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

62.2k views

Page selection:
  • Florian
  • Florian's Avatar
  • Water and Sanitation Specialist at Skat Consulting Ltd.
  • Posts: 269
  • Karma: 22
  • Likes received: 131

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

Please Log in to join the conversation.

You need to login to reply
  • canaday
  • canaday's Avatar
  • A biologist working toward sustainability
  • Posts: 400
  • Karma: 18
  • Likes received: 175

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

Please Log in to join the conversation.

You need to login to reply
  • Marijn Zandee
  • Marijn Zandee's Avatar
  • Moderator
  • No longer working in WASH, but still following the forum.
  • Posts: 261
  • Karma: 22
  • Likes received: 134

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
Marijn Zandee

E: This email address is being protected from spambots. You need JavaScript enabled to view it.

Please Log in to join the conversation.

You need to login to reply
  • Florian
  • Florian's Avatar
  • Water and Sanitation Specialist at Skat Consulting Ltd.
  • Posts: 269
  • Karma: 22
  • Likes received: 131

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.

Please Log in to join the conversation.

You need to login to reply
  • christoph
  • christoph's Avatar
  • Moderator
  • Sanitary engineer with base in Brazil and Peru, doing consultancy in other countries of LA
  • Posts: 309
  • Karma: 19
  • Likes received: 145

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

Please Log in to join the conversation.

You need to login to reply
  • Marijn Zandee
  • Marijn Zandee's Avatar
  • Moderator
  • No longer working in WASH, but still following the forum.
  • Posts: 261
  • Karma: 22
  • Likes received: 134

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
Marijn Zandee

E: This email address is being protected from spambots. You need JavaScript enabled to view it.

Please Log in to join the conversation.

You need to login to reply
  • daneric
  • Posts: 4
  • Likes received: 0

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...

Please Log in to join the conversation.

You need to login to reply
  • christoph
  • christoph's Avatar
  • Moderator
  • Sanitary engineer with base in Brazil and Peru, doing consultancy in other countries of LA
  • Posts: 309
  • Karma: 19
  • Likes received: 145

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

Dear Chris and AFoote,
as you asked three times for reactions to your question I will try to answer with a clear: I don´t know. :( Some thoughts:
- We build over 400 UDDT in Peru. In the mountain region, which is the region the people are very interested in the feces as well about 150, we had costs of about a 100 U$ for the whole toilet. This is due to the use of Adobe bricks (0 cost) and neighbourhood labor. In this case 150 US would be expensive, but on the other hand I do not see 150 US additional costs (I looked at the picture on your site). But even if the costs are the half… would it not be much cheaper to build a larger chamber? Especially if the mountain situation makes that possible without steep stairs. Another advantage is that you do not have the hazel with the direction of the sun in relation to the toilet. I always felt that the direction to the sun is a very limiting aspect.
+ The Ascaris point is important so why not invest by donors a little additional sum in order to secure the safe reuse? And in the rural area the available space makes the direction into the sun possible without being a very limiting factor.
- Wouldn´t it be better to invest in X U$ for a treatment for the people together with a good regular UDDT toilet? Once worm free the ascaris aspect is not important any more. I know ….that depends on the rest of the environment.
- Perhaps the pH option with a long storage is better as cheaper..the cost aspect is VERY important as we are talking about lots of people….and we when we are talking about 150 US / toilet or ..in 10 users (Africa) or 5 users (LA) about 15-30 U$/person.

+ On the other hand the discussion I know about suitable costs for mass application, is surrounding 50 -70 U$/person for the whole toilet (complete construction). Our costs for a complete toilet (Lima -Peru) build by a professional are about 100 U$/pe (just for a comparison - normally we only build the basic bench to bring down the costs, the surrounding has to be constructed by the owner of the toilet). So in the Mountain region with natural building material there might be room for a solar aspect (as it eliminates the necessity of a secondary treatment which would be necessary additionally necessary in the peri-urban and urban situation and has to be aded to the price of the toilet)
Sorry, not very clear and I´m pretty sure you already came to these conclusions. Having written these aspects, I would vote for no. I would save the money for more toilets.
Yours
Christoph Platzer
Rotária do Brasil
P.S. to Daneric.
There has been a post #447 in this forum from India about a solar solution for ascaris.

Please Log in to join the conversation.

You need to login to reply
  • Chris_Quintero
  • Chris_Quintero's Avatar
    Topic Author
  • Posts: 5
  • Likes received: 0

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

Daneric,

I've heard about two studies who used flat plate solar collectors to raise the temp of wastewater or fecal sludge- neither was designed for the sludge to hit temperatures as high as you're proposing, but the general idea seems possible. The studies are:

www.sid.ir/en/VEWSSID/J_pdf/102620110205.pdf
and
www.ipcbee.com/vol6/no1/87-F10043.pdf

I'd be very skeptical about the cost-effectiveness of such a system on a school wide scale (you say 250 people?) - especially if you're counting on making a profit off fertilizer/biogas sales.

That said, technically I see no glaring reason it wouldn't work. By your diagram however, wouldn't you need another water circulation pump between the panels and hot water tank? It looks like you have an evacuated tube collector drawn (who's circulation operates off a thermosiphon) but you'd need another pump to circulate that hot water to the tank below it.

Florian: I agree- nice summary of the options available- There will always be niche cases, but for the majority of rural users I think that's a good way of looking at the problem.

All the best,

Please Log in to join the conversation.

You need to login to reply
  • Florian
  • Florian's Avatar
  • Water and Sanitation Specialist at Skat Consulting Ltd.
  • Posts: 269
  • Karma: 22
  • Likes received: 131

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

Hi AFoote, thanks a lot for all this good information. I have yet to dig through all of your links, but your excellent summary posted here helps much!

AFoote wrote: The question I would pose is similar to a past one from Chris Quintero. What are peoples viewpoints on interventions that guarantee pathogen inactivation with an option of reuse and what would be an affordable cost for such an intervention?


On household level, I see basically these options:
- after removing dried feces / compost from chamber, additional storage outside on a safe place (e.g. coverd heap) for another 1-3 years; then reuse. This option is interesting when users anyway know of the benefit of bringing organics to the soil and already do composting of vegetal matter or similar activites where feces use could be included.
- no reuse but safe disposal (burial). This option is probably best when users have no real interest or need in using feces.

Collection systems would allow for more sophisticated centralised treatment (e.g. well controlled composting) and quicker reuse. If such a solution is economically viable can probably only answered case by case...

Florian

Please Log in to join the conversation.

You need to login to reply
  • daneric
  • Posts: 4
  • Likes received: 0

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

I'm currently in Kenya working for energy generation and nutrient reuse for schools. One idea is to have hot water from solar panels heat the slurry to 70C for about an hour to remove pathogens. The toilets are no flushing 'hole in the flor' style. Anybody heard about this kind of pre-treatment before and would like to share their experience?

The 'effort' of safe fecal reuse would in this case be about 0.14 kWh/person,day; heating urine, faeces and some cleaning water from 25 to 70 C. This is less than the energy of the potential biogas per person and day, 0.33 kWh. (this is though including potential from kitchen waste) Further, there is a big win cos biogas has much higher exergy content than heat at below 100 C; a lot more useful and valuable.

Shouldn't this be a nice thing to develop?

I've attached a preliminary plan, however the school project we were planning to build it for has run a bit low on funding so will look for another way to test it.

This message has an attachment file.
Please log in or register to see it.

Please Log in to join the conversation.

You need to login to reply
  • AFoote
  • AFoote's Avatar
  • Innovating sanitation solutions to meet demand from BOP
  • Posts: 16
  • Karma: 3
  • Likes received: 8

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

Hi All,

I have enjoyed the discussion. Thanks to my colleague Chris Quintero for starting it.

I wanted to add a few more resources and future outlooks on a couple points.

1. Reemphasizing the Nordin 2010 thesis "Ammonia Sanitisation of Human Excreta Treatment Technology for Production of Fertiliser." The thesis has a great in depth review and research on treatment technologies and their effect on pathogen inactivation. Here is a sample about composting:

"However, in the composting process, prolonged pathogen survival
despite a seemingly adequate temperature increase has been observed
(Germer et al., 2010). Non-homogeneous temperature distribution may
allow pathogen survival (Tonner-Klank et al., 2007) and re-growth in colder
outer zones (Elving et al., 2009). Frequent turning of large-scale composts
and insulation of small-scale composts can overcome such temperature
distribution problems (Germer et al., 2010; Niwagaba et al., 2009; Vinnerås
et al., 2003a)." (Nordin, 2010)

2. Another thesis done on pathogen inactivation in composting latrines not mentioned in Nordin review. This one done by Jim Mihelcic's team in Panama. Mehl, Jessica. (2008). Pathogen Destruction and Aerobic Decomposition in Composting Latrines: A Study from Rural Panama. Master's Thesis. Michigan Technological University

"The temperature results support previous findings that compost latrines do not get hot enough to kill pathogens; rather, the latrines remained close to ambient temperatures. The pH results show that many latrines were operating within the range for ideal decomposition, pH of 7.5-8.5 (Jenkins, 1994), but only 17% of latrines measured pH 9 or above, the recommended pH for pathogen destruction (WHO, 2006). Most composting latrine users added desiccant materials, sawdust and wood ash, to lower the moisture level and provide the necessary carbon for decomposition. However, it seems not enough desiccant materials were added because moisture levels remained above the suggested maximum of 25% for pathogen destruction (WHO, 2006) and C/N ratios were in the range of the ratio of raw human faeces. More importantly, the results of the microbiological analysis show various pathogens, mainly helminthes, still present in the compost samples that had been stored for the recommended 6-month storage time." (Mehl, 2008)


3. Viability of Ascaris and other helminth genera no larval eggs in different conditions of temperature, lime, and humidity .

Key takeaways are: To have excreta be free of helminth "a temperature above 70°C and 80% humidity for a duration of 120 min; and, (b) a 20% CaO dose (pH 12.5) and a humidity level of 80% for a duration of 8 months are needed. With regard to the resistance of different genera of helminth eggs. Ascaris, Toxocara and Taenia,
in that order, were the most resistant, while the most sensitive were Trichuris and Hymetiolepis" (Maya, 2010)

The study also includes a summary of all previous work on helminth inactivation. A highly recommended read for those interested in environmental conditions for pathogen inactivation.

4. WASH Benefits project research and proposal attached from 3ie. Research consortium looking to identify health benefits and sustainability of WASH interventions. This research will be a real game changer and is Gates funded.

5. Literature review from Sanitation Ventures that focuses on on-site waster characteristics, digestion and decomposition. Found here

This has been already been a very informative discussion. The question I would pose is similar to a past one from Chris Quintero. What are peoples viewpoints on interventions that guarantee pathogen inactivation with an option of reuse and what would be an affordable cost for such an intervention?
Andrew Foote
Co-founder
www.sanivation.com

This message has attachments files.
Please log in or register to see it.

The following user(s) like this post: Florian

Please Log in to join the conversation.

You need to login to reply
Page selection:
Share this thread:
Recently active users. Who else has been active?
Time to create page: 0.210 seconds
Powered by Kunena Forum