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

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.

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

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.

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?

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

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

"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".