A new and "better"? batch composting toilet design

Design, build and install a low cost batch feed composting toilet.

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STisdell
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A new and \"better\"? batch composting toilet design

Postby STisdell » Fri Oct 25, 2002 5:48 pm

Having been inspired by Jenkins "The Humanure Handbook" I started nearly 3 years ago the 5-gallon sawdust toilet in my home. I finally realized full acceptance of the "not told to the general public" toilet when my wife asked one of the kids if they flushed the composting toilet? Knowing that toilet couldn't be flushed, I was confused, so I asked what she meant. She replied that that was easier way to ask if they covered up their job. That made my day Image.

Anyway, with 5 to 6 adult size people in the house, I am now looking for a better way, especially in the winter when the buckets freeze before I can clean them. (I live in Northwestern Wisconsin)

Over the past 7-8 years I have been looking and thinking about various composting toilet designs. After reviewing the information on this site, I believe that for my situation, the batch design may be appropriate for my situation. I have been unable to justify any of the commercial systems because of size, cost, electric heating elements, and direct mechanical venting of heated air without an exchanger. The Biorealis design addresses each of these concerns.

Bob-I would like to discuss more of the modifications to your composting toilet that you proposed in the email as well as any success and failure stories that you may have on existing systems similar to what you describe in your web site.

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Bob
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Postby Bob » Sat Oct 26, 2002 7:33 am

Hi Shawn,

Nice to see you here. To bring others up to date, here is a description of the current system, and here is what I said in my email: <blockquote>"In fact I'm in the process of designing a new, improved version for my own house. Having experimented with the low-flush (Sealand) toilet model for the last few years, I've decided that I want to go back to the open chute model that I had previously -- but with improvements: The new version will consist of modules as before, but with three smaller ones (fabricated inserts inside of 55 gal plastic drums), rather than the two larger ones described (55 gal drums inside of 80 gal PE tanks), on a carousel with (urine-separating) open chute above. And lined with (easily cleanable, non-stick) UHMW sheet. Perhaps we could each build one, document the construction & share our experiences..."</blockquote>. With that out of the way, what kind of space do you have available for installation (of either system)? The original design (that I have built and have experience with) needs a minimum of 30" x 30" x 72"H per module. That's minimum. You'll also need room to get them in and out, and to work around them. The enclosure I have (had) them in measures 36"W x 60"L x 78"H. The entire front is removable. Here is a picture (but note that what you see inside the enclosure is not the composter. It is this digester).

Image

STisdell
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Postby STisdell » Sat Oct 26, 2002 8:49 am

Hi Bob and all. I get quite a few chuckles about my bumper sticker "Compost Happens." Carla Emery, author of "The Encyclopedia of Country Living" gave it to me when she saw me drooling over it.

Space limitations for composting: I will have at least a 6' by 6' floor space, ceiling height is 6' but from 5' and up there are plumbing and ducting lines to contend with. The composting enclosure would need to be built to allow future access to these lines.

Is the 6' height needed for removal of the inner tank? If the tanks are on castors, and removal occurs upon cleaning the inner tank, I could move the unit outside of the housing where I would have 6.5' of headroom.

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Bob
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Postby Bob » Fri Nov 15, 2002 1:47 pm

Hi Shawn,

Sounds like the 6'x 6'x 5' work space you have available should work fine. Do you also have free access to at least one side of the enclosure, to allow removing and replacing drums? Ideally, you should have room to maneuver a hand truck able to handle a drum that weighs >150 lbs (volume of aged compost is considerably reduced & lighter/dryer than a drumfull of fresh material which weighs more like 400-450 lbs).

"Is the 6' height needed for removal of the inner tank?"

No, just for maintenance/working space above the top of the drums/modules. (You want to be able to inspect the contents of a drum without having your face 12" from it... :-)

"If the tanks are on casters, and removal occurs upon cleaning the inner tank, I could move the unit outside of the housing where I would have 6.5' of headroom."

The idea I've been working on has all three drums mounted on a single rotating 4' diameter disk. What I did with the earlier model was to remove modules to a completely remote location and tip it over to dump out the aged compost. (One of the problems with that design was that the larger tanks were to heavy to move easily.)

So far, what I've done is to cut two disks from a sheet of 3/4" CDX plywood, then glue and screw them together to make a very solid 1-1/2" thick platform. (But your idea of having each module on it's own wheeled base is interesting, and maybe simpler...)

Pictures & more details coming soon. I've been working on it in spare time, got one half-built...

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Bob
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Postby Bob » Sun Dec 08, 2002 9:57 am

Hi Shawn,

I've made some progress on the new composter. A (preliminary) write-up and construction photos are here

STisdell
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Postby STisdell » Mon Dec 09, 2002 4:02 am

Excellent work Bob! You didn't just make "some" progress, you made GREAT progress.

Construction of the modified composting toilet system looks within my skills. I am in the progress of making room in my basement for the system. I should have appropriate access space. I think my biggest challenge will be convincing my wife that we can be completely weaned from the porcelain throne and that guests will accept an alternative. If all else fails, we can still switch back and chalk it up as a learning experience.

A few questions I am thinking on are:

  • Urine separation for females? Is the funnel really no problem?
  • How will special needs people use or misuse this toilet? (I will make appropriate modifications as needed)
  • Does much of the urine get evaporated from this system? I would not relish carrying out buckets of urine, that is what I am trying to get away from.
More questions/comments to follow.

Shawn

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Bob
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Postby Bob » Mon Dec 09, 2002 9:44 am

"Urine separation for females? Is the funnel really no problem?"

Good question, Shawn. I don't know yet. I've bought three different sizes of funnel, heated, bent & attached them at different heights & angles inside the chute, discussed the issues with my wife. Seems to me that the trick is to get the funnel as large as possible but not so large that there's much likelihood of it getting hit with feces. I'm thinking it should cover about 1/2 or maybe a little more of the total diameter, maybe 4"-6" down from the top. Maybe we can get some expert opinion here. I'm also thinking that the funnel needs to be easily removable & cleanable, for those occasions that someone does miss (e.g. smaller children who may sit too far forward on the seat? explosive diarrhea?).

"How will special needs people use or misuse this toilet?"

I guess it depends on the special needs. Could they use an 'accessible' outhouse? What I'm building is essentially an indoor outhouse, a simple bench with a hole in it covered with a conventional toilet seat & lid. Flushing involves tossing a scoopful of sphagnum moss (from a crock on the bench) in the hole after use.

Seems to me that for ADA, the seat should be a little higher, wheelchair access and grab bars provided?

"Does much of the urine get evaporated from this system?"

No. I'm just diverting it to a small drainfield & disposing of it. But only because I don't have anything better to do with it in my current setup. If I were designing an ideal system from scratch, I would divert it to a separate drum with some means of diluting it with fresh water (e.g. a conventional toilet tank float & valve) and pumping it immediately to a subsurface irrigation system (before it loses its N). Or something like that. Something to invent next...?

"I would not relish carrying out buckets of urine, that is what I am trying to get away from."

What are your options? Would something like a garden irrigation system be feasible?

[This message has been edited by Bob (edited 12-09-2002).]

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Postby Bob » Mon Dec 09, 2002 11:29 am

Here's a sketch of the toilet chute showing the funnel. So far, what seems about right is an 8" dia funnel flattened into an oval so that it fills a little more than 1/2" the diameter of the chute, (say about 7"?), mounted about 3"-4" down from the top. What do you think? any consensus of opinion -- especially from any female members of the audience? What would be the optimum values for 'x' and 'y' in the following sketch?

[img]/forumuploads/urinechute.jpg[/img]

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Laurel
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Postby Laurel » Mon Dec 09, 2002 2:41 pm

I'm a lady, and I thought I'd add my Number Two Cents...

I just got the ruler out and did some empirical measurements. The value for x in the above drawing should be no less than 4 inches. Actually, 4 inches was the distance from the urine stream to the inside diameter of the toilet seat, so be sure to add another inch or so for variation. This also assumes an adult female, having positioned her body with respect to the back of the bowl. (I mean, when one goes to sit down, the reference for where to sit depends on how far back it takes to make a nice seal.) The length of my toilet seat hole (front to back) is 10 inches. Given the 4+1 inches for the front, that leaves 5 inches for the back. As far as how low to position the funnel, it's probably best to assume that the urine stream goes straight down. Of course, there may be a bit of an angle, depending on how forceful the stream is... But if you're making assumptions, straight down is conservative.

(oops... potty break...)

Having just observed my own habits once again, it seems that the longitude of the toilet seat would be a major factor. Positioning oneself on the bowl depends on what needs to be done. It seems to me that the user will need to scoot forward or backward depending on need. So, I guess it's important to make the funnel (value x)at least 5 inches (and a woman can scoot forward in order not to miss...)

Hope this helps.

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Bob
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Postby Bob » Mon Dec 09, 2002 3:09 pm

Hahaha. That's great!

Yes. Thank you so much, Laurel.

(It's kind of hard to do this with a straight face, isn't it... Image)

Ecowaters
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Easier Carousel (batch CT)

Postby Ecowaters » Fri Feb 13, 2004 4:31 pm

Just a reminder that the name Carousel is the name of a manufactured system on the market for 30+ years in the U.S. and a lot longer in Scandinavia. See http://www.ecotechusa.com

The barrel system here is neat, but when we had to simplify our large-capacity system for my projects in Mexico and for a resort in Fiji, we simply used one barrel. We use dry toilets stools, microflush toilets, Norwegian dry rotating bowl toilets, urine diverters and urine-diverting toilet stools. It all works. It's easier for me to just wheel the barrel away when it fills.

I used to make urine diverters with funnels for Mexico and my home but found it was so much easier to use the prefab ones because they're ergonomically correct and look like a finished piece.

Some good urine diverters:
http://www.ecovita.net (click on Privy Kit-- you get plans for a urine-diverting batch CT system with it) (they also import fiberglass u-d stools sometimes)

http://www.ecotechusa.com (U.S. distributor for Ekologen, http://www.wostman-ekologi.se)

Best,
Carol Steinfeld

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Bob
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Postby Bob » Mon Feb 16, 2004 2:09 pm

Hi Carol,

Nice to see you here. Re use of the word "carousel", even though it is in the dictionary, defined as "A circular conveyor on which objects are displayed or rotated", I suppose that, to avoid even the potential for confusion (or legal action), I should refer to it as a "turntable", or "lazy susan" (heading off to find thesaurus :-?).

The barrel system here is neat, but when we had to simplify our large-capacity system for my projects in Mexico and for a resort in Fiji, we simply used one barrel. ... It's easier for me to just wheel the barrel away when it fills.

Where do you wheel it away to, and how much does it weigh? Do you have some separate place to store barrels to allow them to complete aging? Or, in those hot climates, is the content already well decomposed? What do you do with it when you wheel it away?

I too have experimented with single barrel systems, but generally found (at least for my specific site conditions) the maintenance requirements to be more time-consuming, and a nastier, more difficult job. The barrels to be moved were very heavy, full of only partially decomoposed shit, and they needed to be moved to some other location to finish aging before they could be emptied. The 3-drum rotating turntable, combined with urine-separation (greatly improving the C/N ratio and reducing the moisture content) is an attempt to simplify that periodic maintenance, though, admittedly, at the cost of a little more initial investment and complexity.

I suppose that, on one level, I could agree with you that "It all works", but I can also say that, in my experience, every one of those choices (e.g. between dry toilet vs microflush, urine+feces vs urine-separating, etc.) has significant consequences. I have seen many installations that would be perfectly workable in some situations or acceptable to some end-users, that a different person in another situation would consider a failure. (Rural Alaska is littered with such "failures".)

Some good urine diverters: http://www.ecovita.net ...

Great! Thanks for the link. (I just placed an order for the Separett privy kit -- and your book.)

eliza
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Re: A new and

Postby eliza » Sat May 24, 2008 9:20 pm

Hello,
I am writing from a small kibbutz like community in Alaska (see http://www.ionia.org). We have 50 people in 9 homes and a large community center using outhouses equipped with 5 gallon buckets and use the composting system as described in the humanure handbook.... we are looking for a better system that is easier to handle in the winters without resorting to electricity, or heated outhouses. Can you help us out?
Thanks so much,
Eliza

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Bob
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Re: A new and

Postby Bob » Sun May 25, 2008 11:22 am

Hi Eliza,

Nice to see you here. I would need to know more about your specific site conditions to be able to say if, or how well my rotating drum, urine-separating design would work for you. Probably the single most important criterion is to have accessible space for it directly below the toilet. However, even if this particular design couldn't be used, I could probably help you design something else that might work better for your application.

I'm also excited to learn about your Kasilof community. Thanks for the pointer. (Having lived here in Alaska for over 40 years I'm wondering how I could have not known about it till now.)

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