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

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

I suppose I can believe the reports that faeces in small boxes are composting - but it does seem to me to stretch credibility and logic.

Personally the only system I'd have confidence was actually composting would be a regularly turned windrow - and even there I believe there is evidence that areas which have not reached temperature can re-inoculate areas which have.

The reason is that I believe you need the volume and correct C:N ratio to reliably get to high temperatures needed to kill pathogens - plus sufficient oxygen to allow aerobic microbial respiration. I think there is good evidence to show this in the academic literature and only anecdotal evidence supporting the idea that small, enclosed,composting toilets actually do any kind of treatment n a reproducible and reliable way.

But changing anything seems like a monumental task given how many are distributing these kinds of system.
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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)

Great work! (note by moderator: Geoff is referring here to this system in Portland, Oregon: forum.susana.org/98-resource-recovery-fr...-portland-oregon-usa )

This is composting in a batch process using human waste as a feedstock. This type of batch process and attention to mix can reliably achieve thermophilic temperatures.

Bucket collection of human waste is not a composting toilet.

Batch Composting is being done (process) to human waste collected dry (no flush water) and transferred elsewhere for separate processing. This is not a composting toilet. In other words the batch composting of toilet waste is not a composting toilet. I blame long term poor use of this term on the misunderstandings that abound.

Geoff Hill
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  • KaiMikkel
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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 agree with Geoff, let's dispense with the term "composting" toilet and instead use, as applicable, "flush" and "dry". Maintaining use of the phrase "composting toilet" is irresponsible and, as Geoff has rightly pointed out, so obviously flies in the face of the core tenets of SUSANA and its pursuit of improved public health.

Kai Mikkel Førlie

Founding Member of Water-Wise Vermont (formerly Vermonters Against Toxic Sludge)
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  • goeco
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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)

Hot composting has so many variables that influence the outcome... the volume, the c:n ratio, oxygen levels, moisture levels, ambient temperature, heat exchange... in particular oxygen levels over time because these require replenishing, usually achieved through mechanical means. The interaction between variables, particularly volume and oxygen levels would be inherently difficult to consistently reproduce. I'd suggest that sample size would need to be very large to "prove" that a specific method of hot composting "works".

But in the end it is resulting pathogen levels that matter, the outcome not the process. The one tried and true method for destroying pathogens involves the variable time. High temperature is not required to destroy pathogens, provided you're willing to wait. The difference is that time is 100% reliable. The other variables don't really matter when time is involved.

In order to make compost there needs to be a thermophilic stage.


Not true.

Compost is better defined as the product, i.e. "safe, stable, mature" rather than any specific biological process to achieve that. If I make a toilet that does not involve a thermophilic stage, but I design it so the decomposed waste rests for 2+ years before being handled, why shouldn't I call it a composting toilet?

I would suggest that Elisabeth updates her definition to:

A composting toilet is a type of toilet that treats human excreta by a biological process called composting. This process leads to the decomposition of organic matter and turns human excreta into humus-like material, but may not destroy all pathogens. A pathogen-removing composting toilet includes processes that destroy all pathogens.


If there isn't decomposition then it isn't a composting toilet. Dehydrating human excreta doesn't involve decomposition and the result isn't a humus-like end product.

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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)

High temperatures absolutely is required to kill some of the worst faecal pathogens in a faecal composting system.

Other effective systems exist. But "composting" at low temperatures with storage isn't one of them.
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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)

The US Composting Council (USCC) recently updated the definition of Compost to include the thermophilic process. They did this to protect public health from various compost producers who were negligent in adhering to pathogen reduction processes yet still able to market their (questionable) material as compost. Thank you to Ron Alexander.

wasteadvantagemag.com/uscc-efforts-resul...by-regulators-group/

Pathogen destruction through time is highly dependent on site, moisture, pH, and temperature. Time to destroy ascaris ova can be multiple years. This is not a reliable method. Most composting toilets are operated as continuous flow. Material added to top seeps down to bottom (oldest material) with urine / drainage. So time is not really achieved even here.

If material is pulled out to batch treat by "time" the operator might as well do a "Jenkins" batch compost process by adding bulking agent. Heat destroys pathogens many orders of magnitude faster than "time" treatment.

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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 agree though that anyone is free to call their system a "composting toilet" if they want to ignore all the recent studies in the scientific literature and redefine terms.

I'd argue that if we know that these systems do not reliably destroy pathogens, they can't honestly be described as "sustainable sanitation".
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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)

Hi Joe, the scientific literature is very clear that pathogen levels reduce over time in decomposed human excreta.
Even the most robust of these, helminth ova, are all gone in two to three years. Pathogens are reliably destroyed with decomposition followed by storage.
cheers
Dean

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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)

2-3 years time is not a reliable mechanism in a working toilet at a refugee camp. Think real world applications. Doesn't get around the issues with short circuiting.

Fascinating that people are so strangely emotionally attached to the term "composting" toilet. Worthy of psych study.

Geoff Hill
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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)

Ok Dean - show me a study where faeces "composted" at less than 50 degrees followed by two years of storage killed off all helminths.
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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)

There have been a lot of studies published in the literature in the last 18 months looking at pathogen survival in composting toilet systems. Enough that I think we may need to conduct a widespread review of the Wikipedia page to take account of them - some including risk (using Monte Carlo systems) DALYs of handling and using the materials etc.

I can't find anything suggesting that Helminths are completely destroyed after even 2 years of post-treatment storage, even when that treatment is in a fully managed facility never mind a composting toilet system.

I will keep looking.
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  • goeco
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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)

Hi Geoff,
Commercially produced compost should clearly meet standards for pathogen levels to protect the consumer. This is irrelevant to compost from toilets, unless that compost were to be sold.

Pathogen destruction through time is highly dependent on site, moisture, pH, and temperature.


"highly dependent" is perhaps an exaggeration. Dependant yes, but decomposed human excreta (compost), held for a specified period of time within a reasonable range of moisture levels and temperatures is universally achievable. Perhaps Alaska would need longer than Florida, but my point is that I'm a lot more comfortable with compost that has rested for a conservative time period such as 5 years, than with a Jenkins batch-produced compost because I simply cannot be assured that the variables were adequately controlled for consistent heat right through for the required period of time.

We all know a continuous flow system can't rest and I'm not suggesting any period of rest is achieved with such a system. In contrast, twin batch systems just need to achieve whatever time period is required before switching over. Whether that time period is deemed to be two years or five years is just a design/capacity issue.

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