"Problems of over-fertilization are common in developing countries, where the farmer relies upon N input to obtain maximum crop yield. Excessive application of N increases the residual NO3-N in soil and produces favourable conditions for leaching below the root zone."

from this book: books.google.co.uk/books?id=ONYZm_J0gr8C...#v=onepage&q&f=false

" The water and nutrient holding capacity of clay soils is higher than that of sandy and silty soils, therefore leaching of NO3, P, other nutrients and organo-chlorines is dependent on soil texture. Conversely the risk of accumulation of harmful components in the root zone following repeated application of large doses of manure is higher in heavier textured soils than in light soils. Clay soils become more easily waterlogged after heavy rainfall because of a lower hydraulic conductivity, i.e. the possible rate of water transport through the soil. Under waterlogged conditions, denitrification can occur and harmful N2O may be formed. Under extreme acid or alkaline conditions (pH<4 or>9), soils tend to deflocculate, the structure is destroyed and leaching of many organic and inorganic components becomes inevitable. Volatilization of NH3 from soils with higher pH values is greater than from those with lower pH values."

From this FAO document: www.fao.org/wairdocs/lead/x6113e/x6113e05.htm

"Toilet compost (TC) and human urine are among natural fertilizers, which raise interest due to their double advantages to combine sanitation and nutrient recovery. However, combination of urine and TC is not so spread probably because the best ratio (urine/TC) is still an issue and urine effect on soil chemical properties remains poorly documented. This study aims to determine the best ratio of urine and TC in okra cultivation, by targeting higher fertilization effect combined with lower impact on soil chemical properties. Based on Nitrogen requirement of okra, seven treatments were compared: (T0) no fertilizer, (T1) chemical fertilizer (NPK: 14-23-14), (T2) 100% urine, (T3) 100% TC, (T4) ratio of 75% urine + 25% TC, (T5) 50% urine + 50% TC and (T6) 25% urine + 75% TC. Results indicated that T4 (75% urine + 25% TC) gave the highest plant height and yield. In contrast, T2 (100% urine) gave the lowest results among all treatments, indicating toxicity effects on plant growth and associated final yield. Such toxicity is confirmed by soil chemical properties at T2 with soil acidification and significant increase in soil salinity. In contrast, application of urine together with TC mitigates soil acidification and salinity, highlighting the efficiency of urine and TC combination on soil chemical properties. However, further investigation is necessary to refine better urine/TC ratio for okra production."

from this research paper www.tandfonline.com/doi/abs/10.1080/09593330.2014.984774

Urine application has a different effect on different soils in different places. This is just a fact, not "over thinking".

Dear Joe,

In response to this comment:

Yes, I know that some here have had good results with their urine irrigation schemes, but these must be unusual situations and should not be seen to apply to everyone else in all situations. That's clearly not the case, otherwise there would be no need to have agronomists and soil scientists advising farmers on the correct amounts of fertilizer to use on their crops.

Urine fertilization has to a large extend happened in a developing world setting. The problem you describe of soils with N (or P) levels that are already so high that additional nutrients do not help plant growth does -in my experience- not apply in those cases. The nutrient saturated soil problem is one associated with intensive livestock keeping. Where so much dung is spread on the land that it is over fertilized. This is probably why most trials with urine fertilization have worked well.

In general I think your comments on urine fertilization in this thread are valid. However, I think, you are "over thinking" things for practical purposes in the developing world.

Best

Marijn

Dear Joe and others,

Regarding biochar from sanitation, this does happen (at close to full scale pilots), see for example:

forum.susana.org/forum/categories/224-th...nitation-and-hygiene

As I understand bsoutherland's post, he is not pyrolyzing the fecal sludge from the toilet, but crop residues. The biochar from this is then used as a sort of "nutrient sponge" for the urine collected in a diversion toilet.

Regards

Marijn

bsoutherland, that's interesting, I've often wondered if anyone was attempting biocharring as a form of sanitation.

There are various designs for "rocket" stoves which char wood. In brief, rocket stoves are lit in a pipe which is embedded in an cabinet full of insulated material to ensure an efficient burn. If the insulation material is replaced with wood and holes are provided to allow gases to be released (which are then burned), the wood is charred.

en.wikipedia.org/wiki/Rocket_stove

If instead the insulation chamber was a collection vessel from a latrine, it ought to be possible to char faecal waste.

There may well be issues with the wetness of the material, smoke and gases - have you been able to overcome these, bsoutherland?

To make biochar, I use a horizontal retort barrel with an insulated lid resting within a larger horizontal barrel with ashes between for insulation. The retort is fired via a horizontal flue pipe that passes from the outside through the inner retort running along the bottom then bending 90 degrees to exit vertically near the insulated lid. A start up fire is built inside the horizontal flue. This internal flue pipe has a series of small holes allowing pyrolysis gasses to enter, burn and sustain the reaction until all volatiles are burned off leaving pure charcoal.
While the start up fire is burning inside of the flue, moisture from the heated biomass is vented from the retort through a small pipe. When the moisture is exhausted and volatile gases begin to exit the small pipe, it is capped. Thereafter all volatile pyrolysis gases are forced through the series of small holes into the internal flue where they ignite to intensely heat and pyrolyze the biomass charge.

"The wait time for reuse has now gone from months to minutes."
Can You post some more information about your biochar methods?
Harry
Tasmania

This discussion is very helpful. For the sake of expanding possible approaches to the use of human excreta to improve agricultural outputs consider a charcoal (biochar) based system. Use charcoal for odor control and splash control in a simple two bucket urine diversion toilet. Pyrolyze crop waste in a retort to produce the charcoal. Use the excess heat released from the retort to heat the feces bucket to kill pathogens. (An alternative method uses a TLUD cook stove to heat the feces bucket. TLUDs are clean running biomass cook stoves producing charcoal as a byproduct.) This system creates an inoculated biochar rich in nutrients and organics. The wait time for reuse has now gone from months to minutes. (If one insists on vermicomposting, worms like biochar in their diet.) I am currently testing this system in a village setting to see if it can become a sustainable business. Since the metal feces buckets are covered and heated BEFORE dumping, potential for pathogen exposure is greatly diminished. We have also devised a simple wide plastic clip that securely holds buckets together, eliminate messes, and allows the use of a standard enlongated toilet seat. A frame of a few inches height sitting on top of the buckets creates enough height to provide clearance for scrotums. Our customers love this. It sure beats the fly infested cesspool outback.

One of the advantages of human effluent is that our diet comes from a range of sources. This is in contrast with, for example grazing animals. Their waste has the same nutrient deficiencies as the land they are grazing, while we eat food that comes from all over the world, so our waste tends to have a good balance of nutrients. Without getting too distracted on soil science (one of my favourite subjects ), I want to produce nutrient-rich and NPK-balanced effluent, in contrast to municipal treatment where the treated effluent ends up in a water body, so they try and minimise the nutrients being discharged. To avoid loss of N into the air the effluent needs to go into the soil as soon as possible. Seems easy to me.... but I can afford a pump and dripper lines... and I like growing things.

cheers
Dean

goeco wrote: Fact is that urine is not a balanced fertiliser. What I am trying to raise is that vermicomposting adds nutrients to the liquid effluent. By drying feces, UDDT systems make "active" biomass (a good carbon and nutrient source once decomposed), plus urine. There is a disconnect because urine is not a balanced fertiliser. In contrast, vermicomposting digesters should produce a NPK-balanced nutrient-rich effluent. The issue I have is that this has apparently not yet been quantified by published research.

What I am trying to explain is that a vermicomposting digester produces "stabilised" humus (a good soil amendment rich in carbon) that apparently has low levels of pathogens (again not quantified) and the bulk of fecal material is reduced to liquid which combines with urine to be a nutrient-balanced liquid fertiliser (with variable pathogen levels depending on what happens next). There are two options for the liquid, secondary treatment and surface drippers, or simply discharging directly to underground soakage trenches that feed suitable food crops like bananas that respond to water + balanced nutrients.

Mmm. This relates to another term we should be using when discussing amending things to soils - the idea of "nutrient availability". It is complicated chemistry, but basically it means that there are different forms of NPK, some of which can be taken up by the plants and some of which cannot. Part of the problem with urine is that urea is immediately available, so if the crop is not actually needing the nitrogen right now, it can easily be lost altogether from the soil. So composting (and also processes like vermicomposting) help by changing the availability of the nutrients. It sounds counter-intuitive, but these actually sometimes make the nutrients less available, so more of them are stored in the soil rather than being lost as I described above. So a farmer might find that the compost does not have a rapid effect on this season's crop as you might see with a bag of fertiliser, but there is a long term improvement in the fertility of the soil so in the long term the crop growth is improved.

So this is the difference between a mix of fresh urine and faeces and a compost (or vermicompost) - the material has been "stabilised". The organisms have also changed the physical structure of the material to make it more suitable for use in the soil.

Even if the balance of NPK in the urine is exactly what is needed by the crop, a lot of the nitrogen will be lost during storage and application, and if it isn't applied at exactly the right moment may have little effect on the crop growth. Of course this depends again on exactly what the situation is.

In contrast the nutrients in the compost have been stabilised, so there are fewer losses during application and the timing is less critical because of the long-term release of the nutrients.

By recycling balanced nutrients to crops, the risk of growth-limiting factors (especially lack of P) is reduced. One thing that needs to be clear is that by increasing productivity of land using liquid only ('booster'), organic matter (biomass or 'soil amender') levels are increased and so improve soil quality by being returned to the soil. Production of biomass is mostly limited by two factors, availability of water, and nutrient shortage. Abundance of some nutrients and shortage of others is no better than shortage of all nutrients.

cheers
Dean

That's correct, although we should be careful in suggesting that compost will solve all nutrient deficiencies in crops and the soil. Again, without knowing what those deficiencies are, we'd be operating in the dark. That said, because the nutrient availability in the stabilised compost/vermicompost has been changed, there is likely to be less of a problem with excess nutrients in the soil from compost than you'd get with an oversupply of urine or a commercial fertiliser. It's very difficult to add too much compost!

On the pathogen point, the best research I've seen suggests that worms alone not able to reduce pathogens to safe levels, in contrast to composting where the high temperatures kill them off.

muench wrote:
Urine is a complete fertiliser and rich in P. In fact, it is usually valued especially for the P content (as well as the K and the micronutrients; more so than for the N). Also when compared to a commercial liquid fertiliser, don't forget that those cost money whereas urine is in theory for free (although yes, you may have to transport it which incurs costs as it's more diluted than commercial fertiliser).

I'm sorry but this is quite wrong and misleading, Elizabeth.

Plants require the correct amounts of various macronutrients (that's the NPK that we're discussing above) as well as a range of micronutrients to grow properly. Mostly they get these supplied to them from the soil. When the soil does not have enough of one or more of the nutrients, the plants will not grow very well.

Urine is a good source of urea, which is a good source of nitrogen. However, it is in no sense a "complete" fertiliser as it does not have equivalent levels of P and K, never mind the micronutrients.

But even if it did that's irrelevant as different plants in different soils need different amounts of NPK. In some situations the soil already has high levels of N, so adding more in urine is going to make no difference at all.

This idea that one can add anything to a farmed field and this will magically be what the soil and plant need is quite wrong.

Yes, I know that some here have had good results with their urine irrigation schemes, but these must be unusual situations and should not be seen to apply to everyone else in all situations. That's clearly not the case, otherwise there would be no need to have agronomists and soil scientists advising farmers on the correct amounts of fertiliser to use on their crops.

I agree with Dean that applying faeces will help in several respects, both in terms of adding other macronutrients and with adding organic matter to the soil. But even here the overall amounts of NPK may still not be what is needed by the crop and still may not be enough to replace all fertilisers - it entirely depends on the soil and the crop.

This whole subject is extremely complicated and site specific!

Than main factors that influence nutrient levels in urine are:

1. Levels of protein in the diet (doesn't matter whether vegetable or meat). A high protein diet results in high levels of N.
2. Amount of water consumed by the individual. This affects dilution of nutrients in the urine (absolute levels), but does not affect the balance of nutrients (relative levels).

Fact is that urine is not a balanced fertiliser. What I am trying to raise is that vermicomposting adds nutrients to the liquid effluent. By drying feces, UDDT systems make "active" biomass (a good carbon and nutrient source once decomposed), plus urine. There is a disconnect because urine is not a balanced fertiliser. In contrast, vermicomposting digesters should produce a NPK-balanced nutrient-rich effluent. The issue I have is that this has apparently not yet been quantified by published research.

What I am trying to explain is that a vermicomposting digester produces "stabilised" humus (a good soil amendment rich in carbon) that apparently has low levels of pathogens (again not quantified) and the bulk of fecal material is reduced to liquid which combines with urine to be a nutrient-balanced liquid fertiliser (with variable pathogen levels depending on what happens next). There are two options for the liquid, secondary treatment and surface drippers, or simply discharging directly to underground soakage trenches that feed suitable food crops like bananas that respond to water + balanced nutrients.

By recycling balanced nutrients to crops, the risk of growth-limiting factors (especially lack of P) is reduced. One thing that needs to be clear is that by increasing productivity of land using liquid only ('booster'), organic matter (biomass or 'soil amender') levels are increased and so improve soil quality by being returned to the soil. Production of biomass is mostly limited by two factors, availability of water, and nutrient shortage. Abundance of some nutrients and shortage of others is no better than shortage of all nutrients.

cheers
Dean

The N-P-K values in urine can vary greatly depending on the diet. as an example the nutrient value for vegetarians is higher than meat eaters. The caloric intake will vary the nutrients in urine and the more water you drink the more you dilute the urine. The deeper the yellow, more nutrients. The average person will urinate about 1.2 kg of urine per year. In that urine will be 3.5kg N, .4 kg P, and 1 kg K. Different studies show different amounts so I am sure there will be different numbers posted.
The urine will have only minor affect on micro nutrients. Healthy micro nutrients comes from healthy soil. This is achieved by using the human fertilizer tilled into the soil. Commercial fertilizers kill the micro nutrients. Thought the feces is not as rich in nutrients it does contain about 10% of the N and K as well as 50% of the P. The feces (human fertilizer) also acts as a soil conditioner resulting in high humus, works, moisture retention, and micro organisms that produce micro-nutrients.
A person produces almost as much human fertilizer as is required to grow the food that will sustain him. This is one of the reasons that I am so positive on the UDDT.