Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

  • daneric
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Chris Quintero,

Thanks for links and comments. Initial investigation shows it would be profitable. Biogas used at the school to replace LPG. Biofertilizer will probably have to be given for free, little market since diluted in water. A revenue not included so far is saved need of septic tank emptying, about 200 $/year for our 250 pupil school.

Yes, circulation pump for heating water missing. We had another idea first...

Important to emphasize, energy for heat treating wastewater is less than energy in its biogas potential, if very low flushing toilets are used.

I agree that UDDT toilets are good and to prefer if ability/willingness to make investment is limited. But otherwise it should be good with AD of waste water even in smaller scale. For larger scale I don't know how it is in your countries but in Sweden, AD and biogas production in municipal waste water treatment is becoming standard practice.

There are about 50 public toilets operational today in Nairobi and around that produce 10Nm³/day biogas from load of about 400 visits/day. Investment cost about 5000 $. Value of biogas, since directly replacing LPG for cooking is about 2000 $/year. Only flaw is that hygienization is not quite proper.

Maybe this is a bit off topic though...
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  • Marijn Zandee
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear all,

The question here is a good one and one I have been wondering about myself.

Based on the reports mentioned and the actual use in practice of UDDTs that I have seen (in Nepal at least) I strongly doubt that all pathogens will die off in the storage chambers.

I agree with the postings above that the main benefit of faecal matter lies in its use a soil conditioned, but saying that it contains only 10% of the plant nutrients is also not really a valid argument. It does contain a much larger percentage of the phosphate humans excrete, which is the mineral that in a resource sense is the most urgent for recycling.

My current view is that the best options (until we have better data on the sanitation in UDDTs) are:

1). Use in a pit on which a (fruit) tree is planted.

2). Co-compost in a vermi composting process, which I think is a very beneficial technology to introduce anyway.

It will be interesting to read the study comparing various sanitation options and their health "hazzards". I find it hard to believe that the water from a normal waste water treatment plant is completely ascaris free.

regards

Marijn

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  • christoph
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear all,
just two aspects I saw in some previous posts and this last one.
a) some years ago I consulted an earthworm sepcialist because the subject was discussed - Ascaris is NOT destroyed by Vermicomposting. The eggs leave the "vermis" without damage. So vermicomposting does not make the material save.
the reference:
Edwards C A, Bohlen P J (1996) Biology and Ecology of Earthworms. Chapmann & Hall p.224

For instance, the eggs of Ascaris suum and Ascaridia galli passed
through the intestine of individuals of 1. terrestris without damage
(Bejsovec, 1962). In this way, the eggs are spread throughout the soil,
wh ich facilitates infection of domestic animals and birds. The virus that
causes foot-and-mouth disease can persist in the musde tissue of earth-
worms for 7-8 days and remain virulent.


b) treated drinking water (if not treated very badly) is ascaris free. A filtration is an effective mean to eliminate Ascaris.

Yours Christoph
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  • Florian
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Marijn Zandee wrote: It will be interesting to read the study comparing various sanitation options and their health "hazzards". I find it hard to believe that the water from a normal waste water treatment plant is completely ascaris free.

christoph wrote: b) treated drinking water (if not treated very badly) is ascaris free. A filtration is an effective mean to eliminate Ascaris.


For wastewater, besides filtration (in constructed wetlands), the best available treatment to remove helminths is pond systems (retention time > 10 days), where eggs settle on the bottom. Eggs accumulate in the sludge of ponds, management of this sludge then is similarly challenging as solids from dry toilets or other fecal sludge.

Normal wastewater treatment such as activated sludge is not effective to remove helminths, time in settlers is too short for eggs to completely settle.

Removal of helminths from wastewater is currently only seriously considered when effluent is to be used for irrigation, as this implies a high risk to farmers exposed to the fresh eggs brought into the soil.

In richer countries, wastewater contains very few helminths, because the infection rate of the population is very low. Deworming of people is relatively easy, if a functionning health care system is in place.

In the context of ecosan projects in developing countries, I think deworming campains could or should also be an important component to minimze transmission risks.


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  • Marijn Zandee
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear Chris,

Thank you for correcting me there. This is very important (if unfortunate) information. I will try to find the article, however can you confirm in the meantime for which worm species the research was carried out and if there is a good reason to assume that this would also be valid for E. foetida worms?

rgds

Marijn

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  • canaday
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Re: Benefit of Dry Fecal Matter Reuse- Recycling of Cover Material?

Hi everyone,

At the risk of seeming too insistant on this point, I would like to clarify and reemphasize the potential for reuse of sanitized (= pathogen-free, not necessarily sterilized) cover material from a previous cycle.

I would also ask each to reflect on whether his or her responses are based on science and logic, or rather "gut reactions" and societal norms (especially when mechanisms are developed that avoid the user having to scoop and aim manually).

What I refer to is the reuse of cover material including the feces from a previous cycle, which have been rendered free of pathogens by whatever acceptable method (storage with ashes for a long enought period, Chris Quintero's solar ovens, thermophilic composting, etc.)

I mention 6 months for the Tropics and a year for the Temperate Zone, as I thought such a consensus was forming, but, if with research it is shown that other times are more appropriate, then the guidelines should change. I think we agree that the key thing is for any Ascaris eggs that may be present to die, as they are the most resistant.

Does anyone know why the table on pathogen die-off over time was dropped between the 1998 and 2004 versions of the Ecological Sanitation book? More research on this needs to be done with different cover materials and in different climates.

Our colleague, Vishwanath Srikantaiah of India, offers the following thoughts about this:

Dear Chris,

That seems an entirely possible proposition though have not seen it being tried or tried it myself.
In a situation where there is no cover material or even when there is and when you want to speed up the process I guess this will make eminent sense.

(My favourite composting material is vermi-compost which has earthworm eggs already in it and therefore quickly decomposes ecosan material too.)

Regards,
Vishwanath


The point is to make the material safe and then reuse it ... and this is just one more option for reuse ... if we really believe in our guidelines. Only as a last resort should we enclose and dispose of this.

As I mentioned before, many times good cover material is scarce and UDDTs fail due to this scarcity. This may be especially acute here in Ecuador, where cooking gas is heavily subsidized (a 15 kg tank only costs US$1.60 at the depot or US$2.50 delivered) and everyone (except for those in in isolated communities out in the jungle) cooks on it and does not generate wood ash.

Yes, Christoph, I know that Juan Carlos Calizaya adds mineral lime to this recycled material before reusing it again ... but he once told me informally that this was largely as a psychological "techno-fix" for the peace of mind of the users. (Juan Carlos, any other comments or suggestions on this?)

Chris Quintero, congrats on, and good luck with, Sanivation ( sanivation.com/ ). Why do you say on your blog that your solar toilets and ovens do not decontaminate the feces? If baked long enough, do not all of the pathogens die? I think the solar ovens are an especially good idea in the case of properly trained service providers who work on the level of the neigborhood or entire city, as this arrangement would hopefully ensure proper application of the guidelines. How well would the solar ovens work in cloudy places like here in the foothills between the Andes and the Amazon?

By the way, I think the key to profitable and hygienic recycling of these nutrients may be that such service providers apply them in agriculture themselves (possibly in partnership with farmers), to later sell beautiful, tasty fruits and vegetables on the open market ... instead of marketing repulsive pee and poop and hoping that everyone follow the hygiene guidelines.

Elisabeth, it seems that the volume of recycled cover material is similar to that needed to cover new feces in the new cycle, as (at least here) the feces largely disintegrate, leaving the largely the sawdust and ashes of the previous cycle.

Best wishes,
Chris Canaday

My goal in mentioning this recycling is to encourage research on this.

Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com
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  • Florian
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Re: Benefit of Dry Fecal Matter Reuse- Recycling of Cover Material?

canaday wrote: At the risk of seeming too insistant on this point, I would like to clarify and reemphasize the potential for reuse of sanitized (= pathogen-free, not necessarily sterilized) cover material from a previous cycle.


Hi Chris,

If the material is free of pathogens, then your proposed system is ok of course. But what if the material is not totally free of pathogens? Then this system exposes the users to quite some risk, as the material passes more less through their hands.

I think in practice the risk of not optimal treatment of feces is a realistic one in most cases. Even if we know exactly how to treat feces to render them pathogen free (e.g. which storage periods to respect) it always depends on how users actually do that. Many things can go wrong here, so I think it is risky to recommend a system that depends on 100% compliance of users with rules for operation in order to exclude direct exposure of users to pathogens.

In my opinion, it's always wise to foresee several barriers and not solely rely on one (treatment). Minimizing all direct contact of people with fecal material would be another barrier that protects the people, even if the treatment is not done perferctly according to instructions.

So no, I don't think it's purely gut reaction, more reasoning along the multi-barrier concept recommended in the WHO-guidelines.

Best regards, Florian


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  • christian.rieck
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear all,
I would like to add on this discussion even though some time has passed already. It concerns the Acari die-off in dehydrated faecal matter from dehydration (double) vault UDDTs. It was discussed here to quite some detail.

While writing the " Technology Review on UDDTs " (dehydration vaults only) we came to the conclusion that full pathogen removal cannot be achieved in the dehydration vaults. The same seems true for the guidelines values of WHO (≤1 helminth ova per litre for unrestricted use in agriculture) after storage of 1.5-2 years at 2-20°C and >1 year at >20-35°C. There is simply not sufficient research to prove that the storage in dehydration vault will render the faecal safe with regard to Ascaris. Not to forget the human factor that puts the whole treatment at high risk of failure or insufficiency. That is also what Florian has mentioned in his last post. Thus we have focused on the fact that it is more reasonable to have a dry and odourless faecal matter after 6 months of storage which can be easily emptied and is relatively safe to handle if additional barriers are applied (i.a. protective wear, handwashing and burial of material).

The research available usually deals with faecal material that has been stored in the vaults for 6 months to max. of 1 year after the last addition of fresh faeces. All research shows that Acari eggs still remain in higher numbers in the UD-waste (e.g. Buckley et al. 2008 ) - Christoph had shared this document earlier in this discussion, thanks). Please correct me if I am wrong.

Now my question is on how we can define what safe handling of faecal matter from dehydration vault UDDTs really means (emptying, transport and burial or post-treatment processes)? Can we argue that dehydrated faecal matter that we want to dispose may have higher Ascari counts than the WHO values require for unrestricted use in agriculture? Since we still need to handle the material there is surely a remaining health risk. If additional barriers are applied as mentioned above it should be fine. But will the people who handle the waste, really implement those barriers and if not do we then expose them to an unacceptable health risk?

Or would would it be better to have a prolonged storage times as proposed by WHO of 1.5 to 2 years (and spend more money for construction) in order to lower the health risks significantly? Considering that the human factor is hard to control (vaults fill up faster as expected, no covering material is used, water has enters the vault etc.) I do not see that advantage.

Best regards,
Christian

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Reform of the Urban Water and Sanitation Sector (RUWASS)
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  • Marijn Zandee
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear Christian,

I agree that there is substantial evidence that Ascaris survives dehydration vaults. Also I doubt whether increasing the storage time would really be a 100% guarantee for die off.

Further the usage of dehydration vaults by toilet owners is not always correct, so faecal matter can be removed to early or not be fully dry.

Which leads to the conclusion that some for of post processing is required, unless soil burial with tree planting can be considered safe?

As stated earlier in this discussion, Vermi composting is not a good solution, as Ascaris eggs do not get destroyed as is commonly thought.

Therefore I think heat processing is the only viable way, for which I see 3 options at current.

1.) Probably most widely applicable: Thermophilic composting. For instance in composting piles as designed by Jim Jeavons for his GROW BIOINTENSIVE experiments. (Jeavons J. How to grow more vegetables on less land then you ever thought possible on less land then you can imagine.) Also in the "Soil guideline to ecological sanitation" there is a good description of centralized composting. Having one centralized composting plant in an Ecosan village would help insure actual post processing.
The advantage of training people in a thermophilic composting system is that the compost would probably be of higher quality then local practice and as such may ensure take up by farmers.

2.) Some form of solarisation, the same way as nursery soils can be solarised to help sterilize them. This process will be very difficult to control though, and will only work in hot dry climates.

3.) In places where biomass stoves are promoted (such as top draught stoves and rocket stoves. Maybe the dry feacal matter could be added? I don't think anyone has tried that yet though. Or it could be added to charcoal producing processes (see attached file)

Further, for the handling of dried feacal matter there may have to be some common sense guidance. Gloves, facemask and handwashing.

I also think that if we think we can not motivate and trust the community to re-use faecal matter in a safe way, then we can also not do this with urine and thus ecosan becomes a dead end.

Kind regards

Marijn Zandee

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  • AFoote
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Thanks for adding clarity to the Ascari egg die-off discussion Christian. This health risk is exactly why we have been working on solar sanitation.

Christian we struggled with many of these questions regarding health risks, user involvement, external human factors and at the same time trying to find a viable business model. All these factors combined made us decide on a service model towards sanitation (imagine instead of paying to build a toilet, paying much less on a monthly basis for a clean and serviced toilet at the household level). There are lots of benefits here: lower initial costs to user, toilets are properly maintained by service provider, servicer providers are trained and use proper barrier techniques, service is flexible to specific user needs, works in flood prone or rocky areas, it is attractive to users who are migratory or plan to move soon, and includes adequate treatment. We call this our desirable service model.

We plan to provide a desirable sanitation service across the entire value chain, from containment and treatment to reuse, that is affordable to people earning less than $2 a day.

Marijin and others, I encourage you to check out our website, www.sanivation.com which has brand new video detailing our solar system and service model.

We have gotten great results with helminth inactivation via our solar concentrators at greater than 99% inactivation in less than a day. We will be publishing our results in the coming months. In the meantime see a video of our experiment here ( sanivation.com/so-does-this-solar-concen...thing-kill-helminth/ ) and other pictures of our implementation are also up on our blog.

The good thing about solar sanitation is it doesn't need to be super dry and hot. Most countries that lie within 15 degrees of the equator get significant sun for solar sanitation. This also happens to uniquely coincide with a majority of the countries that have high death rates due to sanitation related diseases (see map in attachment).

We are just finishing up in Chile and looking to move to an area of greater need, like Ghana, Kenya, India. I've attached an outline of our work for sharing. Does anyone know of any good on the ground, sanitation market creation groups we should speak with and potentially collaborate with?

Cheers,
Andrew

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  • Marijn Zandee
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear Andrew,

The concept looks very interesting, I assume you collect faecal matter from households and then solarize in a central location?

Could you share with us how much it costs for the families to hire a toilet and services? And is that cost covering for your organisation?

Kind regards

Marijn

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  • christian.rieck
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Dear Marijn and Andrew,
Thanks for your reflection on the Ascaris die-off in dehydration vaults. I hope to collect some more views on that. I also see the only viable and effective way to hygienise faecal matter in heat treatment.

The use of solar concentrators sounds very promising. How long must the sun shine for an effective one day-long treatment? How do you see the risk in mismanagement of the treatment e.g. removing the faecal matter too early from the concentrators? It is definitely a fast treatment however the space requirements seem to be quite big. I am trying to estimate if such an application for dense urban settlements like slums is an option. The transport distance for feacal sludge needs to stay short to keep costs for service providers at affordable levels for toilet owners. How big would a treatment site for a settlement of lets say 100,000 inhabitants need to be?

You are talking in your one page leaflet that the operational costs are 3$ per household and month. Are these values for Chile? Could you share with us each of the cost item you have considered for this calculation?

@ Marijm. I had also checked on this agricultural method of solarisation that is used to steralise the top soil. I heard from J. Germer (University Hohenheim) that their trail at the Accra in Ghana did not show promising results in terms of reliability.

The idea of adding dry faecal matter to a charchoal process is interesting. thanks for sharing that document with the oil drum (some things can be made so easy, great). I know that the colleagues of Susan design are working on a biochar system in Uganda. You might be able to find out more by posting on their facebook site www.facebook.com/pages/Sustainable-Sanit...n-Design/94883771645

And by the way your statement on the dead end for ecosan. Your conclusions are most logical. But if you think about the success stories (with some health trade offs) of excreta use in e.g. China, Japan and even European countries for centuries I do not see a dead end. They had found way of minimising the health risk involved (e.g. not eating raw foods).

Cheers
Christian

GIZ Uganda
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