Dear Toni,

I have now worded the information about odorous gases from composting toilets like this:

en.wikipedia.org/wiki/Composting_toilet#Odorous_gases

Odorous gases
The following gases might be emitted from the composting processes which take place in composting toilets: hydrogen sulfide (H2S), ammonia, nitrous oxide (N2O) and volatile organic compounds (VOCs).[4] These gases can potentially lead to odour nuisance. Some methane may also be present but it is not odorous.

Reference 4 is your publication from 2011 entitled "Detection, Composition and Treatment of Volatile Organic Compounds from Waste Treatment Plants" which could be used to back this up, right?

By the way, if you are an odor expert, could you provide some comments on this odor research project by Duke University?:
forum.susana.org/forum/categories/105-pr...colorado-boulder-usa

I would be curious to hear your thoughts about that project (in that other thread).

They also ran an odor survey, see here:
forum.susana.org/forum/categories/105-pr...iversities-in-the-us

Regards,
Elisabeth

Note by moderator: this post is the answer to a post by Elisabeth von Muench on 7 April (see on page 2 of this thread above):

+++++++++++

About URLs, unfortunately, most of them are copyright protected by the publishers, so they are not open access. The abstract can be consulted in the webpage of the journal, as I have indicated. One of them is open access (I have added the URL*).

About the Wikipedia sentence (en.wikipedia.org/wiki/Composting_toilet#Components):

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)

, it is right, but I would also add a family of not so well-known gases, which have some importance, being detected in any composting process:

N2O: a powerful GHG (298 times more impact per unit mass of CO2).
VOCs: a large family of organic volatile compounds which are just being identified, some of them with hazardous characteristics.

Regards,
Toni

* This one is open access:
Detection, Composition and Treatment of Volatile Organic Compounds from waste treatment plants. Font, X., Artola, A., Sánchez, A. Sensors. 11, 4, 4043-4059 (2011).
www.mdpi.com/1424-8220/11/4/4043

See also the book chapter that I mentioned here on "Greenhouse Gas from Organic Waste Composting: Emissions and Measurement":
forum.susana.org/forum/categories/70-com...nd-measurement#14585

Thank you, Joe, for your enlightened response. I reckon, there will be then few cases of truly aerobic composting systems.

And, in case, anaerobic process creeps in, we can use adsorption, absorption or scrubbing, thermal oxidation and biological treatment for the removal of VOCs and other gases, in the emissions.

F H Mughal

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.

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.

F H Mughal

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.

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?

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.

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:

• This present one called (i.e. the thread that you are reading right now): What do we know about odorous gases from composting toilets (or from composting in general)?
• A new thread called: How should we call the excreta-derived product of a composting toilet? Do we need a new term? (forum.susana.org/forum/categories/70-com...o-we-need-a-new-term)
• A new thread called: How aerobic are composting toilets really? How much pathogen kill? Clivus Multrum? And comparison with UDDTs (forum.susana.org/forum/categories/70-com...omparison-with-uddts)

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

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

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.

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.