naar relatief hoge lichtintensiteit en gewijzigde menging) doet zich voor bij de overgang van de fotobioreactoren naar de open cascade. Maatregelen om die adaptatie te faciliteren dienen nader te worden onderzocht. (pagina 17)

De inzet voor waterzuivering werd onderzocht via de kweek van 3 algensoorten in verschillende typen effluenten van een suikerfabriek en een bierbrouwerij. De meeste effluenten blijken geschikt voor algenkweek, waarbij een vergaande verwijdering van N-verbindingen en fosfaat kan worden bereikt. Door menging van verschillende typen afvalwater van één bedrijfslocatie kan de fosfaatverwijdering worden geoptimaliseerd, zoals door UvA is bevestigd in een korte pilot studie. (page20)

Flocculatie/sedimentatie (Case 6) verdient nadere aandacht vanwege het lage energiegebruik en de lage kosten. Sedimentatietests op lab schaal leverden goede resultaten op. Op pilot schaal leek de beheersbaarheid (te) beperkt. Voor vervolgontwikkeling dient de aandacht uit te gaan naar een betere procesbeheersing. (page 21)

De ontwikkeling richt zich op nutriëntverwijdering uit effluenten tot een voldoende kwaliteit voor hergebruik. Micro-algen zijn in staat stikstofverbindingen (NH__4__ +, NO__3__-) en fosfaat tot zeer lage concentraties (< enkele 10-tallen mg/l) uit effluenten te verwijderen door een hoge opnamecapaciteit en affiniteit voor deze nutriënten. In eerder onderzoek kon NH__4__ + volledig worden verwijderd uit een effluent van bietsuikerproductie (NH__4__ + 30 mg/l), met gelijktijdige CO__2__ vastlegging uit rookgas. Bij een algenproductie van 30 ton droge stof/ha.jaar kan 0,45 ton P en 2,1 ton N worden vastgelegd. De waterzuiveringscapaciteit van het systeem is geraamd op basis van het N en P gehalte van representatieve effluenten uit de suikerproductie, bierbrouwerijen en een gemiddelde samenstelling van effluenten uit de agro-industrie. De optimalisatie van de zuiveringscapaciteit en het verminderen van de seizoensafhankelijkheid zijn belangrijke onderwerpen voor de vervolgontwikkeling.(page22)

Houden wij (van) onze spoeltoilet?
Pathogenen bevinden zich met name in de fecaliënstroom. In urine worden nauwelijks pathogenen aangetroffen door het hoge ammoniakgehalte en de lage pH. (page 26)

Ureumcyclus (Dutch)

Ureum of carbamide (NH__2__CONH__2__) , het diamide van koolzuur , is een bijzondere stabiele verbinding met sterk polaire eigenschappen . De oplosbaarheid van ureum in water is erg groot. ( 1080 gram per 1 liter bij 20 graden Celcius )

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