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Solar composting toilet

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I have pans to build a solar composting toilet, facing south, with a grid catching the manure over, probably concrete over rocks. The grid would have a glass cover to aim sunlight at the grid. Manure would fall through the grid as dust onto the concrete.
The Nearings put a lightbulb under their grid, to provide heat and keep manure from freezing in the winter. This is where I got the idea of adding sunlight and heat.
Do you think this would work? If it got TOO hot, you could lift the glass up.
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I think the grid plan deters microbes....they will be fried to a crisp. To get a good quality compost from human manure you need those microbes present. Also, I dont think sh*t cooked by the sun would smell very pleasant and I doubt the result will be dust. It will probably end up as large, rock hard clumps stuck to the grid which would probably need scraping. Possible ways to keep the manure from freezing are to bury the collection bin in the earth a few feet leaving one side exposed for access...the temperature is stable underground.
Greta Fields
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Oh. I just recall reading where the Nearings had trouble getting manure to dry. They had a bin on the side of a house split level house, looks like. It was not underground though.
If I put a toilet on the side of my house, which is split level, the manure would be facing east, but the sun quickly passes behind the house and it is back in shade.
I don't really know enough about the microbial activity to discuss this. I plead ignorance for now!
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Hello Greta! I have just come across your posts and love what I read; - so much so, that I had to read on,... and on...everything you posted:" ) -

Having helped build some sustainable homesteads with alternative building techniques, (among them an earth ship), as well as
done a lot of restoration with environmental retrofitting - all of them with with extensive water- and resource recycling,
I found, after all personal experience with compost toilets as well as black water plant beds with prepended 3-chamber separator/digester/decanter tanks,
that, with the abundant amount of free water available - even in arid areas - through good water management and recycling,
the only remaining compelling argument for dry composting toilets over grey-water toilets with treatment in black water planters
was the need to have sedimentation tanks emptied out periodically by a contractor, - which would so totally not fit in with the aim for self-sufficiency.

So I kept searching for an alternative that would combine "the best of all worlds": - the ease and convenience of a (grey-)water flushed toilet
which could use ubiquitously existing toilet and sewer pipe installations, plus "living machine" black water treatment in planted beds,
with the simplicity, ecology, sustainability and self-sufficiency of a composting system for the residues of human manure.
I finally found the perfect, most simple, hygienic, and virtually maintenance-free solution here:

The manufacturer of these rotting devices is a German company, who specializes in small to medium scale sewage treatment,
especially with planted black-water clearing beds. There seems to be no translation on their web site, but the essence of what it says is this:

Rotting units
- the sensible alternative

Instead of an anaerobic three-chamber digester/decanter tank, these rotting units use an aerobic two chamber strainer,
which acts as a separator for solids too, but also as an integrated composting bin with plenty of oxygen,
- without any additional technical or energetic input - while eliminating the costly need to have sediments pumped out .

While one chamber is being filled for about a year, the material can complete its two year composting cycle in the other chamber.
The fluid phase drips out and is being directed via pipes into the planted black water bed.
Thereby, the black water remains in an oxygen-rich state (4-6 mg/l O2), which enhances the cleaning action of the planted black water beds
and also inhibits the development of undesirable odors.

Because it is a closed system, this procedure is - contrary to complete sewage processing on reed beds -
hygienically unobjectionable. (Actually, the output after the post-treatment of the liquid phase
in planted backwater beds easily meets and often far surpasses the stringent requirements for swimming lakes.)

With gravity feed pipes or a solar pump the operating costs are virtually zero; and
apart from taking out a small amount of ripe compost once every two years, this system is virtually maintenance free.
The ready processed compost has the consistency and smell of fresh woodland soil and can be used as
an instant high quality fertilizer in landscaping,

Compost sacks

The container model, employs sturdy, non-rotting compost sacks.
The manufacturer can also supply custom made sacks according to your specifications for existing units.

Further pictures are here:

or from different sources here:

and here:

Something like this can relatively easily be self-built and installed. The essentials are just an enclosure such as a concrete pit/cistern
with two perforated inserts, hanging above or standing on a filter medium (such as scoria,..) above the floor of the enclosure.
This could relatively easily be improvised such as with a discarded laundry machine.... or any other perforated container...

This rotting double-chamber is connected near the top to an incoming sewage pipe which can be moved between the two inserts.
the outlet needs to be on the bottom, and can either be realized simply as a pipe with continuous flow into the planter beds,
or - a little more elaborate for better efficiency - a pipe into an intermediate fluid collection container, which is being emptied periodically,
controlled e.g. by a siphon with swimmer, and gravity fed into lower black water plant beds, - or by a (mechanically triggered) (solar) pump.

In equation of efficiency, hygienic aspects, comfortability, low to no maintenance requirements, and environmental impact,
this kind of solution for human manure treatment is from my experience simply unsurpassed - perfect permaculture design.

(- No, I have no affiliation to any of the manufacturers of this kind of systems: ) -

If you think it's not for you, - maybe it still gives you some fresh ideas...

Blessings to you!
Greta Fields
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Thank you. Sprechen sie deutsch? I do not speak German well enough to read the directions, but I get the gist of this system. I looked at the websites you posted trying to figure out how the sewage gets to the system? Is it still using water to move the solids to the chambers?
I wrote a lot of news articles about city water and sewage treatment systems, and this seems to be a modified version of what cities do.
I am using septic tanks, which were installed about 25 years ago and still work okay. I just want to get rid of them because they are not the best system.
I definitely want to try collecting humanure somehow. I experimented by adding it to one garden, and that garden grew giant onions (: )
I live on a hill, so I could use such a system, but I would have to run the lines a long way, because there is flat yard between me and the hill.
There are people using a system similar to this at ASPI, an alternative energy experimentation group. They have sewage running off a mountain onto small terraced wetlands, if I remember correctly.
The problem I have with wetlands is, you lose the benefit of urine. Urine is a great fertilizer when diluted. I collect it on purpose to fertilize certain plants. I haven't found a good collection system yet for urine though. It's a bigger problem than solids.
I apologize for the delay in answering. I was gone all last week and did not have a laptop computer with me.
Gioia De Amanti
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Hello Greta,

Ja, ich spreche Deutsch: ) - aber woher kannst Du so gut Deutsch? -
The system as a whole, - and in particular the black water treatment in planted beds and final "polishing pond" - is indeed similar to what many city works do:
It uses water flushing toilets (which employ preferably pre- processed greywater), and leaves the house through the existing sewage pipes,

- with the difference, that the solid separation phase is not an anaerobic sedimenter/digester/decanter / or a septic tank on a private property, respectively,
(which produce a fairly toxic sewage sludge to be pumped out periodically and dealt with as special refuse / hazardous waste), - but..

...in this system the solid separation takes place aerobically in what is basically a strainer, holding back what you would collect in a composting toilet,
(just - as opposed to that - without the need to manually empty out bins, as the compost material is collected right where it is going to be composted).

The watery phase, that is in excess in this process, is being fed via gravity or a pump either directly onto the planted purification beds
or collected in an intermediary container to be emptied out periodically in gushes, controlled via mechanical or digital-electrical valve.

So, if you don't want to "waste" urine onto the black water planters, you could use two different toilets for different purposes:
-> one set up like a composting toilet with just a local collector solely for the liquid nitrogen concentrate,
(or even peripherally outside the house by T-ing off the sewage pipes from one existing toilet to empty into a separate receptacle or tank, wherever you need them);
-> and one (for solids or mixes) connected to your old sewage pipes, which you connect (in place of the septic tanks) with the composting "strainer",
the liquid effluent of which is connected (with or without intermediate collection receptacle) to a black water purification plant bed
(- basically just a shallow pond with pond liner, filled with some high-surface drainage, topped with soil and planted -)
and that again with an overflow, either into the landscape or - ideally - into a "polishing pond" and from there wherever you want.

The great difference between this system and the septic tank solution is the replacement of anaerobically produced toxic sludge waste
with aerobically composted naturally ripened "perfect" humus to be emptied out only every two years by You instead of a contractor,
as a relatively modest bucket full of quality fertilizer with the consistency and smell of fresh woodland soil.

The great advantage over the average dry compost-toilet is evidently the eliminated necessity to handle or otherwise deal with or care about
any human wastes before they are completely composed and ready to be harvested as fertilizer.

[Not knowing ASPI and their chosen system and not knowing if I understood you right, I'd say:
The difference between the above described system and a completely "open" blackwater processing directly on planted beds, without prior solid separation is
the hygienic factor, which makes this latter approach from an epidemic as well as environmental safety standpoint plain unacceptable.

A blackwater processing without prior solid separation on uncontained wetlands (instead of contained planters) would in my understanding be flat out
environmentally criminal.]

Hearing about your particular situation, it sems that this kind of replacing a septic tank by a strainer-compost box - and maybe an extra urine collector -
would allow you to leave all installations (and convenient routines) in place and still fulfill your wish of getting rid of the cumbersome and not-so-sustainable septic tanks.
- And that all with minimal financial input. (As said, we created something like this -except for the pond liner- from scrap materials and it just works...

...and produces great amounts of organic material which we used as building material (reeds) and to build fertility - from the black water alone without the solids).

Anyhow, I would love to hear what you think and in the end decide for!

Best, Gioia.
Greta Fields
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Hi Gioia.
ich spreche deutsch nicht so weil. ? Ich vergesse.
It looks like they are using "basket strainers" that just lift out of the concrete basin? I was trying to figure out how to get the finished compost out of the basin. I suppose they are using metal mesh baskets.
This system would work where I live maybe, but I would have to remove the cover on the septic tank and put the strainers down in there, and run the liquid out the other end downhill.
I have one ditch for greywater coming out one kitchen pipe. The bathroom is on the opposite side of the house from the kitchen. I could re-route the greywater from the kitchen through a pipe running under the floors, but those pipes would freeze without heat tapes on them. I used the same heat tapes for 20 years on one house, so they are not so bad to use, but not sustainable either.
So far I have been lucky -- I have never needed to clean out lines or tanks, but we put in apartment sized tanks. They work fine. If I had crowds coming up here, I would rather have composting toilets though, because visitors will stop up toilets with paper, pill bottles etc.
I will keep on using septic tanks. I am not under pressure to switch them out. However, I like the strainer idea a lot. I think that would work in a regular composting toilet too. It would make diverting urine so much easier. I could use the bathroom greywater to flush the urine on out to a drainbed, while saving solids in a strainer under the bathroom. it would make a good system maybe.....easier to collect manure.
Gioia De Amanti
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Hi Greta,

Yes, the company I posted the link to uses either lift-out basket type strainers,
or alternatively they offer "Rottesaecke" (= sturdy and durable non rotting permeable bags - see picture),
- which might make it significantly lighter to lift the ready processed compost out and carry it around the garden.-
They also offer them custom made for existing systems, too (why not for composting toilets ?).
- I'm sure you could easily make such yourself, too, if you found an appropriate fabric.

Of course you can flush the toilets with any water, - grey- or rain- or even drinking water if you have no limited supply,
as it sounds in your case: ) -

In one house we worked at, we put the existing grey-water drain from shower, and bathroom sinks
(kitchen drains always went through the black-water processing, because of the oils they may contain)
through an outdoor grey-water planter on the south side of the house, which wouldn't freeze,
- but that was in an area where it rarely gets under freezing temperatures and virtually never for long times.

In another house it was decided to put a green house addition on the side of the house to put the grey-water planters in,
which would provide a large part of the home's food year round - like an "earthship" system retrofitted onto a "regular" timber frame house.

But if you have no shortage of water, and are in no need to re-cyle water four times, before it leaves the property,
it might make most sense for you to just use rain or drinking water for toilet flushing, as you probably do anyway, and recycle all once more for watering the garden...
(If your property is large enough, you probably don't encounter the case of having too much grey-water for watering, either -?)

If you think it's easier for you to convert from flush toilets to manually taking out manure from a collecting bin under the toilet
instead of putting the strainer/solid collector outside in or above the ground, strainers in that compost toilet could sure make separating liquids easier
(whereas the liquids would most likely not be pure urine).
For me personally a lot of the beauty of the strainer system was in that it combined the "neatness" and convenience of a water flushed toilet
with all the environmental and self-sufficiency benefits of a composting toilet, without ever having to touch anything but the ready compost.

Without taking the septic tanks out or having to convert them, you could also just put a separate - even self-made - container with strainer or strainer-bag
outside and T-off the sewage pipe to connect with that. (Just thinking as I am visualizing your description..)

All the best,

Greta Fields
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Yes, I see why you really like this concept. I think it would be a great way to convert existing septic tank systems in urban areas.
I could probably just dig up my tank, remove the lid and convert it to the system you are talking about.
I probably won't. I DO have a lot of room. I run my grey water across a down sloping field into a very long open trench that is supposed to have gravel and/or drainage e pipe in the bottom. I have never seen water actually come out into the ditch. It dissipates long before it gets that far.
I have a small grey water drain on the side of one house, however, and it just comes out right in the middle of a garden. It carries water from a kitchen sink, but it has never hurt my garden. I am a pretty clean eater....not that much oil from meat or anything nasty. In fact, there is no scum in the garden there. ]And that's the beauty of being mainly vegetarian, haha....clean sink water.]
One reason I am sold on composting toilets is, I have houses which are split level. They are 5 feet off the ground where the bathrooms are, so I already have a place for the compost to drop upon a grid, or like you suggest....a strainer. I am definitely going to think about using a strainer more.
I was gone 3 days to the city, so I did ot answer your last post right awy.,
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