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The Stockholm Environment Institute conducted experiments and collected data that shows the usefulness of a resource every one of us has access to — urine. When utilized as a fertilizer, urine can provide an alternative to chemical fertilizers. The impacts ripple far beyond the nutrient value of the urine; in developing regions, diverting a urine waste stream to fertilizer has a significant economic value. These benefits can easily be recognized at the individual level, and scale all the way up to industrial operations.

Nutrient value

95% of the 0.8-1.5L of urine each person produces per day is water, but the last 5% is comprised of both the macro-nutrients all gardeners are familiar with — Nitrogen (N), Phosphorous (P), and Potassium (K) — as well as some trace micro-nutrients. While the actual content will vary slightly depending on your diet, your urine is generally a well balanced nitrogen rich fertilizer straight out of your body. The average person produces enough urine per year to cover 300-400 m2 of land to a level of 50-100kg/ha of nitrogen.

Some of the yearly values of the nutrients are:

  • 3.5kg of nitrogen
  • 0.5kg phosphorus
  • 1.0kg potassium
  • 0.5kg sulfur
  • 40g magnesium
  • 100g calcium

A family of four can produce the equivalent of a 50kg bag of NPK fertilizer from urine alone every year. This urine has a 10:1:4 ratio of nutrients. This shows a higher nitrogen content than many mineral fertilizers and can be expressed in the lower P/N and K/N ratios of urine. Another positive effect of using urine is that the phosphorous is in a plant usable form, requiring no additional processing before it can be absorbed. The concentration of nutrients in the water can be diluted or concentrated with either drinking more fluid or sweating. This will not have any effect of the total nutrient content and can be diluted just prior to application with water. There is no good reason to concentrate urine destined for use as fertilizer.

How to use

Once collected, urine can either be stored or applied immediately. The application can be done in a variety of spreading methods. The most basic application would be to use a watering can. You can choose to dilute the urine anywhere from 1:1 to 1:15 with water, the most common being ~1:5, or apply it straight. Take care to apply the urine directly to the soil, avoiding foliar feeding the leaves and fruits. To aid in the absorption of the urine it is suggested to dig a small amount of soil up around the leaf perimeter and pour the urine there. Afterward push dirt back over to cover the urine.


Application of diluted urine in early stages of cultivation
Photo: Linus Dagerskog

It is best to apply the urine directly to the soil. This acts as another safety barrier as well as prevents the plants from being burned. Urine applied by foliar feeding, direct application to the plant, will often burn your plants. It will not kill them or do any unrepairable damage, but it is still advised to apply the urine directly to the soil. Some plants are sensitive to the high nutrient content in urine and may burn even if you apply directly to the soil. In the case of tomato plants, which are sensitive to urine, it is best to apply the urine by digging a small trough around the drip line of the plant. The drip line is generally as far as the roots reach; applying the urine here will allow the plant to take what it needs from the peripheral area without burning. As always, if the urine seems too strong for your application, try diluting it just before applying. Dilute as close to application as possible; do not dilute prior to storage.

Other ways to spread the urine are with an irrigation system or animal slurry distribution systems. If irrigation is used, it is advised to flush the lines with water after the urine is applied. This prevents any deposits from building up and clogging the irrigation line. No matter what method of application is chosen, urine should be applied just before it rains or at the end of the day if possible. This is more important in arid areas where evaporation could lead to salt buildup in the soil, but will be beneficial in all regions. If rain is frequent, applications can be increased.

If urine is applied to the soil with little or no storage time, it will break down better and faster than if stored in tanks. This is the preferred use, but only for family farms. The soil, along with its diverse organisms, allows for faster aerobic breakdown of the pollutants picked up in the system. The UV light from the sun also helps hasten the breakdown process — up to 50,000 times more degradation! If an entire community is involved in the urine reclamation, it becomes safer to store the urine.

Handling

For the single family using urine as fertilizer, the handling is very simple. A urine diverting toilet is a great way to make collection painless, but for the developing world some jerry cans are all that is needed. Urine diverting toilets built in Niger have shown to pay back the construction cost when valuing the urine collected as fertilizer, in just under 2 years. The single family does not need to worry about cross contamination as much as a community and therefore is not required to store the urine for as long to make it “safe”. As previously mentioned, urine can be applied directly, without storage — just fine at the family level. These rules are also true for urinals, which have very low cross contamination rates with faeces. It only becomes necessary to store it longer when dealing with large numbers of urine sources. To be extra safe, families can store their urine for 1-4 weeks.

For large community collection several other measures are required. When first implementing any system like this, it is best to contact and involve the farmers that will be using the urine. By involving them you can meet their needs as well as potentially allow them to get involved in the collection process, creating a small income stream for the farmer.

After collecting urine from multiple sources, storage to kill pathogens is required. Large meter cube storage containers are often utilized for their low cost and high availability. If these are not available, jerry cans can be used through the entire process. 20L jerry cans are extremely common. Each 20L container can cover between 4 and 20 square meters of land. These containers are often two colors to indicate their storage life. A yellow container denotes the urine is still in storage, while a green container denotes liquid fertilizer, or birg-koom. Storage time for urine collected from many sources is suggested between 1 and 6 months. The colder the temperature the longer it will take for the pathogens to die down. Ambient temperatures in warmer climates should look toward 1-2 months storage and as the climate gets colder, increase storage time. Make sure not to dilute the urine prior to storage, most commonly with gray water from the sink, or it will take longer for the pathogens to die. Stronger urine is a much harsher environment. Additives and even just a handful of compost are being studied to aid in the breakdown of pathogens as well as increase the nutrient content of the urine. These studies look promising, but have not been published as of yet.


Yellow container for fresh urine,
green container for stored urine to be sold to farmers.
Photo: Linus Dagerskog

One thing to watch out for with the long term storage of urine is the crystallization of phosphorous. The crystals form on the walls of the containers, but can be broken up easily by stirring the urine occasionally. These same crystals can also end up clogging pipes and irrigation lines if not taken care of. For pipes and lines, simply run fresh water through after each urine application.


Storage of urine in one cubic metre tank
Photo: Anna Richert

Safety

While urine is not very dangerous, some precautions should be take to ensure safety. The World Health Organization (WHO) has developed a barrier system to prevent the spread of any disease. The barrier system is quite basic and requires no special skills or tools.


The multi-barrier approach

The first barrier in the WHO process is source separation. This happens at the household level where urine and faeces are separated by a urine diverting toilet. After that, the urine is collected and stored. Everyone involved in handling the urine should wear rubber shoes and gloves. The third barrier is the application technique: applying the urine directly into the soil, preventing it from getting on the above ground parts of the plant. Fourth is selective application. For example, fast growing greens like lettuce are not the best targets for urine fertilizer because they grow and are consumed so fast.


Risk levels in relation to crop and handling strategy

Next is the withholding period barrier. No crops should have urine applied at least a month before harvest. This applies to all kinds of fertilizers, not urine specifically, but it is none-the-less another barrier. The fifth barrier is the gloves and boots, which should be used at all times during urine processing and application. Lastly, hands should be washed frequently when handling urine and all crops should also be washed prior to consumption.

Another safety concern is how urine is stored. Use only sealed containers, otherwise you risk mosquitoes breeding. While urine is fairly sterile when it is fresh, there are some organisms that are alive in it. These will break down when applied to the soil usually, but the storage process is what makes sure these organisms are all dead. One such organism that can live in urine is Salmonella typhi/paratyphi, although it is short lived — requiring only 1 week of storage to reduce their numbers one thousand times.

Cross contamination from faeces is probably the largest concern. While this is not the end of the world, the likelihood of harmful organisms surviving past the application point is higher. Diarrhea is an exception and should be watched for carefully as it is a source of bad contamination.

Again these safety concerns all but disappear at the family level. Family members are more likely to transmit diseases directly to the other members of the family than through urine. The health risks at the family level are very low. Urine can be applied fresh, in its near sterile form as previously mentioned, to allow for aerobic and UV breakdown.

When these safety concerns are compared to using pesticide and animal antibiotics, you are actually at a far less risk of transmitting diseases via urine than you are using “modern” substances and techniques. Urine fertilizer has shown lower heavy metals than waste or sludge water and even farmyard manure. The chemicals introduced through the consumption of pharmaceuticals are much worse, and not properly treated, even in most first world countries. When working with local urine, and even more-so when dealing with a family, your chemical loop will be closed. Only the chemicals you have taken will be present in your urine; no outside sources are used as input. Menstrual blood in the urine has no negative health impacts and can be used normally.


Components of urine collection system Ouagadougou, Berkina Faso
Photos: CREPA

Economics

In developing nations where resources are scarce, being able to produce your own fertilizer can go a long way to economic sovereignty. In Burkina Faso the value of a 20L container of urine is about 25 US cents. The farmers in Burkina Faso can often only afford to purchase one bag of fertilizer per season at a cost of 6-7USD. By harvesting their urine and using it as a fertilizer the farmer can create the equivalent of two bags worth of fertilizer for little to no economic input. The cost of purchasing the chemical fertilizer is also retained, further reducing economic stress.

The economic value can multiply quickly as you scale up to a village-sized collection system. This has side effects of producing jobs all through the cycle from collection, to tracking storage, to sales, and many others. As valuable as this is for the local village, reducing the need for external chemical fertilizers, it is not without its shortcomings. The collection cost of running a urine storage/distribution facility is currently greater than the industrial value of the urine when compared to other fertilizers.

Yield

The true benefits of the system can be seen in the increased yields. In terms of sustenance farming, there is little else to be said. Larger crops mean more income for the farmer, and more food for the community. While the test crops were not measured with scientific rigor, it is clear that the urine treated crops out produced non treated crops.


Field trials from Niger. Urine fertilised millet to the right.
Photo: Linus Dagerskog


Urine fertilised sorghum to the left
Photo: Linus Dagerskog


Spinach (Swiss Chard) fertilised with urine, left.
Photo: Peter Morgan

Conclusion

Urine is a valuable resource that should be harvested more widely. In the developing world, this built-in fertilizer stream is low hanging fruit on the road out of poverty. With even a minimal investment, a family or sustenance farmer can not only reduce their need for importing synthetic fertilizers, but can also reclaim a waste stream. The beneficial impacts stretch far beyond the urine diverting toilet.

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14 Responses to “Urine: Closing the NPK Loop”

  1. fred and mary

    Thanks for a great article! I bought a book, Liquid Gold, several years ago and have been collecting my urine in a urinal (like used in hospitals) for a couple of years to use as fertilizer and a great compost activator if used full strength. Also pour it straight (full strength) on our sheet mulching areas to help break down leaves and other organic matter we place over the cardboard to make beds ready for Spring planting. Only problem is that I cannot get my wife to use her urinal.

    Reply
    • Sarah

      As a house full of women using urine on the garden and it’s collection seemed unappealing. Anything that involved squatting or getting it on your hands by holding something in the collection area… Ick. however a female friend came up with a simple low cost urine collector and separator. She just put a plastic container inside the toilet bowl. With a bit of experimentation she found the best container was a catering size margarine container. In New Zealand they are a tall square container made of sturdy plastic that is almost as wide as the bowl. The square shape seems to hold it well in the toilet. Because it’s tall you can flush around it. The corner on the square container creates an easily directed pour for putting it in our watering can for dilution. It’s working for us :-)

      Reply
    • ian

      I have been using urine as the main fertilizer in a hydroponics system for two years. Its ok but not perfect. After reading this may add some P and K to the water pool.

      Reply
  2. Sergi

    This is an excellent article and thank you Mark. Extremely practical and of particular importance for both the ‘developed’ and ‘developing’ world

    Reply
  3. Adam T

    One major concern this article has only briefly mentioned is the contamination of urine with prescription medicines. Popular hysteria concentrates on antibiotics, but the greater long term problem is with oestrogens (originating from the pill), antipsychotics, antidepressants and countless other drug molecules which are also excreted in urine. US studies of river water show that even after sewage treatment these drugs can still be released in the water, and have subsequently been found in the tissue of fish and other aquatic life. Oestrogens have especially contributed to sexual malformations in amphibians. Evidently there are drug molecules that are resistant to biodegradation (chemical recalcitrance*) so you should consider that before you add urine into your food chain. (As a point of interest, many antibiotics are easily degraded and don’t last long in the environment).

    Pros:
    -In the less developed world where people are less likely to have access to prescription medicines, the use of urine can be justified (however disease management becomes the priority).
    – Indeed the use of urine closes the NPK loop, and where possible we should really return the fertility back to the fields provided that fertility doesn’t harbour long term contaminants.

    Cons:
    – Due to medical confidentiality, some people will prefer to keep their medical conditions private even with family members, and they are entitled to. This presents the problem that you will never know whether the urine is truly clean of pharmaceuticals.
    – No guest is going to surrender their private ailments and medication list to their host, and so there’s another complication if they need to use the household bathroom.
    – The use of urine as fertiliser is probably less feasible in the developed world due to these reasons. If its use is insisted on, then perhaps including it in hot composting can reduce the risks. Both heat and microbial degradation will help to reduce soil contamination. Risk management is ultimately up to the individual.

    *Reference: MICROBIOLOGY 4th Edition- Prescott, Harley, Klein.

    Reply
  4. Harry Harrison

    Crazy that we are treating sewage and still releasing chemical contaminants. Another good reason not to take prescription or other drugs tho in reality it’s rampant.
    My understanding is that many of the “hormonal” changes seen in wildlife are related to organophosphate pesticides which may mimic the molecular structures of hormones.
    Natural oestrogenic compounds are not uncommon in plants. Subterainian clover is one example of many. Progesterones also used for the pill are common in plants. Are the natural forms more readily biodegraded?
    There is a plethora of other drugs which may be more harmful at low levels particularly immunomodulators used in chemotherapeutics.

    Reply
  5. Mark Feineigle

    Adam T, many US water treatment facilities specifically do not even treat for many of the chemicals you’ve listed. If you drink tap water in the US, you are most likely exposing yourself already.

    Disease management is not a problem; storage times of 1-6 months will kill all pathogens. For a deeper analysis, see the Practical Guidance on the Use of Urine in Crop Production (1.6mb PDF) linked at the bottom of the article.

    If the collection and treatment is occurring in the developed world on an industrial scale, it would be treated for pharmaceuticals during the storage phase. If it is occurring in the developed world at the home scale, the residual in the urine from medication could be an issue. I would wager the plants won’t actively take in the bad chemicals as long as the soil is fertile, if the buildup from a single family would even be enough to warrant concern.

    In the developed world, you are right there is very little concern for medical contamination at either the industrial or family level. Again, disease management is a very small concern at both the family level, where you are more likely to spread disease person to person, and on the industrial level, where long storage times assure total pathogen destruction.

    Reply
  6. jennie

    If you like this idea, you can also try using urine for your laundry – by the way, it does get rinsed out in the end if that is your concern – and it has been used by the Eygptians, Romans and East Indians for centuries to clean laundry. I do it – and have clean and fresh-smelling clothes and a cleaner concience for it.

    Reply
  7. Adam T

    Good points you’ve raised Harry and Mark. Until water treatment improves then i wouldn’t want to consume anything that has grown in that water. Luckily most of the potable water in Melbourne, Australia comes from mountain reservoirs and treated water is released back into the bay near some estuaries. Admittedly i know little about how well treated it is. Filtering water through activated charcoal is actually a good way to remove many chemical impurities if you are concerned about ingesting chemicals in your tap water (esp around the Great Lakes region).

    To answer Harry’s question about natural hormones, yes they would be more readily degraded, the rough general rule is that bacteria have a harder time breaking larger more complex molecules. My concern about hormones isnt so much about the plants taking it up, its more about the soil life, worms and insects etc that ultimately end up in the chickens and their eggs that supply my family.

    I’m a pharmacist by trade(hence the interest in biochemistry) and have a love of sustainability. I practice permaculture myself, but I’ve simply identified some concerns i would have in my previous response with contaminants in urine. Personally i refrain from taking medicines unless required, but it’s also part of my profession to understand that many people require pharmaceutical help and that its not feasible to avoid them altogether.

    My system at home includes chickens and quite a few ponds with many types of aquatic life. Any pharmaceutical presence will be directly relayed back to my family via the chickens and also contaminate the ponds and treasured native frogs. This is an important point for those interested in aquaponics. Amphibians and fish are a very sensitive lot, and Harry you are correct about organophosphates, medicines arent exclusively the only lot affect them. I would come to the conclusion that the use of urine in food crops is best for the undeveloped world where pharmaceutical intrusion is at a minimum.

    Reply
  8. MarkB

    Multiple problems… If you’re going to use urine as your only fertilizer, it’s unbalanced – the nitrogen level is too high. If you’re going to add P and K to make up for the imbalance – how much? And fertilizer with P and K but no N is considerably more expensive than standard N-P-K mixes.

    If you store urine to kill off pathogens, your nitrogen is going to convert to ammonia and disappear into the atmosphere. So much for recycling all that nitrogen.

    If you store urine, you absolutely will get precipitate on the inner walls of your container. Some is protein and some is your plant nutrients. Try saving urine in a clear milk container for a few days and you’ll see it.

    If you have to avoid getting it on the plants, it’s obviously harsh chemically. Worried about ‘chemicals?’ Worry about ‘natural’ urine – it’s full of them.

    “No crops should have urine applied at least a month before harvest. This applies to all kinds of fertilizers,”

    That’s just bizarre. You shouldn’t use PESTICIDES on plants just before harvest – not fertilizer.

    I use Urine on my lawn. I don’t eat grass, and I don’t buy lawn fertilizer, so there’s no down side for me. I also add urine to carbon-heavy compost piles early in the process. In each case, I avoid the problems I’ve cited. In Africa, I’m sure it’s a good idea, but let’s not confuse Africa with Western gardens – totally different situation.

    Reply
  9. Gil

    @ MarkB:

    Your point two is an answer for your first point. If there is too much N, just let go some of that ammonia… As for “So much for recycling all that nitrogen” Why so pessimistic? Would you suggest not to bother then recycling the other nutrients? The N would be lost anyway not using the urine.

    See link: “Good availability of nutrients is important in the early stages of cultivation, though once the crop enters its reproductive stage nutrient uptake diminishes. From a health perspective this is good since increased time between application and harvest decreases risk of pathogen transmission. A waiting period of one month between fertilization and harvest should always be observed.”

    Why would you suggest to keep on fertilizing until harvest? Not very efficient fertilizer use if you ask me, check (scientific) literature.

    I think the whole idea about using urine as a fertilizer, is that as opposed to how it is treated, urine should not be seen as a waste product, but as a resource that would close the nutrient cycle. In that perspective it doesn’t matter if you live in Afrika or any Western country, it remains a waste of valuable resource we prefer to compensate with costly, non-environmental and unsustainable synthetic fertilizers.

    I agree you should be critical, but this doesn’t mean you should burn down genuinely good ideas/initiatives just for the sake of being critical. Rather present some ideas on how to overcome potential ‘multiple problems’…

    Reply
  10. Andrew

    Sometimes you can over complicate something very simple.

    When you’re talking about a home garden…

    If ONE male member of the household is urinating in a 20 litre plastic bucket (half filled with water) with a lid and then emptying that onto selected plants (eg fruit and productive trees) and:

    # The trees have a good layer of fine mulch…

    # You throw the odd banana peel or a modest sprinkling of ashes in the bucket…

    # The person doing the urinating is mainly eating a diet high in fruits and vegetables out of the garden, drinking plenty of water and is not taking drugs…

    # And you’re careful about fertilizing a lot of trees this way so the trees get a rest between fertilization…

    Then all the risks mentioned are so tiny they’re laughable. Some of the risks mentioned are eliminated altogether.

    You can get carried away with implementing ideas on a huge scale (collecting the urine of hundreds of people to use on a farm for example) when often the micro scale (one person fertilizing a home garden) makes a whole lot more sense.

    Reply
  11. Amanda

    I’ve been using urine directly on my garden beds for some time, some plants I fertilise in winter, some in spring, some in autumn. I agree that it can all get ‘too complicated’- go with instinct. I like to think i facilitate the building of diverse, health soil webs, and that they are capable of breaking down complex chemicals. If you are paranoid about your annual crops then use on longer establishing trees and soils, and more fungal based soils. I think we should have a little more faith in the ability of nature. We know the unavoidable chemical burden of the world we have created of our lifestyles (hello VOCs and the rest.) We all want to live in a clean world, but let’s do the best we can with what we can. As a nutritionist/ naturopath, going back to growing good food via permaculture is about closing the loop for me also. Good nutrition is protective. Lack of nutrition leads to disease. If I can grow wholesome food it will go some substantial way to protecting me against other chemical imbalance. I’d rather pee on the broccoli than justify the digging of a great dirty hole in QLD then ship all that phosphorous thousands of kilometres down here. no brainer.

    Reply
    • Steven e

      Well put Amanda! So many things to over think, but i too have found out that most of that thinking is fruitless and that things tend to work themselves out pretty well if we just ignore most of the excess of information that we could worry about excessively and just see what happens. We are better off judging by how our gardens thrive or fail to thrive, rather than some theoretical information we picked up somewhere. I’ve been using the stuff for well over a decade with excellent results. At first I was cautious, but then I started to be more bold which taught me what the limits actually were rather than what someone else said. I recently wrote a blog post trying to dispel the many common myths about using urine as a fertilizer that are so prevalent and to encourage open experimentation rather than this sort of conservative fear based approach that is so common. This article here iis really excellent in general and doesn’t promote any of that “common knowledge” that is holding people back. I also like your idea that you are supporting the web of life down there. People are literally afraid that they are going to kill the soil life with a soluble fertilizer, or too many salts, or all sorts of worries. Thats all theoretical. When you see the spot you peed on has grass that is deep vibrant green and 1000 times bigger than the grass next to it, that should tell you something. I do no dig gardening for the most part and having that soluble fertilizer is what makes it all work so well. If anyone out there is on the fence, just do it and see what happens. Or go read my post 10 yellow terrors and have a laugh at me mocking your fears, and then just do it ;)

      Reply

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