Hello All, Thanks for the comments and suggestions around Treebogs and their use in humanitarian scenarios.  As the originator of the term 'Treebog' and having used a Treebog for over 3 decades, I attach some information which I hope will inform and allay fears, as well as further the discussion. Blessings,  Jay

Hi everyone, 

Great thread. 

I have been implementing large-scale humanure composting projects for 12 years. We do not separate or divert urine, however we do only work in contexts where there is sufficient available carbon material to use as cover material and for the composting process. We use local sawdust, rice hulls, and cut grasses for the composting procedures. In contexts where we have not had enough space or carbon material to compost correctly, we have implemented Fosa Alterna toilets, and hybrid trench sanitation approaches. I do believe that trench sanitation needs more exploration in high-density camp contexts, as well as on-site composting. 

Can you please explain the science behind your statement:

 "Without the moisture from the urine the feces will dry quickly and have minimum odor.  When pathogens die the feces it can be used as a soil conditioner."

How do harmful pathogens just die?

Without treatment, these approaches may provide a better user-interface at the toilet experience, but overall, I do not believe they provide solutions that are scaleable. Pathogens in feces simply do not die without thermophilic composting. Therefore, overtime, this system will probably result in both soil and water pollution. I also take issue with comments here that continue to overstate the "health risks" involved with processing excreta. Skills training can reduce these risks completely, and we've trained dozens of humanure compost technicians with zero incidence of infection or illness associated with composting, even during the cholera pandemic in Haiti. 

According to the United States Composting Council the definition of composting is defined as:

Compost - is the product manufactured through the controlled aerobic, biological decomposition of biodegradable materials. The product has undergone mesophilic and thermophilic temperatures, which significantly reduces the viability of pathogens and weed seeds (in accordance with EPA 40 CFR 503 standards) and stabilizes the carbon such that it is beneficial to plant growth. Compost is typically used as a soil amendment, but may also contribute plant nutrients. (AAPFCO definition, official 2018)  Finished compost is typically screened to reduce its particle size, to improve soil incorporation. 

Feces don't just compost themselves. Decomposition and dehydration occur, however these natural processes do not reduce pathogens to acceptable levels defined by either the WHO or United States EPA. 

I would love to visit this pilot next time I'm in Kenya. 

Sanitation experts in developing countries are always looking for easier/cheaper systems to build but all have limitations.

1.  If you mix urine with feces you will have more odors. The ammonia in the urine mixing with the feces will make the system unpleasant at the least.  This will be especially acute since there is no vent.
2. Since the urine and feces are expected to be absorbed by the ground that will only work as long as the moisture does not exceed the ability of the soil to absorb.  If you produce more than the soil can absorb then the ground around the toilet will get moist and attract rodents as well exposing the pathogens to humans.
3. Most of the nutrients are in the urine which is also very low in pathogens so if you separate from the feces it can be used quickly.  Without the moisture from the urine the feces will dry quickly and have minimum odor.  When pathogens die the feces it can be used as a soil conditioner.
4. With the tree bog you must plant all trees close so the roots can absorb the nutrients.  If you could take the nutrients to the plants you have a much greater range where you could plant the trees.
5. In many developing countries the drinking water is gotten close to the surface so there is a much greater chance of contamination with the drinking water.

I have engaged with Jay, the proponent/creator of the system. I think the concept of using the resource in situ has a wonderful elegance to it, which also much reduces FSM/compost handling, so associated health risks. As a humanitarian WASH person working in many, many camps in many contexts, all of the things you raised I have raised with Jay. You may find this article of interest; www.re-alliance.org/post/looking-for-a-s...on-that-will-w-a-s-h

I camped at a place in Wales last year where a single chamber treebog was built and indeed heard about its limitations there, on a what admittedly was a very sub optimal site.

My conviction is that we should face, understand and design/build to address these limitations and get the system optimised because its so important. To this end I have in the last weeks designed an adapted treebog and run a compost toilet training course at Black Mountains College (Wales) where I work. It will be some months before we start to use and years before we gather much data. Modifications made;
UD
Twin pit (sized for 3 years as per traditional compost toilet sludge/compost accumulation rate estimates)
Pallet sides with chicken mesh for rodents, rather than just chicken mesh
Surface water run off skirt
If we face smell /visual problems we will add vent pipe and adopt other measures.

Jay acknowledged the lack of data on how fast vaults/chambers fill. This data is much needed. 

However my bottom line is lets test and stretch this system, while knowing and stating its limitation and use this widely.

I can see possible downstream problems with urine and solids mixed creating a health risk. Could the design of the pan be changed to embody Urine diversion for either collection/ use or separately irrigated ? Washing water would continue as originally planned.
Otherwise this is a good design.
Ross

Hi Aaron,
Agreed on all points. Ventilation, fly and rodent protection are design issues that could be easily overcome.

However, although the concept itself is good: "enables the faeces and urine to be deposited on the soil surface, underneath the platform, where the solids are composted into soil"...
...my greatest concern is with the idea that "the liquid soaks into the earth below, feeding the root zone of the planted species surrounding the Treebog", because although in practice this would work for small numbers of users, I would expect communal toilets with handwashing and anal washing to generate more liquid waste than the clearly small soil area's capacity to absorb. Therefore the surplus liquid would have to drain somewhere else. This could be addressed by expanding soakage areas e.g. using plastic pallets covered by textile cloth which is covered with soil.

I'd also be worried about fecal sludge accumulating faster than it breaks down. If there is no handwashing/anal water being added the urine concentration will generate foul smells and slow down the decomposition process. Added water is essential, but then requires more soakage area. 

If the soil surface area is insufficient for the sludge to spread unhindered, decomposition will slow. This is because soil surface area in contact with the waste directly affects rate of decomposition.

These simple systems only work until there is more waste than the system can cope with... the key might be understanding its limitations. Generally those who enthusiastically sing its praises won't have done the quantitative research.

cheers
Dean

HI all

I have been approached by a permaculture centred NGO about Treebogs I am wondering if any of you have any experience with
them? The people I am speaking to want to apply it to the Kakuma Refugee camp in Kenya. They have one year of positive experience with them in the camp already. On first observation of the design, I have some reservations. But I don't want to be over-critical and over judgemental of the technology of others who have already had positive experiences.

I have the following reservations:
1. Co composting of faecal matter will create large volumes to break down (Tree bogs are not always a two-chamber
approach and so, it is likely that mass accumulation of faecal sludge is greater than the chamber volume, especially in IDP CAmps where the
user numbers may be quite high)
2. Unclear ventilation and air circulation (No chimney to aid ventilation)
3. Unclear fly protection
4. Faecal matter and urine are not on a platform and are not that well protected from overland flow during heavy rains. I am concerned that saturated earth and sloping overland flow could take black waters out of the chamber and into the community.
5. The raised platform prevents disabled and elderly from easy access

Advantages are - 
Clearly, the nutrient recovery and recycling in a Treebog is going much quicker and anecdotal evidence in the projects that these people have done suggests this is true (Mangos fruiting in 18 months). It stands to reason feeding plants well has positive results as does breakdown with higher levels of aerobic activity as in a pit. Also, the saturation of the topsoil as the faecal matter and NPK high urine will be closer to the roots (of young saplings) if sludge is stored closer to the surface of the soil and so more readily available to the roots.  The addition of anal and hand wash waters will feed trees as well. 

While (to my mind) the design seems to pay not enough regard to pathogen removal/containment or seperation. The advocates claims this activity is transferred to the trees and Microrizal network and accompanying organisms etc. 

I feel like correct sizing, (a double vault)  the addition of a surface water barrier and Sato pan might be sufficient to feel sufficient isolation of faecal matter is happening>... thoughts and reflections, please

Best wishes Aaron

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