What do we know about odorous gases from composting toilets (or from composting in general)?

  • DaveBates
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

H2S AND SULFURIC ACID ????
Back in the 1980's in our early years, once a user of a UDDT (aka "composting toilet") reported that the underside of his leg was being "burned" evidenced by a rash on the underside of his leg that he believed was a result of sitting on the seat of his UDDT. It was investigated, and believed that hydrogen sulfide may have been being released, mixing with humidity in the chamber, converted to sulfuric acid (H2SO4), and precipitated out on the seat. We added ventilation to that toilet, and more or less, insisted that future models, include the vent pipe, whether the person/program believed the vaults produced "offensive odors" or not. For that particular home, we designed & built a toilet seat with a special toilet lid (with a fabric as part of the lid) that allowed the toilet to "breathe" and expel more gas through the seat, in case the vent pipe was not achieving adequate ventilation. Whether H2S was being produced or not, depends of course on what type of process (aerobic vs. anaerobic) is going on in the toilet and different parts of the pile at the time; this can change of course over time, with amount of lime added, if urine is introduced accidentally, level of moisture in the pile, that can be affected by the season and weather.
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  • arno
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

DrBates:
Sounds more like a sealed potty with air-tight cover and no air inlet thus producing hydrogen sulfide. That's not a UDDT. Sounds more like an evil experiment.

Regarding the formation of sulfuric acid from hydrogen sulfide, this doesn't normally occur in nature. The H2S can dissolve in water and produce a mild acid but it is nothing at all like H2SO4. To produce sulfuric acid requires an oxidative process from sulfur dioxide, not the conditions of that "toilet". H2S toxicity could explain the skin irritation. This is a noxious and highly toxic substance. www.alken-murray.com/H2SREM9.HTM

But the good thing about H2S is that is is easily detectable because it smells so bad. No one with any normal level of olfactory capacity would want to come anywhere near such a "toilet".

Good you added the ventilation which also enhances drying. And you got your PhD to boot!
--Arno

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  • DaveBates
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

I have seen a WIDE variety of toilets, over 20 years in the field supporting, building, and assisting with maintaining them, alot of UDTs,seeing them 10-20 years after initial construction & start up. Some poorly operated ones ARE indeed really bad.... Some we come across are abandoned permanently and we sample them to observe and learn from all cases....Many don't admit to the "dark side" of poor UDT applications....they exists and they are point sources of contamination. Some lay out of operation, then restarted when migrating family comes home or someone buys home with toilet built by other....I remember this particular toilet - it was sealed up really tight, this village was very humid, and it did smell really bad....I too doubted that it could be full blown H2SO4, and appreciate your clarification that it could have been a mild acid...any details you have to share on "chemically" what the acid would look like, I would be interested in seeing it...always like to learn. By the way, I don't assume anything when it comes to sealing human waste up tight in vaults....I have seen everything from extremely desiccated dust as an end product, to a wet mess in vaults due to visiting individuals urinating in the vaults during a party. I respected the observation made by the Mexican technician and remained open to his observation since the vault was one of those extreme cases. Thanks for the feedback
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

David
The hydrogen sulfide is as far as I understand dissolved in water. It can be removed by aeration. This is the common method of scrubbing H2S from biogas before use.

Yes things have changed in Vietnam. A month ago when visiting some villages near rice paddies 2-3 hours from Hanoi, we were informed that ecosan toilets were now thought to be primitive and are no longer promoted. Pour flush with septic tanks was the preferred method (also since there were subsidies involved). The explanation for the shift from ecosan was that they had shifted to bottled propane for cooking, no longer burning biomass in smokey kitchens. This meant that there was no longer wood ash for the ecosan toilets. So modernising cooking has led to different attitudes around toilets. The brick septic tanks were however difficult to accept seeing that they were being installed only a few meters from fish ponds and rice paddies, with their porous base submerged below the water line.

The example shown of the primitive ecosan toilet was an older blind woman who was using rice husk ash to cover the faeces in her simple ecosan squating place (no vault, just two bricks to squat on just above the ground). The urine was infiltrating and had produced over the years a grove of large banana plants.

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  • tonacho
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

We know a lot really, our group has extensively worked on this topic, for instance:

Odours and volatile organic compounds emitted from municipal solid waste at different stage of decomposition and relationship with biological stability. Scaglia, B., Orzi, V., Artola, A., Font, X., Davoli, E., Sánchez, A., Adani, F. Bioresource Technology. 102, 7, 4638-4645 (2011).

Detection, Composition and Treatment of Volatile Organic Compounds from waste treatment plants. Font, X., Artola, A., Sánchez, A. Sensors. 11, 4, 4043-4059 (2011).

Determination of the energy and environmental burdens associated to the biological treatment of source-separated Municipal Solid Wastes. Colón, J., Cadena, E., Pognani, M, Barrena, R., Sánchez, A., Font, X., Artola, A. Energy & Environmental Science. 5, 2, 5731-5741 (2012).

GHG contribution of sorting plants and mechanical biological treatment plants - Case study of Catalonia, Spain. Villalba, G., Bueno, S., Gabarrell, X., Font, X. Waste Management. 32, 10, 1999-2002 (2012).

Home and vermicomposting as sustainable options for biowaste management. Lleó, T., Albacete, E., Barrena, R., Font, X., Artola, A., Sánchez, A. Journal of Cleaner Production. 47, 70-76 (2013).

VOC emissions from the composting of the organic fraction of municipal solid waste using standard and advanced aeration strategies. Maulini-Duran, C., Puyuelo, B., Artola, A., Font, X., Sánchez, A., Gea, T. Journal of Chemical Technology & Biotechnology. 89, 579-586 (2013).

A systematic study of the gaseous emissions from biosolids composting: raw sludge versus anaerobically digested sludge. Maulini-Duran, Artola, A., Font, X., Sánchez, A. Bioresource Technology. 147, 43-51 (2013).

GHG emissions during the high-rate production of compost using standard and advanced aeration strategies. Puyuelo, B., Gea, T., Sánchez, A. Chemosphere. 109, 64-70 (2014).

Environmental assessment of two home composts with high and low gaseous emissions of the composting process. Quirós, R., Villalba, G., Muñoz, P., Colón, J., Font, X., Gabarrell, X. Resources, Conservation and Recycling. 90, 9-20 (2014).

Gaseous emissions in municipal wastes composting: effect of the bulking agent.
Maulini-Duran, C., Font, X., Artola, A. Sánchez, A.
Bioresource Technology. 172, 260-268 (2014).

Gaseous emissions during the solid state fermentation of different wastes for enzyme production at pilot scale. Maulini-Duran, C., Abraham, J., Rodríguez-Pérez, S., Cerda, A., Jiménez-Peñalver, P., Gea, T., Barrena, R., Artola, A., Font, X., Sánchez, A.
Bioresource Technology. Accepted.

Greenhouse gas (GHG) emissions from organic waste composting. Sánchez, A. Artola, A, Font, X., Gea, T., Barrena, R., Gabriel, D., Sánchez-Monedero, M.A., Roig, A.,, Cayuela, M.L., Mondini, C.
In: Lichtfouse, E., Schwarzbauer, J., Robert, D. Environmental Chemistry for a Sustainable World (Vol. 5, CO2 Sequestration, Biofuels and Depollution, pp 33-70).
Springer (2015).
ISBN 978-3-319-11905-2.

Antoni Sánchez Ferrer (male, PhD) is Full Professor in the Department of Chemical Engineering at the Universitat Autònoma of Barcelona. His main research activities have been focused on biological waste treatment, especially on composting processes.

scholar.google.es/citations?user=f2hh0z8AAAAJ&hl=ca
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  • muench
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

Dear Toni,

Thanks for providing this list of your publications in relation to odour from various sanitation systems. To make it easier for people who do not have direct access to university servers and libraries, could you please provide the URLs for those publications that are freely accessible? Are any of them free access or even open access? If yes, it would make it easier for me to include information in the Wikipedia article on composting toilets.

From your perspective and your research, is there particular information that should be added to this Wikipedia article to clarify issues around odorous gases from composting toilets?
en.wikipedia.org/wiki/Composting_toilet

Or perhaps more appropriately, which information should be added to the Wikipedia article on composting in general?
en.wikipedia.org/wiki/Compost

As was mentioned by a few people in this thread, the issues around odour and the chemistry involved are still quite poorly understood. Getting the information into easily understandable language on Wikipedia might help us all.

To all:

I have in the meantime changed that bullet point in the Wikipedia article about composting toilets ( en.wikipedia.org/wiki/Composting_toilet ) (see my first post in this thread to check how it was originally) to:

a ventilation unit to ensure that the degradation process in the toilet is predominantly aerobic and to vent odorous gases, such as hydrogen sulfide and ammonia (some methane may also be present but is not odorous)

Good like this?

Regards,
Elisabeth

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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

Dear all,

Thank you to everyone who has contributed to this thread so far! In my role as moderator, I have now split off two sub-threads as the discussions were dealing with different topics. I hope the split that I have done is quite clear. We now have three threads from what used to be just one thread:
I hope you find this new arrangement useful.
I think initially it is OK to let it all flow in one thread but at a certain point in time, splitting into sub-threads is better to keep the different discussions focussed and to also allow new people to join in.

If you have suggestions for different thread titles or other ways of arranging this, please contact me directly (e-mail address given below, or message function to the left of this post).

Regards,
Elisabeth

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  • tonacho
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

We know a lot really, our group has extensively worked on this topic, for instance:

Detection, Composition and Treatment of Volatile Organic Compounds from waste treatment plants. Font, X., Artola, A., Sánchez, A. Sensors. 11, 4, 4043-4059 (2011).

(open access: www.mdpi.com/1424-8220/11/4/4043 )

Other papers available in the journal website (only Abstract):

Odours and volatile organic compounds emitted from municipal solid waste at different stage of decomposition and relationship with biological stability. Scaglia, B., Orzi, V., Artola, A., Font, X., Davoli, E., Sánchez, A., Adani, F. Bioresource Technology. 102, 7, 4638-4645 (2011).

Determination of the energy and environmental burdens associated to the biological treatment of source-separated Municipal Solid Wastes. Colón, J., Cadena, E., Pognani, M, Barrena, R., Sánchez, A., Font, X., Artola, A. Energy & Environmental Science. 5, 2, 5731-5741 (2012).

GHG contribution of sorting plants and mechanical biological treatment plants - Case study of Catalonia, Spain. Villalba, G., Bueno, S., Gabarrell, X., Font, X. Waste Management. 32, 10, 1999-2002 (2012).

Home and vermicomposting as sustainable options for biowaste management. Lleó, T., Albacete, E., Barrena, R., Font, X., Artola, A., Sánchez, A. Journal of Cleaner Production. 47, 70-76 (2013).

VOC emissions from the composting of the organic fraction of municipal solid waste using standard and advanced aeration strategies. Maulini-Duran, C., Puyuelo, B., Artola, A., Font, X., Sánchez, A., Gea, T. Journal of Chemical Technology & Biotechnology. 89, 579-586 (2013).

A systematic study of the gaseous emissions from biosolids composting: raw sludge versus anaerobically digested sludge. Maulini-Duran, Artola, A., Font, X., Sánchez, A. Bioresource Technology. 147, 43-51 (2013).

GHG emissions during the high-rate production of compost using standard and advanced aeration strategies. Puyuelo, B., Gea, T., Sánchez, A. Chemosphere. 109, 64-70 (2014).

Environmental assessment of two home composts with high and low gaseous emissions of the composting process. Quirós, R., Villalba, G., Muñoz, P., Colón, J., Font, X., Gabarrell, X. Resources, Conservation and Recycling. 90, 9-20 (2014).

Gaseous emissions in municipal wastes composting: effect of the bulking agent.
Maulini-Duran, C., Font, X., Artola, A. Sánchez, A.
Bioresource Technology. 172, 260-268 (2014).

Gaseous emissions during the solid state fermentation of different wastes for enzyme production at pilot scale. Maulini-Duran, C., Abraham, J., Rodríguez-Pérez, S., Cerda, A., Jiménez-Peñalver, P., Gea, T., Barrena, R., Artola, A., Font, X., Sánchez, A.
Bioresource Technology. Accepted.

Greenhouse gas (GHG) emissions from organic waste composting. Sánchez, A. Artola, A, Font, X., Gea, T., Barrena, R., Gabriel, D., Sánchez-Monedero, M.A., Roig, A.,, Cayuela, M.L., Mondini, C.
In: Lichtfouse, E., Schwarzbauer, J., Robert, D. Environmental Chemistry for a Sustainable World (Vol. 5, CO2 Sequestration, Biofuels and Depollution, pp 33-70).
Springer (2015).
ISBN 978-3-319-11905-2.

Antoni Sánchez Ferrer (male, PhD) is Full Professor in the Department of Chemical Engineering at the Universitat Autònoma of Barcelona. His main research activities have been focused on biological waste treatment, especially on composting processes.

scholar.google.es/citations?user=f2hh0z8AAAAJ&hl=ca
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  • ddiba
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

Hi everyone.

Like Chris above, I have also found quite a huge gap in available literature on the exact quantities of emissions from various toilet technologies (or I haven't searched quite thoroughly enough).

Apart from the thesis by Pui Ki which Elizabeth mentioned above, I have come across another post by Alison Parker about a project they were doing at Cranfield to quantify emissions from different sanitation systems but the results haven't been published as much as I know.

Does anyone know of any studies that address this question?

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  • bones
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

In my understanding of composting, which has been stated, is an aerobic process, if H2S is being produced, then the pile (or toilet) has become (at least in part) anaerobic.

In the context of a toilet, do we consider that this is unavoidable, or should we be mentioning that in this case, the operation and maintenance of the toilet needs to be reviewed to ensure it can work properly.

If it is not unavoidable, then why do we call these things composting toilets - if in fact the cannot compost (which is an aerobic process).

Or are we completely missing the point in this discussion, that the odours which are generally produced, are not H2S, or NH3 - they are the smell of faeces.
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  • F H Mughal
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

I'm a bit confused on this. Composting is an aerobic process. The by-products, therefore, should be CO2 and H2O. If H2S and NH3 are produced, then, something is not quite right, as these are the by-products of an anaerobic process.

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  • joeturner
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Re: What do we know about odorous gases from composting toilets (or from composting in general)?

The process is aerobic, but the conditions may limit the amount of oxygen in the material. This will lead to pockets of anaerobic conditions within the material, anaerobic breakdown and the release of the odorous gases. The only way this could be prevented would be to force air through it or to mix the material regularly.

The thing that is "going wrong" is therefore that there is not enough oxygen getting to all of the material as it is breaking down. The smaller the container and/or the poorer the airflow, the more likely there will be anaerobic pockets in the compost. As I said previously, this happens with all composts.
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