Incineration of UDDT waste at healthcare facilities - request for feedback

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  • EliWeber
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Incineration of UDDT waste at healthcare facilities - request for feedback

Hello SuSanA Community,

I've been working on a research project evaluating container-based sanitation at healthcare facilities in Kenya for the past year. The toilets are urine-diverting toilets (picture below). Urine and anal washing liquid is disposed of in nearby pits, or piped to septic tank. Garbage is diverted to a separate bin for disposal (see the pipe in the toilet picture and separate bin in sub-floor enclosure). 

So far, the poop and cover material (charcoal dust) is transported to a local facility for treatment and conversion to fuel products, which is great. A challenge comes when we want to evaluate the toilets at locations farther from the treatment and reuse plant. Being a healthcare facility, we are limited by onsite treatment options that might be possible in other contexts. We can't take up large amounts of space, or allow people to see or come in contact with faecal waste. Imagine how health officials would respond to onsite composting, for example. Being waste from a healthcare facility, there's heightened concern about pathogens and reuse.  

One option we are considering is a small onsite incinerator. It would eleminate any pathogens and dramatically reduce the waste volume without excessive handling. I've done some looking around and haven't found tons of information, and no successful examples of cases where faecal waste is directly incinerated. To make this option feasible, the UDDT waste would need to be directly loaded into the incinerator (no drying in the sun at a hospital) and burn with minimal offensive odor. We expect around 30-100kg of waste per week.  

We are considering using waste oil, diesel, or kerosene as a startup fuel to get it hot. One source ( www.susana.org/en/knowledge-hub/resource.../details/443?pgrid=1 ) found poop could be burned well above 850 degrees C, but only after drying in the sun. The moisture content of the waste will be less than fresh poop (due to added dry material), but still higher than ideal for burning.

Curious if anyone has any experience here or example designs. I wonder if there are some obvious reasons this hasn't been tested more:
  • Is burning wet poop, even at very high temperatures just not possible without creating a huge stinking mess?
  • Does it require elaborate controls or material that are not feasible in low-income contexts? 
  • Are there any other treatment options that might be preferable for onsite treatment/disposal at a healthcare facility?
Thanks in advance for your feedback,

Eli



Mechanical engineer and WASH implementer
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  • jhallowell
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Eli,

Biomass Controls has thermally treated UDDT fecal sludge in Alaska.  The UDDT's in use have a fan that dry the feces to 35% MC. We pre-process using a grinder and also add a little cardboard to increase energy. 

More information@ www.biomasscontrols.com
Jeff Hallowell
Biomass Controls PBC
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  • EliWeber
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Thanks Jeff,

Great to see some other groups working on the problem of decentralized waste treatment, especially with consideration of CBS. You've got some very well-developed systems for optimizing the combustion or carbonizing process. One of your presentations on the website hints at some ongoing findings with burning poop directly, even after thermal drying, such as un-reliable ignition and odor. Any lessons to share?  

To be an appropriate solution for this sort of context, we are interested in developing or deploying a much simpler mechanism, in the same ballpark as a De Montfort incinerator ( mw-incinerator.info/en/304_Mark_9.html ) that is very common here at healthcare facilities for handling sharps and other waste.

Biochar is a great reuse product, but given the small quantity of waste, it may be better to dramatically reduce the volume via incineration in this case. 

Have you learned any lessons you can share about wet poop incineration:
Combustion temperatures, poop feed rates, sizing and geometry of combustion chambers, airflow rates, or gas retention time at high temperature to reduce contaminants and odor?

Thanks!
Eli 
Mechanical engineer and WASH implementer
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  • tgurksi
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Hi Eli,

All of the systems that I'm aware of are either complex, or require external energy. To burn feces without external energy requires high efficiency and a means of drying the feces using the heat of combustion, which generally leads to complexity and cost. To burn it simply, external energy is typically utilized, which can be in the form of an external fuel that is burned, or dry material that is mixed with the feces. If the cost and supply chain of an external energy source is not prohibitive, this is probably the better choice for your application. At that point, the actual incinerator doesn't need to be anything particularly special, and there is probably a commercially available unit that would do the job. 

Cheers,
Tom
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  • Chaiwe
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Hi Eli,

This could be quite an interesting topic for research. I have done some looking around for information on small onsite incinerators and possible ways of drying wet poop without drying it under the sun, but i haven't come across relevant examples where it has worked successfully. 

Could it be that health facilities find incineration of UDDT waste onsite costly as mentioned, especially in the African region? Have you by any chance in evaluating container-based sanitation at health facilities come across some reasons why onsite incineration for UDDT waste is not considered by most health facilities?

Does onsite incineration offer more relevant benefits than offsite incineration/ treatment and disposal?

If it does could you kindly share some relevant examples that you have come across since you posted this topic?

Regards,
Chaiwe.
Co-moderator SuSanA forum
(Under consultancy contract with Skat Foundation funded by WSSCC)

Chaiwe Mushauko-Sanderse BSc. NRM, MPH
Independent consultant located in Lusaka, Zambia
Email: This email address is being protected from spambots. You need JavaScript enabled to view it. Twitter: @ChaiweSanderse

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  • EliWeber
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Thanks Chaiwe and Tom,

Here's a quick update on where this research stands at the moment. 

To our knowledge, container-based sanitation (CBS) hasn't been tested and evaluated at healthcare facilities. I suppose bedpans are a form of CBS, but they are normally quickly transferred to a toilet immediately. Incineration of medical waste is somewhat common, but not for poop. Healthcare facilities likely wouldn't even consider incineration of poop if they rely on pit latrines or septic systems. 

The reason we are looking at onsite treatment is because the treatment plant we've been sending waste to isn't close to some other facilities we would also like to evaluate. Transportation of the waste is a significant cost of managing CBS, so if we can do it all onsite, it improves the overall financial viability. It also allows us to keep everything in one location which is easier to manage. Regarding cost of treatment, we are looking to take the principles of higher tech incinerators and make an appropriate design - nothing electric, just simple welded or ceramic designs - otherwise it probably wouldn't be viable. Our thought is that an effective CBS system, coupled with a reliable incinerator could provide a long-term, sanitary, and cost-effective solution, but the incinerator component is the missing piece at the moment.   

It's possible that incinerating poop in its wetter form is too energy intensive to be viable. Using external energy is ok, within reason. We are in the early stages of testing this. We've found poop burns at around 400C surface temperature and burns well in a furnace of at least 725C, which is very hot. Cooler than that and it smoulders, which is slow and emits some odors. Breaking up the poop so it dries and has good contact with hot air is essential for faster burning. 

Thanks for your thoughts. I'll keep updating as we find out more.

Eli 
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  • tgurksi
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Let us know what you come up with!
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  • canaday
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Dear Eli,

I think that incineration of wet poop will always be complicated, expensive, and ecologically unsustainable.

I would recommend burying these feces in the bottoms of deep holes where trees will be planted. If no local people want to plant trees (or if a whole row of trees is to be planted, for example as a windbreak), the feces could be buried in trenches, possibly 1.5 m deep (staying well above the water table), and covered with about 50 cm of the excavated soil, thus there would be no problem continuing with normal farming on top of the filled trenches. For this, the bins that collect the feces under the toilet could be lined with dry banana leaves (or green ones from plants that have been harvested), which also go into the hole or trench, thus facilitating the cleaning of these bins or possibly eliminating the need to wash them at all. A vertical board could be placed in the trench to keep the material in the part of the trench that is being filled ... and then be moved gradually along the whole length of the trench. This can be done at a prudent distance from rivers or wells for drinking water.

This would:
  • encapsulate the material in the soil, eliminating any contact with it and essentially any risk of disease transmission;
  • improve local soils, contributing to better agriculture and food security;
  • generate work for local non-skilled laborers would do the digging;
  • sequester carbon into the soil, contributing to the mitigation of Global Climate Disruption.
The latter technique is called "Deep Row Entrenchment" and there is more info on this in EAWAG's Faecal Sludge Management book and in the following research paper from South Africa:
www.susana.org/en/knowledge-hub/resource...library/details/1679

I would also like to congratulate those who built and manage this unit on an especially tidy and presentable UDDT. Was the squat pan made in a factory or built on-site? Is the use explained personally to each new user or is an instruction sheet enough? Can you please post a photo looking straight down upon it?

Best wishes,
Chris Canaday
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com
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  • jhallowell
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Dear Eli,

It has been our experience from testing, that feces will volatilize between 483.3 °C and 500.6 °C.  Our system feeds continuous between 9 and 33 kg per hour.  Feces does have enough energy to dry and pyrolyze. In fact the energy balance is quite good for feces and very good from UDDTs since it dries a bit.  Typical end of torrefaction and beginning of pyrolysis is 300C and ends around 900 C.   Carbonization for feces is the best way to preserve nutrients and does not cause a hazardous waste such as ash.  A TLUD is a simple system that can be used.  Also rotary systems can work well.  We have also found that the processing of menstrual waste is easy and begins to volatilize around 374C.  Making biochar from organic feedstock is easy and best to make healthy soil. Our systems are continuous and priced about $0.01 per person per day from 10 people - 30,000 people but many batch and kiln systems are very inexpensive and simple to make and operate.
There are many videos on TLUDS and other style kilns.  Here are a few links:
.  
 
Dr Paul Anderson is a great resource and always willing to advise.

Kind regards,

Jeff
Jeff Hallowell
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  • EliWeber
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

Thanks for the excellent feedback Chris and Jeff.

The UDDT toilets are concrete, manufactured onsite. A closer photo of a freshly constructed interface is below. The toilets are cleaned and containers are emptied every day in the morning before patients arrive. There is also a dedicated staff member onsite for user education and hygiene promotion, as well as data collection. There are also posters inside the toilet to remind users about adding dry material, liquids separation, and to put garbage in the chute, not the poop hole. So far, we've gotten some very nice data showing people like the toilets, largely because they are cleaned regularly and don't smell.     



Regarding the trenches, it's a great and simple idea. Could be a great reason to reforest a hospital! I agree that we are finding incineration to be expensive, harder than you'd think, and it's unfortunate to not take advantage of the energy/nutrient value of poop. We are looking into incineration given the small quantity of poop and the cost of coordinating transport and reuse. Being poop from hospitals, there are some extra concerns about diseases too, so moving untreated poop offsite is a hurdle. Even burying untreated poop under a tree would need to be carefully considered to show it's safe.   

Thanks for the numbers Jeff, that's great to see. We'll keep biochar in mind. There could be some benefits to having a reuse product if we can find someone to take it and pyrolysis seems a bit easier and less energy-intensive than incineration.

Eil      
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  • Tore
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Re: Incineration of UDDT waste at healthcare facilities - request for feedback

You haveto remember that wet feces take a huge amount of energy to dry and subsequently burn.  If you can store the feces for a period of time in an enclosure where there is a glass window to the south it would heat the inside and help dry the feces.  Allowing some air to enter and installing a vent pipe to allow the water vapor to leave would help.  The dryer the feces the less energy to burn. 
Are you trying to use the urine for fertilizer or where does it go?

Tore
Sanitation & water consultant in developing countries
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