Hi Stew,

Recycling of cover material is imminently practical, as no solids need to be transported long distance, to or fro, with who knows what vehicle and who knows what petroleum (or donkey power). It also inoculates the new feces with at least some of the same soil microbes that broke down the feces of the previous cycle. If we have reliable treatment (via heat, sun, thermophilic composting and/or long storage), no significant amounts of pathogenic microbes will remain and there is minimal health risk. Remember that any system can be used incorrectly (like having flush toilets dump straight into rivers where people swim and drink).

In my experience, recycled cover material controls smell and flies much better than the mix of sawdust and ashes that we used before. I am also convinced that this gets even better year after year, likely due to accumulation and natural selection of the soil microbe species present and potentially even some evolution, given that microbes evolve so quickly. See the scientific papers cited in this interview, for support for the idea that finished compost is one of the best materials for covering the smell of composting or landfills:
www.chekhovskalashnikov.com/human-waste-disposal/

The limitations to this recycling are mental and cultural, due to fecophobia (irrational fear of feces) and the illogical belief that "once feces, always feces" (and that the entire planet is gradually being converted to feces), since no one would identify its origin by smell, color or texture. In addition, it mostly consists of the original cover material, since the feces largely disintegrate, with their water evaporating out and their microbes killing each other until they occupy very little volume.

If users are concerned about pathogens still persisting, they will remember to wash their hands, which they currently often do not. The recycled cover material can also be added mechanically, avoiding direct contact with the user.

Yes, one can check "finished biosolids" for Ascaris Helminth eggs by looking at them with a microscope and these eggs are quite characteristic, with their golden color and bumpy surface. There are techniques to concentrate the eggs and increase one's chances of finding them, which is the subject of another current thread:
forum.susana.org/forum/categories/26-hea...ce-a-better-way#8176

Last year, a student intern did one, isolated 3M PetriFilm trial for E. coli in the one-year-old recycled cover material by mixing it into water and applying the normal procedure for water samples. During incubation, 2 blue spots developed, indicating that 2 E. coli bacteria were present -- roughly an order of magnitude acceptable for a swimming pool. (I can look up more detail on this trial, if anyone likes.)

Update. I no longer mix wood ashes into the recycled cover material, since I do not want to kill the beneficial microbes. Also, most people do not have access to large amounts of ash ... which might best be used as fertilizer (including mixed with urine). I do mix in some 10% rice hulls, to replace lost volume through decomposition of the sawdust originally used as cover material and to increase air flow through the pile. (Other resistant, bulky, food-processing wastes, such as crushed egg shells, squash shells or manioc fibers, could also be excellent to mix into cover material.) I also sometimes replace lost volume with dry organic soil, in order to maintain a one-year detention time (longer than probably necessary, for peace of mind and further drying).

There is more detail on this recycling in previous posts:
forum.susana.org/forum/categories/17-fer...rt-of-processing#505

forum.susana.org/forum/categories/17-fer...imit=12&start=12#531

Thanks for asking, Stew. Keep sending any questions you may have.

Best wishes,
Chris Canaday

Hi Chris,

No, not involved in that India project. One Rotary WaSH project in India, more often in Indonesia and CenAm, one is percolating in Tanzania.

I've followed some of your posts here, viewed website and video ... very informative!

Idea of wax or sealant on bamboo is interesting; might extend life 6-12+ months. The villagers came up with the idea of gedek on bamboo frames; but gedek (aka kedek) is like dried palm fronds, will rot too quickly. We are now looking for the woven plastic bags. No PET beverage bottles in Sumba villages; quite primitive rural area, as much or more so than sub-Sahara.

I see you use dried humus (re-purpose) to be the drying carbonaceous material for next round of feces; how does that work? As well as firepit ash, sawdust, minced leaves?

I read lots on 6-12+ months for dehydration, some speculation on shorter periods ... but being a biologist, how does one really test to verify helminth egg inactivation? Looking a samples under microscope doesn't tell, does it?
And have you used 3M Petrifilm on a suspension made from the material to count e.coli or coliform CFU's?

Stew

Dear Stewart,

Thanks for the update. Is the Rotary also involved in Lucas's project in India? Please tell us more about yourself and the advances of the project.

Woven, polypropylene sacks are usually very easy to get, as they are commonly used for rice, flour, sugar, chemical fertilizers, etc. Used sacks here in Ecuador can cost as little as US$ 0.10. (I suggest asking to buy these from the local bakery.) These sacks are also often used to dispose of garbage, so they may be rescued by dumping their contents orderly into the garbage ... and given what we will be putting into them, they do not need to be very clean.

Weaving each container seems too laborious, especially if they will rot in use. It may be interesting to weave a basket made from non-biodegradable strips cut spirally from PET beverage bottles to hold the sack open.

Wax may be useful to protect biodegradable basket materials, but I would suggest that the container should best not be water-proof or air-tight, to allow excess liquids to drain into the soil under the toilet (or in some other organized way) thus reducing the production of odors and to allow oxygen to filter into the pile of feces to allow for normal, aerobic decomposition.

Is Gedek a type of bamboo?

Best wishes,
Chris

Hi Steve,

Not sure if this thread has gone dormant. But to answer your question, our first effort at local material-produced containers will be bamboo frame with woven split bamboo to make the basket. We think some can make themselves, others will have to barter or purchase (at low cost). Still working out the quantity of containers in a vault of the UDDT. Yes, they will eventually rot; but much less than the woven gedek, alternative material. We're looking into plastic woven bags; not yet sourced.

Hi All

I've been thinking about this problem and wondered if anyone has tried a wooden bucket, planter or similar container lined with wax for capturing solids? In most locations I would expect that such a container and a supply of wax could both be locally sourced and then manufactured onsite.

I understand my idea probably has flaws but perhaps it might inspire you guys to think of something new.

Thanks
Steve

Dear James,

I am glad you find useful the idea of storing feces in woven polypropylene sacks.

In our system, we tend to change the sacks when they are entirely full, often after about 2 weeks, but it would be better to change every week, before the sack is too heavy. For this reason, I suggest that the changing of the sack be integrated into a weekly schedule ... and there is no problem if the sack is not full.

(Our number of users is greater and more variable and we have 2 UDDTs. Plus your family of 5 would likely include small children, who do not contribute much volume. The type and volume of cover material is also an important variable, of which we use a cup of dry soil with each deposit. Yes, we store the feces for one year, for more peace of mind and more drying, although 6 months seems to be sufficient to eliminate Ascaris eggs according to trials we have done.)

For a family of 5, I would recommend changing the sack once or twice per week, which will require 52 or 104 sacks, if they are stored for a year for extra security, at an investment of only $5.20 or $10.40, if you can buy used flour sacks for $0.10 in India, as I do here in Ecuador.

Given the dry tropical climate in southern India, it is likely that 6 months at ambient temperature would be sufficient, which can be tested by searching for Ascaris eggs under the microscope. In this case, only half as many sacks would be necessary: 27 or 52 ($2.70 or $5.20).

If the shed for storing the sacks is built such that it functions as a solar oven, the number of sacks, the detention time and the storage volume could all be greatly reduced.

I suggest that plastic bins that are just the right diameter for receiving the sacks would be the most practical item for holding the active sacks open in the "line of fire".

Best wishes,
Chris Canaday

Dear Chris Canaday,

Thank you kind sir for your most helpful reply. I am very grateful. Woven polypropylene rice sacks do seem to be the best fit for this assignment. Based on conversations with other engineers and practitioners, I proposed to Lucas a design that uses a movable frame for the sacks. Your comment affirms this decision.
A few questions for you: if the sacks are changed weekly in your system, were they being filled and aged for 12 months? I am still determining the precise number of sacks needed for a rotation of a 5-person family for one year.

Thank you again.
Sincerely,
James Collector

Dear James,

Thank you for bringing this discussion to the forum.

Please explain more on the reasons for avoiding plastics. I agree that it is environmentally damaging to make new plastic, but if we use existing, "waste" items it is not so bad. Plus plastic is ideal for these containers, as it is inexpensive, long-lasting and does not rot in contact with the feces.

As Elisabeth mentioned, I use (and promote) woven polypropylene rice sacks as containers for the feces. These are extremely accessible and inexpensive, in fact good sacks can often be rescued from the garbage. They permit gas exchange, with water vapor getting out and oxygen getting in, in very much the same way as the very expensive breathable sacks discussed in the recent webinar. These can be reused year after year, if they are good quality sacks to start with and are kept out of the sun (since UV damages them). It is also important to keep rats under control, which is a good idea anyway.

I buy these sacks at the local bakery for about US$0.10. They are cheapest here since most people do not want dusty flour sacks, but this remaining flour is just more absorbent material in the UDDT. For the same reason, it is not necessary to wash sacks between uses.

I place the sacks as a liner in a plastic bin or bucket (roughly 20-40 liters in size), with holes in the bottom to allow for drainage of any excess liquid, which could simply soak into the ground or into a sack of sand, sawdust or rice hulls (from which it can evaporate out or continue to soak into the soil). This leachate is mostly due to cases of diarrea and, even then, seems to be in small quantities. In any case, it is good for this liquid to leave the sack immediately to avoid production of smell and to prevent liquids coming out when changing and storing the sacks.

The sacks should be marked with the date and stored in a place protected from the sun and rain, such as under a house build on stilts. Sticks or stones should be placed under them to allow for ventilation and to prevent moisture from the soil traveling up via capillary action. I suggest placing them horizontally, forming one-meter-cube stacks. It may be optimal to put sticks or perforated pipes between the layers to allow for more ventilation.

Optimally, these sacks could be changed every week, as part of a weekly routine, before they get too heavy (thus anyone could change them). Also, any fly eggs that get laid during the week would not have time to develop and emerge before the sack gets tied shut.

Choice of cover material is also key and merits more consideration than it often gets. Optimally, it should not only cover, but also absorb liquids, control flies and inoculate the pile with decomposer microbes. We should also avoid constant transport of materials to and fro, especially in urban or isolated locations. For these reasons, I recycle the safe, finished "bio-solids" as cover material (usually after a year of storage, here in the Amazon). Contrary to what people may imagine, this occupies all of the finished bio-solids, and I currently need to replace the lost volume from the original sawdust decomposing, which I do now with rice hulls. (Rice hulls are a great material for this, since they allow for more air flow in the pile and do not break down quickly.) We have not had much trouble with our users in the public tourist destination of the Omaere Ethnobotanical Park (omaere.wordpress.com), since this cover material has no bad smell. Plus, if the user feels that she has gotten her hands dirty by adding this dirt, it will help her to remember to wash her hands afterward (!). (And ways to add the cover material mechanically are being worked out.)

To get started, I would recommend mixing 50% rice hulls with 50% dried human or animal feces, compost and/or rich soil. Maybe include some biochar, too.

JKM, the wheelbarrow option seems too expensive and too vulnerable to the metal rusting. The organic, one-time-use containers are a good idea (but possibly too much work for the users to make them every time).

I invite any comments, corrections or suggestions. I wish you great success with Lucas, who has made great contributions to this forum.

Best wishes,
Chris Canaday

Another option is to make the temporary container more convenient and safe to handle the feces. In the composting toilets built by my current funding organisation in northern Uganda a kind of wheelbarrow is used (see attached picture), that has a drain for excess liquid and allows for very easy and safe transfer to the composting site.

I think the 432kg are rather an upper estimate (that's about 250g per person and day); for UDDT storage (as you are probably aware) the loss of weight due to loss of liquid (up to 75% of the total weight of the feces) also needs to be accounted for, as well as the material that is added (ash usually adds the least weight, but does little to speed up the drying).

There has been some success in using cheap woven plastic fiber bags, but I don't know if that fits to your "non-plastic" requirement. The basket posted above seems to be too fragile (at the connection between the bottom and the container walls most likely) and suspect to quick rotting though.
Maybe something woven out of thick bamboo or rattan stripes would do? Or how about something made from some layers of (plastic coated?) chicken-wire (with a thinner mesh in between)?

Edit: how about something made of woven banana leaf (maybe one time use only?) like this: www.artificialplantsandtrees.com/mm5/gra...002/GFT1021-ZM-1.jpg

or a simple bamboo basket like this:
cdn01.mightyleaf.com/resources/mightylea...sed/97040.a.zoom.jpg

Dear Elisabeth,

Thank you for the helpful and welcoming reply. Yes, I am excited to assist Dr. Lucas Dengel.

To answer your questions: My assignment is to research non-plastic options, partly due to the way plastics break down. 260 USD is the given ceiling budget; we aim to use much less per for the container-costs per UDDT. Rice sacks seem to have advantages in that they are air-permeable and can be dried and washed between uses. Do you know how durable they are?

Another concern, based on the calculations in box 1 on page 18 of the GIZ UDDT review, a family of 5 produces 432 kg of feces per year. This is 150 kg more than my calculations. For the removable container to weigh less than 45 kg, approximately eight containers would need to be used in rotation. So many containers is concerning for the following reasons: 1) material costs; 2) construction [eight containers x 20 UDDT]; 3) user simplicity - keeping track of which containers have been stored long enough.

Storing the containers will require additional space. Other designs use a smaller removable container which is frequently emptied into a secondary, processing site. This solves the costs of numerous containers but brings up further questions.

Kindly,
James

Dear James,
Welcome to the forum and thanks for your nice introduction.
I have moved a related post about UDDTs by EcoPro to be in the same thread as yours. You will be working with Lucas Dengel then?

Just to be sure: have you read the UDDT technology review by GIZ (susana.org/lang-en/library?view=ccbktypeitem&type=2&id=874)?
We have discussed the document at length in this thread here:
forum.susana.org/forum/categories/34-uri...mit=12&start=12#4133

In the same thread you will also find information about those woven baskets that are used in UDDTs in Uganda:

Faeces basket in vault. Vault door missing (stolen). Note urine on the ground. by Sustainable sanitation , on Flickr

and also about those rice sacks that Chris Canaday is using in Ecuador.

Do either of the two options appeal to you?

Why have you decided that plastic is not an option?

Also I don't understand your budget figure: 260 USD seems way too high for just the containers. Did you mean 260 USD for the entire UDDT? That would make more sense to me.

Just a little correction, you spoke of the "compost process" in the UDDT. It is rather a "drying process" though. Please see also here where we spoke about composting versus drying in UDDTs (yes, a small amount of composting can occur in your chamber but this will not be your main aim; you main aim will be drying):
forum.susana.org/forum/categories/70-com...composting-processes

Do come back to us with more questions or information / updates.

Regards,
Elisabeth