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

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

Some questions on my mind that the Susana community will hopefully be able to help with.

While we've seen a plethora of studies strongly demonstrating the benefits of urine reuse, there are very few that make a case for the marginal benefit of dry feces reuse. Of the studies we could find, the following showed no statistically significant difference in crop yield by dry feces addition.
  • Guzha et al's 2005 study "An assessment of the effect of human faeces and urine on maize production and water productivity"

  • Mnkeni and Austion 2009 "Fertiliser value of human manure from pilot
  • urine-diversion toilets"

  • As well, Kutu et al. (2010) observed an increase in spinach yields only when faeces were applied in combination with urine.
Health risk is a concern as Corrales et al (2006) found that ecosan users in El Salvadore practicing reuse had quite higher rates of helminth infections than those without improved systems.

While I'm sure there is some agricultural benefit given the relatively high P and K in feces, the question on my mind is: Is it worth the effort, cost, and health risk to advocate fecal reuse in a rural setting when containment (by burial or other means) is usually an option?

Wouldn't urine reuse and fecal containment usually be the better strategy?

What am I missing or forgetting about in this analysis? Has anyone had their experience teach them differently?

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

Dear Chris,

Your research seems to be very solid.

According to various publications, feces hold nearly all of the disease risk, while only holding 10% of the nutrients.

I suggest that our best reuse of cover material with a small percentage of dried feces (after approximately 6 months in tropical countries or 12 months in temperate countries) is to use it again as cover material. Advantages include
--Not needing to ever search for more cover material, after the initial 7 or 13 months (this is key since many UDDTs fail due to lack of cover material).
--Containment of any potential lingering pathogens (as you say).
--Fewer smells and flies (at least according to my subjective experience).
--Innoculation of the beneficial soil microbes that decomposed the feces of previous cycles.

Richard Higgins (on Ecosanres yahoogroup) and Juan Carlos Calizaya (CENCA and ECODESS publications) promote this recycling of cover material.

This will be more acceptable to the general public when a pedal-operated mechanism is developed to bring more cover material and take the feces away, as Fioravanti, Henry and I are working on.

Best wishes,
Chris Canaday

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- is it worth the cost/effort of processing?

The main agronomic benefit from feces is the improvement of soil structure (increase of organic matter content of soils, build up of humus), and only to a lesser extend the fertilizing effect from nutrients contained in feces.
This benefit will be greater in poor soils, and much less in soils already rich in organic matter (as it is the case in our projects in Moldova, where they have rich Chernozem soils).

The main problem regarding cost effciency of feces reuse is that the quantities are quite small, and to have real effects in improving soils addtional use of compost of other organic materials would normally be needed.

I agree that in real life it is more useful to decide the question of reuse or containment (burial etc.) of feces based on practical criteria rather than on the theoretic benefits. If safe reuse is difficult to achieve and users are so not enthusiastic, I also would favor burial of the stuff.

Florian


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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 Chris,
you mentioned

"Health risk is a concern as Corrales et al (2006) found that ecosan users in El Salvadore practicing reuse had quite higher rates of helminth infections than those without improved systems."

Below I copy the results of the google search for the mentioned atricle:
onlinelibrary.wiley.com/doi/10.1111/j.13...56.2006.01737.x/full

Results:  Users of solar desiccating latrines had the lowest prevalence of enteric parasite infection. Double-vault, urine-diverting desiccating latrines effectively reduced the transmission of some pathogens, but may not achieve the conditions sufficient for the complete destruction of the more environmentally persistent pathogens, Ascaris lumbricoides and Trichuris trichiura. Contact with inadequately treated latrine biosolids was associated with an increased risk of Ascaris infection.

Conclusions:  Solar latrines were associated with the overall lowest prevalence of enteric parasitic infections. Members of households where latrine biosolids were used in agriculture had a higher prevalence of infection than those where biosolids were buried. We therefore recommend the promotion of solar latrines in rural areas of El Salvador over other dry sanitation systems, and recommend that stored biosolids not be used in agriculture.

Unfortunately I do not remember the full article any more. Reading the summary I got the impression that in general members of households where latrine biosolids were used in agriculture had a higher prevalence of infection than those where biosolids were buried, so no relation to Ecosan or not, just to use of biosolids (of whatever source) versus biosolids buried. That is very well known.
Concerning your question about the added value of the use of feces. We do have the experience that in very sandy areas or rocky areas the use of the treated feces is very welcome. In these areas it seems to have an interesting effect.
To Chris Canaday: Chris, I personally dislike the “reuse” of feces as cover material. It might theoretically be possible to do so without danger when you use a biologically dead material, as it is done in the ECODESS experiences (they put lots of lime = pH very high = no biological activity). In this case there is no possible influence on the inoculation and I admit it is only my personal barrier that I for myself would have a problem to use it. But if there is still biological activity, in this case I think it is dangerous to use the material. For me the circuit would be too short.
My favorite is the centralized collection and treatment of material. By this you can afford to obtain a good control of the process.
Yours
Christoph Platzer
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  • Chris_Quintero
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

All: Many thanks for your input thus far- it'd be great to keep the discussion going!

Christoph: To your question regarding the correlation between feces reuse and helminth infection, attached are the 2003 and 2006 papers directly addressing the issue. In short, yes- they did find a correlation of composting latrines and increased helminth infection over pit latrine users whether reuse was practiced or not.

Has anyone else seen similar studies confirming/contrasting these observations?

Best,

~Chris


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Note by moderator: We deleted the second attachment because it looked like an article with copyright, however you can can use the following link instead to view the full version of the article: onlinelibrary.wiley.com/doi/10.1111/j.13...006.01737.x/abstract

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

Chris,

The Howard Higgins system generates and reuses cover material in 60 days!
This is the key to no vent pipes, solar hook up etc .,etc.,

Andrew Loxham of New Directions Foundation is also working on the pedal/lever operated organic flush system, for posh loos. The basic model is already there from a Finish company.
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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 Chris thanks a lot for those links. :cheer: I was looking for tha article since a longer time, had it once but somehow I lost it. There was something tricky about reading those data but I can´t remember the trick. In the Ecosanres group there has been a larger discussion about the higenic point about 1,5 years ago. Do you have acess?

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

Dear Chris,
I kept on digging.
The discussion I mentioned in ECOSAN res was in April 2009 (message 4188 and following). The article mentioned by you has been mentioned there as well. Rereading the article I remembered the doubt I had. It was in regard to the sampling, as there is a strong correlation between pigs and ascaris as well and the two communities had present both factors. Than I remembered that I wrote to some people to get more precise data and got answers. Digging deeper, I found another article in my laptop cemetery :P. (I hope I´m not comitting any error in attaching it but it is very helpful). The below attached research is a very well researched comparison between UDDT and solar heating toilets with a very short detention time (it is in Spanish sorry). And this research shows clearly the prevalence of ascaris in normal UDDT even after longer detention times. So there is a need to be very careful in promoting the reuse of feces. On the other hand it gets clear as well (grafico 6b) that a heating for a short period is very effective against Ascaris. As I´m an engineer I´m not too familiar with the different species.
I hope that gives some more useful information.
Yours
Christoph

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

Hi everyone,

I have been reading the El Salvador study via www.watersanitationhygiene.org and just found a key bit of info. It says that feces were stored in these 2-chambered UDDTs (LASFs) for "weeks to months and then emptied" (page 1822). Here is the key flaw and this explains the people getting worms: THEY WERE NOT RIGOROUSLY STORING THE FECES A SPECIFICED AMOUNT OF TIME SUCH AS 6 MONTHS!!!

The same slopiness (or haphazardness) applies apparently to the solar units, so presumably they sanitize the feces faster ... but maybe they were storing the feces longer, who knows?

We need to promote more testing of helminth egg die-off over time under different conditions of cover materials (sawdust, rice hulls, soil, ash, recycled cover material, mixtures, etc.), in the different climate regimes of the world. There should be universities interested in this and hopefully funds from somewhere to fund this.

Best wishes,
Chris Canaday

Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com
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  • muench
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Re: Health risks Benefit of Dry Fecal Matter Reuse

Dear all,

This seems to be the topic of the Chris's, we have here Chris Quintero, Christoph Platzer and Chris Canaday. :-)

I first wanted to ask Chris Quintero: can you please tell us a bit more why you asked this interesting question? I.e. how is it related to your work and your experiences? I googled your name - are you the one with the company Sanivation in Chile? Would be great to hear a bit more from you on the background of your question and your own experiences.

In general, I am with Florian Klingel on this one: I think in theory it is clear that faecal matter is good for the soil (this is kind of intuitive, too, isn't it? We take from the soil (food) and we give back to it); it has been shown that the results are best when both faecal matter and urine are applied. But this is just the nice agriculture side. In practice, if people are not positive about the idea and if they are (a) not willing to listen carefully to the trainings and to apply all the right safety precautions, or (b) not willing to pay someone else to do it safely for them, then let's just leave it (and go for the simpler burial route - although even here the person emptying the vault has to apply basic safety precautions).

Actually, shallow burial and planting fruit trees nearby is still a form of compromise, isnt' it?
I think reuse is nice, but it should not be forced upon each situation - whatever fits.

Design of UDDTs (urine diversion dehydration toilets)
I think it would be a fallacy to think that UDDTs can kill all pathogens completely. Perhaps in theory, but most likely not in practice. They will certainly achieve a nice and good pathogen reduction (the longer in the vaults, the better), but as an engineer I would not want to rely on the UDDTs themselves for total pathogen reduction (too much possible user error...). So therefore, one always needs to apply the WHO multiple barrier approach to the vault emptying and the possible reuse or the disposal (WHO, 2006). Educating users, wearing gloves, applying it at the right times and in the right way and so forth.
In case someone doesn't know this guideline yet, see here:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1004

The El Salvador study: Both publications (the one from 2003 and the one from 2006) come from the same research study, as far as I can see. (by the way, I am not sure if the 2006 journal paper is allowed to be placed online in a forum - copyright issues? That one from 2003 from the GTZ Lübeck conference is fine) If it was a wide-spread trend that UDDT users are less healthy than other toilet users then surely we would have seen more studies come out since 2006.

UDDTs users being healthier?: One study that points in the other direction (i.e. it showed that people in the Durban area who had received water and sanitation interventions with UDDTs had less diarrhoea then people without the intervention) is this MSc thesis:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1169
(OK, it is not able to delineate between the water supply and the UDDTs)

If you don't have time to scan the whole thesis, here is the project description on 8 pages as a SuSanA case study:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=791

It is important to note that with these 75,000 (!!) UDDTs, faeces and urine are actually not reused; but nevertheless, the users have to empty their faeces vaults regularly or pay someone to do it for them (and this could theoretically expose the emptiers to health risks), so I think it is worth mentioning it here. Here, they bury the dried faeces somewhere nearby (peri-urban areas, so enough space).

Microbial exposure and health risk assessment:It is also worth mentioning this new publication by SEI (final version to be released soon), which attempts to compare all the health risks of all the different sanitation systems:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1236

Stenström, T.A., Seidu, R., Ekane, N., Zurbrügg, C. (2011). Microbial exposure and health assessments in sanitation technologies and systems - EcoSanRes Series, 2011-1, Preprint draft. Stockholm Environment Institute (SEI), Stockholm, Sweden.

Perhaps it will shed some light on these questions.

Finally, I have a question back to Chris Canaday: You mentioned using the dried faeces as cover material. Do you mean the cover material (one scoop) that is added to the UDDT vault after each defecation event? Surely this amount is anyway so much smaller than the entire amount of dried faeces that it would not be a method of "getting rid of" the dried faeces. Or did I misunderstand?

Kind pathogen-free regards,
Elisabeth

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

christoph wrote: On the other hand it gets clear as well (grafico 6b) that a heating for a short period is very effective against Ascaris. As I´m an engineer I´m not too familiar with the different species.


Just a short comment on that: Ascaris has the eggs with the longest survival time of all helminths(up to 3 years) in the environment, that is why they are used as an indicator for helminths. They need a certain time in soil (optimum in warm and moist soil) in order to mature and become infective to people. That means by using feces for fertilzing, we do exactly what the worms need. Protection measures need therefore be carefully designed and implemented:
Measures are:
- long storage with conditons unfavorable for surviving (dry, high temperatures)
- heating for several hours.
- protection measures during reuse, keeping in mind that the people handling the feces and farmers are the groups most at risks, less so the consumers of the products.
- regular deworming of the populations


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

Definitely if fecal reuse poses health risks then no ways to reuse it. But it is not fact we can reduce the health risks (kill the pathogens) by various means ...... We successfully vermicomposted human feces and developed the vermibins capable to degrade the fecal matter in 2-3 days and turn it into very much valuable organic fertilizer. Additionally the urine can also be made pathogen free by various means -- like passing through UV ...

Hope your questions are answered, even if u need further clarification then u can act accordingly ..

With Best Regards,

-pranveer

---
Dr Pranveer S Satvat, PhD (IITK), FIE, FSED
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Environmental, Water Res. & Transp. Eng. Division
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Save the Nature that Nurture Us..

Dr Pranveer S Satvat, PhD (IITK), FIE, FSED
Professor
Environmental Engineering Division
School of Mechanical and Building Sciences
VIT University, Vellore -632 014, India
Voice #+91-416-220-2241, Cell #+91-9486961799
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Save the Nature that Nurture Us..
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