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

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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 WHO guidelines for the safe use of wastewater, excreta and greywater Vol 4 part 1 table 3 gives die-off of Ascaris (90% inactivation) as 125 days +- 30 days for faeces and 625 +-150 days for soil. I suggested 2-3 years which isn't far off what is published for soil.

Ascaris was the slowest to die off, followed by Cryptosporidium then Giardia. The point I am making is that pathogens die over time, and whether that time is two years or five years, this should be acknowledged.

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Dean

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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)

Well let's see about this.

First the WHO standards are not "recent literature" given that it was published in 2006 and we are now in 2019 - with recent studies of the actual system you are describing rather than generalities based on very old studies.

Second of all, table 3.9 of the WHO standard, page 45 gives an absolute maximum of 7 years in soil. Apparently based on a study from 1983.

Table 3.5 does indeed give a duration for survival on page 38 based on a study from 1994. But the text immediately below that table suggests that the "storage conditions will affect die off rates" and that one study from Denmark showed unacceptable risk even after 12 months and another from El Salvador showed Ascaris survival of 600 days in a latrine with a pH of 9.

Is 90% die off of Ascaris loading in faeces (in places where it is common and endemic) safe? Have you conducted Quantitative Microbiological Risk Assessment to find out?

The only way to be sure that Ascaris - and other pathogens - have been destroyed is with a reliable way to get the totality of the faeces to a high temperature.
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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)

What confuses me is why anyone would want to continue with a low temperature "composting" system that everyone here seems to be in agreement does not kill pathogens sufficiently.

What is so hard about designing systems that a) remove excess liquid b) ensure the material is mixed and aerated c) has sufficient carbon so that d) temperatures of over 55 degrees are reached for the (relative short) period to kill pathogens.

As I said above, it isn't really difficult to do in a windrow. One would think it isn't particularly difficult to design something with augers and stirrers and air pumps in more enclosed spaces - although I am not an engineer and couldn't do it. Personally I would always go for meso-scale outdoor composting sites.

So why persist with the fiction that one can add small/random amounts of carbon in a space with limited air and with much of the faeces sitting in a pool of water or urine - and produce compost that is safe to be handled and spread around?

It isn't that difficult to understand, is it? It is just a microbiological system like making cheese or beer - misunderstand the process or get a parameter wrong and the result will not be acceptable. And if you can't be sure that the process has been done correctly, then you can't assume that the product is safe.

Isn't that obvious? What am I missing?
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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 Joe,
Certainly we could debate what time period should be deemed safe, but what is not in question is that time does kill off pathogens.

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.

Lets consider low temperature composting in the most primitive of "compost toilet" systems, the twin pit, where decomposition occurs and capacity is sufficient for an agreed (based on science) safe resting period. After which period, the compost is deemed safe to handle and spread around the carrot crop. The product coming from this system is in stark contrast to sludge from a single pit, where pathogens are not killed because decomposition doesn't take place, or faeces sitting in a pool of water or urine without decomposing. Or ecosan compost after 6 months rest (the helminths are still all there), or even dried faeces where pathogens are simply re-activated when moisture is reintroduced.

Risk is never completely removed, whether hot or low temperature composted...

get a parameter wrong and the result will not be acceptable

Both have parameters that if not met (e.g. human error) increase the safety risk. I'm more comfortable with time than temperature, even if I have to wait 5 years for assurance, because

you can't be sure that the (hot composting) process has been done correctly

cheers
Dean

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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)

Dean - most of these points are not really points and have already been established.

Risk is estimated by considering Quantitative Microbiological Risk Assessment (QMRA) and is assessed against standards for acceptable numbers of Ascaris infections.

I invite you to look at the papers I added today to the thread called "Knowledge, attitudes and practices on use of Fossa Alternas and double vault urine diverting dry (DVUDD) latrines in Malawi" here where all of these are discussed in great detail.

In brief, 1 year of storage of these facilities in Malawi was not sufficient to get to safe levels. And there was no measured difference between the ecosan (whether or not one considers them to be "composting toilets" is an open question, perhaps) and other latrines.

There is no guarantee that storage will reduce pathogens to safe levels - whereas if all of the material reaches high temperatures they will be destroyed. Because basic microbiology.

Telling people that faeces from "composting toilets" are somehow safe to handle after six months, one year or even two years flies in the face of the available information.

And we don't know what could theoretically happen after five years. Which is an impossible scenario that is never going to happen anyway.
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  • bowenarrow
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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)

This debate should be measured by the time eternal question. "What are the alternatives ? " There certainly are alternatives but often you need to take into account the cost factor. If the more comprehensive systems are not affordable then we are faced with the worst scenario-
no system at all.
I started building Composting Toilet Systems in 1979 and to date I have only ever had one call out to a system that wasn't functioning. It wasn't mine, but it alerted me to problems associated with mixing urine with faeces and this prompted me to market only urine diverting pedestals.
Most people I deal with use the Pedestals for collection only with the partially composted material stored separately and interned to gardens when considered (unmeasured) to be appropriate. These people are not concerned with pathogen levels as they are dealing with their own family members and some even use the composted material for vegetables. I say composted because it is broken down, does not have odours and is easily spread. Compare this to a flushing district sewer main and the resultant effluent into the Ocean. My local sewer plant uses reverse osmosis and still there is a sludge on our beaches nearest the outfall. They say this is state of the art.
I would like to see more time putting a positive spin on this, rather than heaping criticism on what I consider a suitable and often necessary alternative, regardless of the semantics of appropriate titles.
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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)

Again, maybe you have managed to find a magic "sweet spot" whereby systems that should not logically work somehow do.

I think more likely you operate somewhere that a) does not have endemic nasty pathogens b) has easily accessible multiple barriers including gloves, good healthcare and clean water to wash hands.

The question is then not really about what you call your system - lots of clever names have been suggested - but that systems are taken to be working in "optimum" conditions and then applied to areas where none of the barriers exist. Where the consequences of unmeasured application to vegetables can be much more serious.

Personally I can see no reason to do that anywhere. The gains in terms of the nutrients from the faeces are much lower than the potential costs in terms of infection.
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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)

Joe, actually the EcoSan toilets in that paper were rested for only 6 months.

After using the latrine for defecation for 6 months or more, the latrine pit or vault is sealed for another 6 months to allow the pathogens to be killed.


Not surprisingly the results showed this not to be the case, but those results don't take us forward in any way:

More research is required to check if the helminths identified in EcoSan latrines are deactivated after the 6 months treatment period.


So who came up with the notion that Ascaris would be killed from 6 months slow composting? Seems bizarre to me that despite academic literature and WHO guidelines that this was promoted from 2001 till now.

OMG... reading the Malawi paper it gets even worse...

EcoSan latrines owners, where they were found to store their harvested sludge behind their households on bare ground. This led to uncontrolled spreading of manure around the household environment increasing the chances of infection


The WHO guidelines report a normal maximum survival in soil of 2 years for Ascaris (table 3.9). If there is still inadequate research results available now in 2019 to satisfy us then this community has real problems. Problems with academics not knowing what to research, problems with even knowing what conditions induce absolute maximum survival, resulting in an ignorance that allows some practitioners to recommend 6 months resting for EcoSan... Ignorance among sanitation experts who use confirmation bias to justify their position because the work has not been done to objectively quantify the time it takes for die off?

I will repeat myself. Pathogens reduce over time in compost. The scientific literature is very clear that pathogen levels reduce over time in decomposed human excreta.

If I am wrong, or the academics have not yet settled on time periods adequate for producing safe product, then the simple conservative approach is just to extend the period until we have settled it. I'm happy with 2-3 years after decomposition has occurred, but would be willing to design my systems to have 3, 4 or 5 years rest. Joe, you might want to believe that this

is an impossible scenario that is never going to happen anyway

but I disagree. Even twin pits can be designed to rest for that period.

Bill Gates is investing millions of dollars into sanitation, yet we, the sanitation community, apparently don't even know how long compost (decomposed faeces) need to rest before being safe to handle or use in crops? Wow, no wonder ascaris are rampant in Malawi and all those other counties that are relying on the international advisors and academics for sanitation solutions. Yet in 2019 we still don't know how long an EcoSan compost should rest for, despite that system being available for 18 years?

Wow.

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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)

Yeah ok Dean. They were tested after 1 year of storage. Do come back to discuss further after you've actually read all three papers.

And it is quite insulting to say things about academics who are taking measurements to test things that you say are happening based only on assertion.

You've no idea what's happening. How could you - you haven't tested anything.
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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)

Question by me in my moderator role: I have the feeling that the last few posts have focused on a slightly different topic than what the thread title suggests. What do you think, should I split them off into a separate dedicated thread with a new title (with adding links in both directions)? Or should they stay here?

And I can see a bit of tension building. Please everyone try to remain cool, calm and collected (and friendly) towards each other even if opinions may clash. We want this forum to be a friendly space. Thanks. :-)

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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)

Joe, I acknowledge that one study looked at 6 months and the other study looked at 12 months. However, neither of these provide useful data on how long an EcoSan compost should rest for, despite that system being available for 18 years.

Some quotes from "Inactivation of pathogens in EcoSan latrines"

It was found that pathogen concentrations were significantly related to time in months. As storage time increased, there was a reduction in log concentration of pathogens per gram of sludge.

Since EcoSan sludge has been found to still contain high Hookworm eggs, E. coli and Salmonella even after the waiting period of more than 12 months, protection during handling and use in agriculture is important. Storage time of 12 months or more is recommended.


What the community actually need to know is how long it takes to inactivate pathogens. We don't want to know that they are not all inactivated after 12 months. That is not a result.

What we need to know is how long it takes for die off of pathogens in decomposed human excreta. Not how long once the vault is closed, because there is an unknown period of time for decomposition to take place (especially of the contents at the top). I have been careful to say this all along, "pathogen levels reduce over time in decomposed human excreta", not something like "pathogen levels reduce over time in stored human excreta". Yet the study didn't measure decomposition. At what point in that 6 months or 12 months was decomposition complete?

One could say that because the pathogens weren't all inactivated after 12 months that this is evidence that they will never be inactivated, but that is an untested hypotheses. The scientist seeks to answer the question and in this case the testing should have continued well past 12 months, to model the pathogen survival curves. Why didn't it?

Seems to me the community remains in the dark. The users of these latrines don't know how long EcoSan compost should rest once decomposed and so the risk remains. How did the researchers come up with "Storage time of 12 months or more is recommended." I don't see the science to support that assertion. Conclusions need results that support them.

That it took 17 years to refute the 6 month "safe" storage period is a black mark on the sanitation community. That we still don't know how long it should rest is a travesty.

Whats worse is that apparently we haven't even moved forward on understanding conditions that influence survival of pathogens over time, especially temperature and moisture content in stored humus/compost. I want useful results, results that actually contribute to knowledge. The academics need to know our requirements and take these into account in their experimental design.

cheers
Dean

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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)

Faeces "composted" at low temperatures has not decomposed.

The listed survival of helminths in the WHO standards for soil have no relevance to faeces. Clearly it has been shown many times that the survival time they have for faeces is much too low.

I'm not contributing to an irrational attack on researchers who are testing systems in use because someone else insists that there is some lengthy storage time that will kill all Helminths.

With respect to what Elizabeth says, that's all I am going to say.
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