terra preta/ clivus minimus (building a composting urine diversion toilet on a farm)

  • pjeterschorstein
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terra preta/ clivus minimus

Hey all!
I read through this forum and learned a lot. I know it's a beginner question as some of you work in the field.

I am interested on building a composting urine diversion toilet on a farm. I went through a lot of reading and am still somewhat confused. To begin with I need to choose between aerobic and anaerobic toilet. I am doing it all DIY so I would like to find a good process that would ultimately yield the best soil/fertilizer for the farm soil.

I was leaning at the beginning on the clivus minimus design as it looks efficient and without too much handling it.
I came across thogh with the terra preta concept and through that to the anaerobic toilets concept (I use my kitchen scraps for biogas so I am familiar with anaerobic digester)
But it left me pretty confused as to how the method go, it looks like a complex process and I would like to perhaps be helped to implement it more easily, to find a compromise between the methods or to settle on one so I'm gonna shoot up some questions hoping this community could provide me with some guidance :)

To begin with, the Clivus design looks to me as it actually just dehydrate the compost or am I mistaken? would this design allow the use of the compost for food plants? would adding of biochar to the compost help in preserving the escape of nutrients ?( I have a woodgas stove that I cook on)

As for the terra preta, how do I inoculate with the lactofermenting bacteria, could one produce the inuculum diy? what kind of amount is needed and is it worth it?

I came across designs of anaerobic composting toilet that do not use the lactofermenting bacteria, instead the wast material is stored in a air tight container (some said with open bottom with brown leafs and soil) to a period of12-18 month. would this be a more accessible way to compost? (same question about adding biochar)

Thank you
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  • bsoutherland
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Re: terra preta/ clivus minimus

Our Rwanda farmer version of a Terra Preta toilet uses charcoal made from crop waste in both UDDT containers. Charcoal is added as needed to control odor and splash. The urine container produces ready to use nitrogen and phosphorus inoculated biochar. The solid waste container takes longer to fill and is heated to 65*C for one hour for pathogen kill off. The heat source is solar or charcoal briquettes made from 95% crop waste charcoal and 5% of the afore mentioned pasteurized poo as binder. 65*C is easily attained in a boiling water bath with a steam cover. Since the temperature needed is lower than the melting temperature of plastic, plastic poo containers can be covered and treated without dumping. This reduces exposure risk.
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  • JKMakowka
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Re: terra preta/ clivus minimus

For Terra Preta have a look at the quite comprehensive overview on SSWM:
www.sswm.info/water-nutrient-cycle/waste...rra-preta-sanitation

Judging by your username (German or Austrian right?) it should be easy to get lactic acid bacteria, just buy/make some fresh(!) Sauerkraut.

Microbiologist & emergency WASH specialist
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  • pjeterschorstein
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Re: terra preta/ clivus minimus

Thank you bsoutherland
JKMakowka, that's a good document, thank you.
As for the inoculum, I also ferment sugar for distilling. I sometime use yeast inoculum (starter) I keep in the fridge from a previous batch. I use it on simple sugar wash made of white sugar, tomato paste for the yeast nutrition and some lemon juice. Would something like that work to make more lacto-fermenting mix to save on edible material or do I have to use sauerkraut each time?
Thank you.
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  • JKMakowka
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Re: terra preta/ clivus minimus

The yeasts for alcohol production are not at all the same as the lactobacillus that you need for terra-preta. I can't give you exact instructions how to cultivate them best, but fresh Sauerkraut and some some yogurts should do as inoculum for your batch cultivation. Sauerkraut should have the advantage that you can store it quite well.

Maybe this article can be a good starting point for developing a protocol:
www.tuhh.de/t3resources/aww/publikatione..._A_Yemaneh_et_al.pdf

Please share any outcomes with us here :)

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  • pjeterschorstein
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Re: terra preta/ clivus minimus

Thank you. One thing that I cannot find is do I need an airlock in the close compost container, won't they produce gas?
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  • JKMakowka
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Re: terra preta/ clivus minimus

What kind of gas do you mean? Lacto-fermentation might become partially aerobic and thus produce some CO2, but not much other gases that might be a nuisance. But in the end you will have to experiment a bit I guess.

Edit: the low pH should mostly suppress the release of smelly NH4 and in general urease activity should be minimal under optimal Terra Preta conditions I would assume.

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  • canaday
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Re: terra preta/ clivus minimus

Dear Pjeter,

Welcome to the Forum and congratulations on deciding to apply Ecological Sanitation.

I just want to mention that there are simpler options that you can read about on my blog, www.inodoroseco.blogspot.com .

Also, in terms of lacto fermentation, search for Nadia Andreev here on the forum.

Please let us know how things go.

Bsoutherland's process of cooking/pasteurizing feces is very interesting, but seems like a lot of work and may consume more energetic resources than necessary. Are there videos or webposts on this process?

Best wishes,
Chris Canaday

Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com
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  • bsoutherland
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Re: terra preta/ clivus minimus

Hi Chris,

Thanks for your comment and interest in our sanitation process. I admire your work and devotion to simple ecological sanitation.

Sorry no video or website for our system. On sunny days, a simple box solar oven can attain pathogen deactivation temperature. 65*C for one hour is the current CDC recommendation for pathogen kill off. We use a water/steam bath over charcoal fire on cloudy days or when we are in a hurry. Since we use the pasteurized poo as a binder for making charcoal briquettes (5% poo/95% crop-waste charcoal), we have a ready supply of fuel. It is also possible, but not yet practical to use the excess heat from our crop-waste charcoal kiln to cook the poo.

Since our customers are farmers, they empty the 10 liter urine container and use the inoculated biochar for fertilizer. When the poo containers is full, we pick it up. We cover this 20 liter plastic bucket, transport it and heat treat it before dumping so exposure to pathogens is greatly reduced. Since the melting temp of the bucket is way above boiling, plastic works fine. Our latest UDDT is simple to make from locally available materials for less than $20 US.
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  • hajo
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Re: terra preta/ clivus minimus

dear bsoutherland,

because you report heating the 20L bucket with the faeces to 65C for one hour for hygienisation, I want to alert you on two postings which deal with this matter: I have been also invloved in the trials of drying/hygienising FS in a plastic container in a solar oven in Namibia. We observed that the temperature in the FS never exceeded 45C even when the temparature in the container (above the poo) was 120C (see #24193 .

I have this discussed with SeptienS who did a master thesis on the LaDePa which also dries and pelletises FS and he had two explanations for our observation: 1) heat transfer slows down between inside and outside the FS as soon as a crust has built on the FS and 2) the wet-bulb temperature of the FS keeps the temperature down, i.e. the evaporation of the water cools the core of the FS (like sweat on your skin cools you). You can read more on this here: #25299 .

Thus be careful, whether the contents of your bucket has really been hygienised by your process.

ciao
Hajo

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Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
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Everything should be made as simple as possible, but not simpler. :-)
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  • bsoutherland
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Re: terra preta/ clivus minimus

Thanks so much for the warnings. This is serious, dangerous business. We put a temperature probe into the center of the bucket as it is being heated. Also this is feces from a UDDT. The moisture content (therefore total mass) is not as high as FS containing urine or flushing water. It still takes a lot of heat to get the temperature up. To be honest, we have not yet created a completely satisfying solar solution. Using solar for preheating is pretty easy and straight forward. We finish off in our charcoal powered steam bath cooker. We plan on trying a new solar configuration in September. Sanivation has demonstrated several effective strategies for reaching hygienisation temp and time with solar. We are still looking for the sweet spot of simple solar treatment of 20 liter buckets without emptying into another vessel.
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  • hajo
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Re: terra preta/ clivus minimus

Dear Bruce,

thanks for the response. I guess we should stay in contact as we seem labouring on similar tasks.

When you say that you probe the temperatur 'in the center of the bucket' does it also mean 'in the middle of the poo'? Because then I would not be so much concerned as you seem reaching the 65C in the poo, not only in the bucket as in our case.

Your case may be a bit different as you process dry UDDT matter, while in our case the 'FS' is from Otji toilets which do not separate faeces and urine 100% but about 20% of the urine still ends in the faeces making them more dense and compact and difficult to dry. Do your users add toilet paper or wood chips which also serve the bulking of the dry matter supporting the drying process?

Can you refer me to links on the internet when you talk of SANIVATION strategies?

And I am curious to hear about your coming trials drying faecal matter in the original container.

ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
Albert Einstein
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