Saturday, January 25, 2014

Ecological Sanitation. Reconnecting the Loop. Recycling Nitrogen. Urine as Fertilizer. 1.25.14

I've been debating whether to include this topic in my blog.  There is a weirdness factor.   Difficult to dismiss.  It's also difficult to locate much information about ecological sanitation.  Especially, most articles concentrate on the gee-whiz factor, puns, and what various authors call the "ick factor".  In many articles, serioius data is missing, and the authors concentrate on silly euphemisms.  In web fora, the majority of commenters seem to have little information or expertise, just opinions.

Addressing the weirdness factor, via rational analysis of the issues, is the main reason for the length of this blog post.  Ecological sanitation, or eco-san, is the utilization of human waste for fertilizer.  In this case, human urine.  Other waste is a different kettle of fish, and I'm not discussing that.  This blog post discusses eco-san as applies in horticulture, for home garden, homestead, or permaculture.

Even with cultural disdain, I think this topic is important.  In a world of decreasing resources, increasing environmental damage, profligate waste, expensive horticulture and agriculture, and separation of human life from nature's cycles or web, any topic that addresses rational environmental stewardship, rationally, should be approached.  Voltaire said, "No snowflake in an avalanche ever feels responsible."  That applies here as well.  Each person is responsible for waste and pollution they could otherwise prevent.

The main gardening fertilizer ingredient is "fixed" nitrogen.  That means, nitrogen that has been removed from gaseous form, and converted to a form that plants can use.  Historically, fixed nitrogen came from soil, decaying plants, and nitrogen content from animal waste, especially animal urine.  Soil bacteria converted fixed nitrogen into forms that plants could use.  The plants converted the nitrogen to plant substances, especially protein.  Humans harvested the protein-containing fruits, leaf tissues, tubers, stems, and seeds.  The nitrogen from those materials was digested, and most excreted as urea, in urine.  Much less went into feces.  That urine went into the ground, then into ground water, or rivers, or was fermented and converted into gas, lost into the atmosphere.

Nitrogen cycle.  This chart does not include urea, which bacteria rapidly convert into ammonium.  Image source:  wikipedia.

In most settings, usable nitrogen availability is the major limitation for plant growth.  Fertilizer nitrogen us used to boost growth of plants in farming and gardening.  Other nutrients or factors (pH, sun, heat, water) can be limiting, but nitrogen fertilizer is a major issue.

For a while, there were mines - usually of guano, which was made by birds or bats, accumulated in such vast amounts that it was mined and sold for agricultural use.  When guano was depleted, or insufficient for most agriculture, a more plentiful source of fertilizer nitrogen was needed.

Now, fixed nitrogen comes from nitrogen gas.  A highly energy-intensive process is used to convert nitrogen gas into fixed nitrogen.  The Haber process converts gaseous nitrogen into ammonia, which is used for fertilizer.  From wikipedia, "Fertilizer generated from ammonia produced by the Haber process is estimated to be responsible for sustaining one-third of the Earth's population.It is estimated that half of the protein within human beings is made of nitrogen that was originally fixed by this process."

Further quoting from the linked wikipedia article, "The Haber process now produces 500 million short tons...of nitrogen fertilizer per year, mostly in the form of anhydrous ammonia, Ammonium nitrate, and urea... 3–5% of the world's natural gas production is consumed in the Haber process (~1–2% of the world's annual energy supply). In combination with pesticides, these fertilizers have quadrupled the productivity of agricultural land....nearly 80% of the nitrogen found in human tissues originated from the Haber-Bosch process Since nitrogen use efficiency is typically less than 50%... our heavy use of industrial nitrogen fixation is severely disruptive to our biological habitat.

Then what happens?  Unless people are growing muscle (children), virtually of of the consumed food nitrogen is converted into urine.  Even in agricultural animals, most is made into urine, and much less into meat and dairy protein. 20% of dietary nitrogen consumed by dairy cows is converted to milk and meat.  The rest is excreted.   What happens to human urine nitrogen?  It is diluted by large amounts of purified, drinkable water - gallons to flush a cup or two of urine - which then goes into sewage treatment plants, and much ultimately into rivers and the ocean.  Where the nitrogen fertilizes harmful algae and causes significant damage to the ecosystem.

Organic growers have other sources of nitrogen.  There is blood meal, fish emulsion, alfalfa meal, composted plant material, especially grass, barn bedding - containing animal urine and feces, and other sources.  If not grown on site, all are purchased.  Blood meal, which comes from slaughtered animals, is expensive.  Animal wastes can be useful, especially if the animals are grown in one's own yard, such as chickens.  Alfalfa meal usually needs to be purchased, but at least can be grown with the alfalfa's symbiotic bacterial fixing nitrogen, instead of via the Haber process.

There is also human-sourced urine.  Since almost all f), ood nitrogen that goes in, must go out, urine contains most of the dietary nitrogen.  70% of nutrients excreted by humans are in the urine.  The chemical form is readily available to soil bacteria and thus to plants, same as Haber-process ammonia products.  In theory, if all of an individual's urine went into the agricultural production of plant protein, then much of an individual's protein requirement could be via recycled nitrogen.  Urine NPK (see below, roughly 11:1:3) is comparable in nitrogen content to fish emulsion (5-1-1 or 5-2-2 but my jug states 12:0:0), or blood meal (13:0:0 or 12:1:1),

What are the challenges that prevent use of urine in horticulture and agriculture.  In the case of this blog, horticulture?  Social and personal aversion, in-grained behaviors, established infrastructure for the current system, lack of established infrastructure for nitrogen recycling, ignorance, public health concerns, convenience issues, misuse, and esthetics come to mind.

Aversion - I suspect aversion comes from protective biological mechanisms, and cultural factors.  Aversion might protect us from unsafe or toxic substances.  It should be no more objectionable to use urea nitrogen from Homo sapiens, than ground up rotted fish parts (fish emulsion), rotted animal feces (composted manures), fermented animal urine (bedding compost), and steamed, dried blood from slaughterhouses - blood meal.  Chemically derived nitrogen fertilizer, in concentrated form, is highly toxic, or explosive.  So even though not from living or dead animals, is not less objectionable.

Ingrained behaviors - on a societal level, it's true.  Converting a city's urine to agricultural use would be daunting.  On a horticultural level, for one's own garden or homestead, especially males, there is nothing easier than urinating into a plastic one-gallon jug.  It's simpler than using the toilet, which has added movements on raising and lowering the seat, and flushing.  Among people who promote use of urine, there are options for women as well.

Established infrastructure - again, agricultural scale, daunting.  Individual scale, a gallon milk or juice jug is free, and would otherwise go into trash or recycle.  Then  use in garden via pouring into watering can, already there, and diluting with water from hose, already there.

Ignorance - the internet is great for autodidact learning.  Maybe the biggest hurdle is the weirdness stigma, or aversion factors, or esthetics.  In addition, there are few reliable sources that say how much, how much to dilute, when to use, over what area, under what circumstances.  Sources disagree with one another, substantially.  As I mentioned earlier, many internet discussions on the topic (such as on gardenweb) are filled with opinions, not data.

Public Health Concerns - Human urine should be no more concerning than use of animal urines.   Studies have repeatedly demonstrated safety of human - derived urine.  Those studies have been in 1st world and 3rd world countries, using community sources.  For the individual gardener, it's even less of an issue.  Sources repeatedly point out that urine from a healthy person is sterile.  Bacteria start growing in the urine when stored.  It can be used fresh, or stored long enough that the self-fermentation sterilizes the urine via ammonia production from urea.  Fresh use is more appealing, because significant nitrogen may be lost in storage via ammonia gas, and because fresh use does not involve storing jugs or urine.  Fresh urine has much less odor, compared to stored urine.  Again, the esthetics issue.  Most authors state, people with urinary tract infections shouldn't use their urine for horticulture.  I don't know if that precaution is necessary.  But it might be due diligence.  Outside of disease concerns, there are concerns regarding medications, antibiotics, metals, and chemicals in the urine.  There too, human urine is considered cleaner than animal sources, which use antibiotics approved, and not approved, for human use, for growth promotion and disseases; which create and spread antibiotic resistant and disease causing bacteria.  Animals are also treated with hormones, that may go into the urine in larger amounts than seen for humans.  I'm speculating there.

Convenience - For the home gardener, the convenience issue is mainly, there may be need for nitrogen supplement when there isn't enough, and urine production is continuous even when the garden is not growing.  Strategies include storage in containers, use on compost when not needed in garden, in-soil storage (basically, pour onto fallow ground.  Not well researched.  Nitrogen losses may be significant and salt accumulation may occur).  I could see this being a challenge.  As I noted, using fresh product seems preferable to older product.

Misuse - ties into ignorance.   Use too much, at the wrong time, and there could be leaf overgrowth as with any nitrogen fertilizer.  There could be accumulation of salts, especially in arid soils. Use concentrated, and salts may be toxic to plants, as noted in places where dogs urinate on grass.  Use, without watering into the soil, and there could be odor production.

Esthetics. - Mostly that's the odor issue.  I know there is urine odor in the dog yard in the summer.  When I am diligent about watering that grass, there is no odor.  And the grass growth is very lush and green.  So is the tree, which has flourished for 14 years.  The urea and other compounds wash into the soil, where bacterial ecosystem converts them into living cells, and into products that are bound by soil vs. taken up into plant roots, and used for growth.  Diluted, or used and watered - in, there should not be an odor issue.  Then again, fish emulsion, animal manures, barnyard waste, all have plenty of odor, which dissipates as does the urine odor.

 From Akvopedia, "
"Ecosan is not so much a technology as a way of thinking. It views (treated) human excreta and greywater as valuable resources that can be put to productive use. In that sense, it requires a change of thinking about waste issues in terms of recycling and closing material loops, where waste is no longer regarded as waste but as a resource."   In that case, I would call it a product, rather than waste.  But that's just me.

 I think this discussion puts together most objections related to nitrogen recycling via capturing what is lost from urine disposal, and instead rerouting this resource into gardening.  The next challenge is, how to use urine as a horticultural resource, in the garden or homestead, or other permaculture setting.

In this discussion, I won't get into how to collect or store urine.  The easiest approach is to urinate into a gallon jug and use within a day or two, to avoid spoilage.  There may be nuances involving season, weather conditions, or what is growing, when.  In addition, no one needs to let "the perfect" be the enemy of the "good enough".  If not needed or not able to save at all times, it can be flushed as is normally done by virtually everyone, virtually all of the time.

I have not sorted out all of the concerns about dilution, application, etc.  Most web info lacks many details.   It seems like most is just opinion.  The NPK for urine varies based on diet and nutrition, and water intake, but is roughly 10:1:4This source, states the urine of the average Westerner is 11:1:2.5.    Close enough.

From a different source (University of Hohenheim), one liter of urine contains:

Nitrogen 7 grams
Phosphorus 1 gram
Potassium 2 gram
Sulfur 1 gram
Magnesium 80 mg
Calcium 200 mg 

That data reflects the diet of the people studied.  These numbers are highly variable across cultures.  And, I imagine, individuals.  Then again, this is not rocket science or brain surgery.  This last reference - Stockholm Environmental Institute -  states urine nitrogen content is 3 to 7 grams per liter, and gives some rules of thumb for urine utilization - "general rule of thumb is to apply the urine produced by one person during one day (24 hours) to one square metre of land per growing season (crop). The urine from one person will thus be enough to fertilize 300-400 square meters of crop per year and even up to 600 square meters , if dosed to replace the phosphorus removed by the crop."  So for an 8X4 raised bed, that could mean dilute 1 quart of 1 liter of urine to about 2 gallons in a watering can, sprinkle that over the entire bed early in the growing season, then repeat a month later.  In an orchard, or around shade trees, it could mean applying a similar amount over a similar area, after frost ends and again a few weeks later.  For plants that grow throughout the winter, an application during winter might be helpful.

SEI also states, "Urine is a high quality, low-cost alternative to commercial fertilizers. It is especially rich in nitrogen and also contains substantial amounts of phosphorus and potassium. The fertilizing effect is rapid and the nutrients are best utilized if the urine is applied prior to sowing and up until two-thirds of the period between sowing and harvest."

The Hohenheim source states, urine does not need dilution when applied directly to soil, but is best applied before light rain The rain then washes the urine washes into the soil.  It is speculated that a heavy rain would wash the urine deeper than roots grow.  I don't know if that's true.  Many roots can grow several feet deep.  They also add, this is the same for other nitrogen fertilizers, not just urine.  Different sources give different opinions.

This reference states that using urine fertilizer every other week for 2 months, in Uganda, was seen to double vegetable yields.   That compares to no fertilizer, and the soil quality may have been poor. 

This reference discussed use of urine in Finland, for cabbages that went into sauerkraut.   The effect was essentially equal to using chemical fertilizers.  Sauerkraut is fermented from unwashed leaves, but there was apparently no issue.  This study showed that urine, used with wood ashes, resulted in 4-fold increase yield of tomatoes.  Again, in similar range to benefits of chemical fertilizers.  Also, the initial soil was nutritionally poor.  This article discussed use of human urine for fertilizer in Nepal. There are discussions of urine as fertilizer in China and Africa.

Assuming that one has decided there are benefits for urine / eco-san as fertilizer, and the negatives are addressed, then where to go from there?  There is so much conflicting info, it's hard to know.  Some thoughts....

#If possible, use fresh.  If out of season, urine can be stored in plastic 1-gallon jugs.  Some authors contradict this, and prefer stored urine.

#Dilute.   The mid range of most articles is 1:5.  Close to that, using approx 1/3 gallon in a 2-gallon watering can, makes it 1:6.  Some references call for far greater dilutions, 1:10 or more.  This is especially for seedlings or indoor plants.  I have not found evidence-based analysis of that recommendation.  Probably better to use to little, than too much.

#Water it into the soil.  I think when diluted 1:6, there isn't much need to water it in.  During non-rainy seasons, a light watering might be enough.  If there is odor, water it more.  Some authors make trenches or holes, pour in the urine, then cover them again.  That sounds like too much work, especially for trees and grass.

#Use urine for nitrogen-demanding plants.  That's leafy vegetables, tomatoes, okra, onions, garlic, corn.  Do not use for plants that are damaged by too much nitrogen, such as root vegetables.  Pour it on the ground, not on the leaves.

#Use urine when crops are actively growing.  For most crops, when they are setting fruits/vegetables/seeds, they don't take up nitrogen, so it's wasteful to use it at that time.  Used in late summer or fall, high nitrogen results in weak frost-susceptible growth on trees and shrubs, so it makes sense to stop by mid summer.   I've tried reading up on winter fertilizing.  Some references recommend application of fertilizers for trees and shrubs during the winter, to be available when growth starts.  I don't know if that is beneficial, or wasted, or stimulates growth that might succumb to late frost.   For plants that are especially susceptible to a late frost, it might be best to wait until after the last expected frost date.  Another option, apply to grass during cool season, then mow the grass for compost or mulch.  In my area, grass is growing lush and green now, even though it's January.

#If not able to use the urine, that's when flushing makes more sense.  Or adding it to a compost bin.  The high nitrogen content would speed composting of leaves or straw, newspaper and cardboard.

That's a lot of discussion for what seems like a simple topic.  But I think it's worth a serious thought, and sorting out the wheat from the chaff.  Much more work is needed to discover the best uses, how, how much, when, where, for what.

Resources:  Above links, plus
Scientific American.  Urine is an effective fertilizer.
Mercola.  Human urine is shown to be an effective agricultural fertilizer.
NW Edible life.  How to use pee in your garden.
Gizmodo.  Is human pee the future of fertilizer?
Permaculture Research Institute.  Urine.  Closing the NPK loop.
BigBlogOfGardening.  Human urine as fertilizer in your home garden?
EcoSanRes.  Guidelines for the use of ...
Permaculture in New Zealand.  It's as good as commercial fertilizers with no hygeinic issues.

Unless otherwise noted, source for all illustrations was


  1. Brilliant! That's thinking outside the box! Definitely going to try it!! I knew there was a good reason for calling it the RECLAMATION FACILITY!!

  2. Shaz Oz, the more I read about this, the more sense it makes.

    During the winter I applied "liquid gold", diluted about 1:4 or 1:6, around most of the new shade trees. I don't know what the trees will do yet, but the grass around those trees clearly grows much faster and greener, compared to the rest of the lawn. So far so good. I hope it will give the trees a boost this year.