Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer?

  • Ronniedeb
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Re: Which composting toilet to choose - recommendations, please?

Hi Joe,

I think, if we are very technical, All dry toilet systems, of which there are many, facilitate composting to some degree. This does not always result in a beautiful, fully stabilised, sanitised "compost" except in the case of the very sophisticated BioR21 type, which carries-out 100% aerobic composting, but then also uses quite a lot of electricity.
I am personally involved in the sale, installation and maintenance of dry and composting toilets here in the west and I am in regular conversations with wastewater engineers and legislators on the merits of dry sanitation from an environmental, financial and health point of view, and in my opinion, the point is to compare like with like (regardless of composting performance):
1. Volume - keeping it dry reduces the volumes of waste by 100's of multiples

2. Introduction of air/oxygen - whether the composting is happening fast or slow, most human enteric pathogens come from an anaerobic environment in the body and tend to thrive in nutrient-rich water(I know...there are limitations to that statement) but are more likely to be deemed inactive once in an aerobic environment (once such an environment is maintained).

3. Solid waste and separated leachate/urine (whatever the system may be) are considerably less likely to transport pathogens and enrichment to any distance from the facility, E.G to ground water, surface water and the catchments connected to them.

When I design and build composting toilets I always incorporate a secondary treatment for both the solids and the liquids(which should always be separate) before land application. This could be a wood-chip composter for the liquids and a wormery for the solids or a serviceable transfer to a composting facility. In some cases, like in forestry or scrubland, it is possible to percolate leachate and Nitrified urine to the ground via the surface once good dispersal is observed, anyway you are talking relatively small quantities, even in busy public toilets.

To sum it up, I personally distance myself from the term "composting toilets" and rather use "dry toilets" or even "waterless toilets" but that is due to the bad reputation that poorly designed "composting toilet"systems had gotten over the years. The truth is that one way or the other, composting does take place and so the term is fair in my opinion.

See attachment below - pictures of BioR21 which we use and install, and is a true composting machine (you can hold the compost in your hands the next day)

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  • joeturner
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Re: Which composting toilet to choose - recommendations, please?

I'm not sure why you think I'm disagreeing with any of that.

If faeces composting does not consistently reach 55 degrees, secondary treatment is necessary.

Dry vaults below toilets might well have various advantages. But the one thing we can be sure about is that in places where pathogens are endemic (especially where healthcare is difficult), low temperature "composting" is not sufficient to kill pathogens.

Again, that might not matter if other barriers are in place - healthcare, education, regulations, inspections, secondary treatment, gloves, specialist skills etc.

But in the majority of places where "composting toilets" are being marketed, the barriers don't exist.
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  • muench
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Re: Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer?

Hi all,

It's been an interesting discussion so far. I am still keen to work on the definition issue a bit further and the best place to do that is on Wikipedia, I think. There is a separate thread for that here: forum.susana.org/discussions-about-speci...e-on-wikipedia#27525 . So anyone who wants to help spread useful, objective, verifiable information about composting toilets via Wikipedia please head over to that thread.

I also wanted to react to Geoff's statement:

Again, one key question that nobody has addressed:

Is Susana (and the forum) a popular public access forum for people to share their opinions, or does it have purpose / a mandate to protect public health and guide development with this as a guiding principle.

If the first (public open forum) this forum is well populated with full spectrum of opinions, people can read and make their own mind up.

If the second (with mandate to protect human health), someone needs to step in and help draw conclusions and make statements.

If the second, Susana needs to define what compost means to them, with regards to their mission and mandate. Is it the rotting of organic waste in a pile to make soil conditioner? Or is it an engineered process with controls and critical check points to be sure to minimize risk and provide high confidence to low-skill, minimal PPE wearing operators, and un-informed end-user (subsistence farmers).


Here I think we should distinguish between the SuSanA discussion forum and SuSanA as a network/platform/alliance.
The SuSanA discussion forum certainly fulfills the role that you have described in your first point. The purpose of the forum is:
"The Forum enables us to freely share knowledge and ideas about sustainable sanitation within the network and beyond.” If someone was spreading blatantly wrong misinformation or off-topic stuff then I'd step in as a moderator and it would most likely be deleted. But if people have different interpretations of the same data sets, different assessment of what is a high risk and what not, then we need to allow the discussion to take place and readers can draw their own conclusions.

Regarding your second point: SuSanA as a network/alliance/platform does not have a mandate to "endorse" or not endorse particular technologies. You will see in all of SuSanA's publications that we do not go down to that level of detail. The SuSanA publications remain rather higher level. See all SuSanA publications here in the library: www.susana.org/en/knowledge-hub/resource...5&vbl_2%5B%5D=&test= The publications talk about sustainable (and safe) sanitation as the aim, meeting SDG 6 but do not try to mandate which technology to use or not use. Yes, there has been a bit of an emphasis on safe reuse activities in the past as they can lead to a more sustainable system overall but if it's not safe then don't do it. And yes, UDDTs do feature in a lot of publications of our SuSanA partners as they have some advantages, particularly if water is scarce. But again, there is no SuSanA publication that would stipulate that UDDTs are the preferred technology choice in all circumstances.

Also, no SuSanA publication says that you should compromise on safety with regards to spreading something (treated human excreta) on vegetables that are to be eaten raw if it is not safe to do so.

I think Dean made a good point in his post from 16 July:

There also needs to be some context around what is "safe". Safe to be handled and spread around? Safe to put around food crops that will be eaten raw? Safe to sell as a product? These are all different, I'd be happy to spread compost full of helminths around some trees, I'd just wear gloves and maybe a dust mask to be safe. What I'm most interested in is a product safe to spread around in crops, but even this safety level varies according to whether the crop is to be cooked or eaten raw.


Regards,
Elisabeth

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Dr. Elisabeth von Muench
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  • geoffbhill
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Re: [SuSanA Forum] Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer? (Composting toilets, Arborloos)

Thanks, good comments.

However the question is not about "technogies" or "products" per se. Composting is a process that has key parts and biochemistry, and minus any of these, I am professing it not be called composting.

If a water treatment system advertised that it treated the water to make it safe, but in fact it just shone a green LED at the water as it passed through, would we allow it? Accept it? Would we allow it to be called "treatment" if we knew many many people were going to use it and even love it?

We are arguing about a word, a definition, similar to "treatment" for water, but for solid pathogen rich human waste. Composting does not happen under a toilet hole. We should not proliferate the term composting toilet.

Geoff Hill
Toilet Tech 206-966-6009
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  • AndyWarren
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Re: [SuSanA Forum] Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer? (Composting toilets, Arborloos)

I’ve been enjoying this discussion about what the word composting might mean and about the quality of the finished product. I can see the importance of refining the definitions of compost and perhaps there needs to be a new definition for compost which is fit for growing food. It would need to easily remembered, have some kind of official status and become widely recognised and used. Of course, compost of that standard could be arrived at through different technologies and so the definition should not refer to the method used but rather to the standard reached. I am almost certainly not the person to be coming up with a new definition but somebody probably can. (FFF Compost - Fit for Food; 3F Compost * ? !)

Many of NatSol’s toilets go on allotment sites in the UK and our instructions make it clear that the compost should not be used for growing crops on those sites even if composting is continued for several years after removal from the toilet vaults. I feel reasonably assured that people understand that, and in the UK there is neither a shortage of food (yet) nor a shortage of other sources of compost to assist in the growing of vegetables. Consequently, the pressure to use whatever is available is almost certainly low. In poorer countries without access to garden centres or stables for horse muck, and where food may be short then the pressure to use compost from toilets (whether properly degraded or not) may be high.

Are we missing something here? Most nutrients are in the urine. I’m sure that on some of the sites for which NatSol has supplied CTs the allotment association has planted soft fruit bushes over the urine soakaway in order to make use of this nutrient rich liquid, once known as household fertiliser. I do know that the Soil Association does not permit the use of urine for probably three reasons: 1. although generally regarded as sterile it may not be, especially (though not exclusively) because it may suffer contamination from faecal material in the urine separation system, 2. it does not add humus to the soil, 3. it can contain medications, including oestrogen from the contraceptive pill. Having said all that, it’s a damn sight safer than badly composted (non 3F) compost made from faeces.

This reminds me of the book ‘Future Fertility’ by John Beeby (1995) in which John makes the point that we are not short of nutrients from organic sources for growing food because there are a whole stack of these in urine, but we do need to find enough in the way of carbon sources to produce humus through composting the urine and carbon together.

The volume of well composted material from faeces is remarkably small - in comparison to the starting volume. I have noticed that in NatSol toilet vaults the volume roughly halves over a one year period in the UK climate and if left longer (and kept moist enough) it will probably halve again in the next two years. And it doesn’t stop there.

Probably the best urine to collect is male, partly because it is free of oestrogen, particularly because it can be collected by a urinal and is therefore not subject to faecal contamination. But then men often don’t want to walk any distance to pee in a urinal on a remote site, they just pee where they are! Maybe they would make the effort if the nutrient value was made clearer.
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  • kimgerly
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Re: Which composting toilet to choose - recommendations, please?

IWA Blue-Green Systems paper is available now.
IWA Blue-Green Systems | Compost Toilet System paper

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  • bowenarrow
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Re: Which composting toilet to choose - recommendations, please?

The Kailash Ecovillage experience is very encouraging. The experiment seems to be well designed, thought out, tested and reported in a manner that all can read and understand. A practical case study over a reasonable length of time, in terms of longevity and seasonal variance.
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  • geoffbhill
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Re: Which composting toilet to choose - recommendations, please?

Good article. This is not a composting toilet. Please correct me if I'm wrong, but this is batch composting human waste collected from urine diverting toilets. There is no dream of making compost in the collection bucket is there?

Geoff
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  • kimgerly
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Re: Which composting toilet to choose - recommendations, please?

Geoff. Thanks. Yes, you are correct on all your enquiries. To reiterate there is NO dream of making compost in the container/bucket. All the composting happens in the nine processor bins. See Figure 2F, which is the compost processor.

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  • joeturner
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Re: [SuSanA Forum] Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer? (Composting toilets, Arborloos)

AndyWarren wrote:
Are we missing something here? Most nutrients are in the urine. I’m sure that on some of the sites for which NatSol has supplied CTs the allotment association has planted soft fruit bushes over the urine soakaway in order to make use of this nutrient rich liquid, once known as household fertiliser.


Well, urine is certainly high in urea - which is a good source of nitrogen. The trouble is that it isn't correspondingly balanced in Potassium and Phosphate, so is unlikely to meet the needs of many crops on its own. Faeces is much more balanced in terms of NP and K.

Hence most many farmers spread farmyard manure (a mix of bedding straw, faeces and urine) rather than neat urine.

I highly doubt that most British allotments are limited by nitrogen.

I do know that the Soil Association does not permit the use of urine for probably three reasons: 1. although generally regarded as sterile it may not be, especially (though not exclusively) because it may suffer contamination from faecal material in the urine separation system, 2. it does not add humus to the soil, 3. it can contain medications, including oestrogen from the contraceptive pill. Having said all that, it’s a damn sight safer than badly composted (non 3F) compost made from faeces.


This is quite a tangent to the discussion, but I doubt that the Soil Association (which is one of the group's promoting 'organic' food - also known as 'ecological' food in other countries) was/is worried about any of those things. But let's talk about that on a different thread, it has nothing much to do with this.

This reminds me of the book ‘Future Fertility’ by John Beeby (1995) in which John makes the point that we are not short of nutrients from organic sources for growing food because there are a whole stack of these in urine, but we do need to find enough in the way of carbon sources to produce humus through composting the urine and carbon together.


Finding sufficient carbon sources for efficient composting and to achieve high temperatures is often a major problem. The other part of the quote does not really make a lot of sense.

The volume of well composted material from faeces is remarkably small - in comparison to the starting volume. I have noticed that in NatSol toilet vaults the volume roughly halves over a one year period in the UK climate and if left longer (and kept moist enough) it will probably halve again in the next two years. And it doesn’t stop there.


Yes. Faeces in toilet vaults often reduces in volume. That doesn't mean it is composting, of course.

Probably the best urine to collect is male, partly because it is free of oestrogen, particularly because it can be collected by a urinal and is therefore not subject to faecal contamination.


I highly doubt this is true. Given that the vast majority of farmed ruminent manure and urine is from females, and the majority of that is spread on fields, I suspect any problems with oestrogen would have been noticed.

But then men often don’t want to walk any distance to pee in a urinal on a remote site, they just pee where they are! Maybe they would make the effort if the nutrient value was made clearer.


I honestly don't know what this means. You have allotment toilets where the urine soaks away, some of which may be used by fruit trees. Are you seriously trying to suggest that it would be sensible to separate urine from men and women?
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  • joeturner
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Re: [SuSanA Forum] Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer? (Composting toilets, Arborloos)

To clarify: oestrogen in urine causes problems in water. I don't think it is believed it causes problems in soil.
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  • AndyWarren
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Re: [SuSanA Forum] Composting toilets do not produce compost - true or false? And is "composting toilet" a misnomer? (Composting toilets, Arborloos)

A quick response to Joe Turner’s post on 11 August 19. I do realise that in straying into the area of ‘piss’ and its nutrient value I have gone rather off-piste. However, I will give some short answers, after which I’ll desist, at least in the context of this thread.

I understand urine is typically 88% N; 67% P; and 73% K. I got those figures from: Characteristics of urine, Faeces and Grey Water by Elisabeth Muench. That’s not such a bad balance. If I ‘normalise’ those numbers by treating the N as 100% then the P and K are respectively 76% and 83%. Dilution of urine (say 10:1 water to urine) is important mainly to avoid high levels of Sodium and Chlorine ions.

A NatSol client involved in certified organic production asked the Soil Association (SA) if they could use urine as a fertiliser. The answer was 'no' and I’m sure that two of the reasons were reasons that I have given, i.e. the risk of faecal contmanination and the fact that it does not add humus (unless composted of course). However, you are probably right, Joe, in saying that oestrogen isn’t a problem in soils, only in watercourses.

Given the concern that the SA has about the risk of faecal contamination (e.g. in urine separating pedestals) there could be some good reasons for handling male and female urine separately. In NatSol toilets the male urine almost all goes down a urinal and although this usually combines with female urine from the pedestal it would be a very simple matter to keep it separate. That would keep it free of faecal contamination.
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