Image Credit: Energy Vanguard
Image Credit: Energy Vanguard Side view of the composting toilet. Here you can see the golf-cart batteries that powered the the 5-watt fan that kept the tank under negative pressure. The reason we used batteries was so the fan would run even when the power went off.
Image Credit: Energy Vanguard Front view of the composting toilet. You can see the upper and lower access doors, the wrench that turned the axle with tines to turn the material, and the pump that sprayed leachate from the bottom of the tank onto the top of the pile to keep it moist.
Image Credit: Energy Vanguard It took four years before we removed compost the first time. It was very well composted and didn't smell anything like the stuff at the top of the pile.
Image Credit: Energy Vanguard
More Building Science
Ten years ago I was building a green home. It had passive solar features, was built out of structural insulated panels, sent all the greywater out to the back yard to water fruit trees, and was going to be super energy efficient. One feature above all others, though, captured people’s attention when I described the house to them — the composting toilet. The first reaction of many of them was:
“Ooh. Won’t that stink?”
Why bathrooms with composting toilets smell better
We installed the kind of composting toilet with a large tank in the basement. The tank had a small fan that constantly exhausted air from the tank through the vent on the roof. So, whenever anyone went to the bathroom and … uh … did their business, the bathroom smelled better than before they went in there. The reason is that as soon as they opened the lid on the toilet, air from the bathroom was being pulled down through the toilet, into the basement tank, and then sent out through through the roof.
A lot of people are down on negativity (Say NO to negativity!), but actually it’s a good thing when channeled properly. Negative pressure inside a composting toilet means you never have to worry about walking into a bathroom that’s had all the oxygen sucked out of the air (as I heard it described once).
OK, composting toilets are about a lot more than bathrooms that don’t stink. The main reason that people who consider themselves environmentalists install them is to prevent problems associated with waste treatment plants and septic tanks. In this age of “going local,” they keep the organic matter at home (unlike a sewer system) without polluting the ground water (unlike many septic tanks).
But let’s skip over all the big picture, environmental stuff. If you’re considering a composting toilet, you want practical information, so here’s my advice to you, based on the three years I spent living in one … uh, I mean living in a house with one.
Practical advice on composting toilets
Don’t get a small one. You know, the kind that’s an all-in-one unit that just sits on the floor in any bathroom. It has a small tray at the bottom that you slide out to remove the waste. I had some friends in Florida who had one, and they hated it. You have to empty it far too frequently, and it doesn’t really get enough mass to get the composting going. And unlike the one I had, they’re smelly. [Edited 23 May 2013: I may have rushed to judgement without enough data here. See the comments from Lloyd Alter and Bruce Lepper below.]
Use compost starter. When you read the instructions for composting toilets, they tell you that you have to put some starter microbes in the tank to make the composting happen. They give you two choices: Buy their special starter or throw a shovelful of soil in the tank. We chose the latter and had a plague of little fungus gnats living in the tank. (I could write a whole article just about my battle with those annoying little critters.) I suspect that using the soil from outside was the source of our gnat problem.
Consider a foam-flush or micro-flush toilet. Some people are squeamish about doing what comes natural into a tank where they can see that other people have also been doing what comes natural. Crazy, I know, but it’s true. These types of toilets also give you the flexibility to install the toilet in locations other than directly above the tank.
In case you’re wondering, we went with the Phoenix composting toilet by Advanced Composting Systems in Whitefish, Montana. The owner had previously worked for Clivus Multrum, the big name in composting toilets. I was pleased with the design, sturdiness, and functionality of the toilet. It was also fairly easy to assemble and install (for someone who’s handy with tools and used to doing this kind of stuff, that is). I recommend checking out both of those brands.
If you’re in the Atlanta area, you can check out the Clivus Multrum with a foam flush toilet at Southface Energy Institute’s Eco Office near downtown.
Because the tank was so large and there were only two of us living in the house (for the first three years anyway), we didn’t have to empty the tank until it had been in use for four years. At that point, I wasn’t living in the house anymore but went back to help with the first removal of the compost in 2007.
It was nice stuff! The Phoenix has two access doors, an upper one and a lower one, as well as two large axles that run the length of the tank, each with several tines. When you open the lower door, you can pull out all the old stuff from the bottom and the axles and tines keep the newer stuff from falling. Cool!
Finally, for those of you who think these modern composting toilets are too fancy or expensive, I recommend The Humanure Handbook. I don’t think you’ll ever get their design approved by a building department, but it’s definitely low-tech and cheap. All you need is a 5-gallon bucket, a toilet seat, and some sawdust.
Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.
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30 Comments
Blower door testing and composting toilets
I'm a real fan (Bad pun, you'll see) of composting toilet systems. I've been involved in several projects that used them over the past 12 years or so. So far the acceptance level has been very high and the problems few and solvable.
Twice now I've pressure tested buildings that have had these in place for a couple of years. Trust me when I say that a blower door will easily overpower the composting toilet fan. I would suggest that anyone finding themselves in a similar circumstance learn the plastic wrap trick, which you may have heard of in high school or college ;-)
Basically anything that will seal the toilet opening and stay put will work. I also made a sophisticated plywood fixture, a square of plywood with a hole smaller than the toilet and the fan flow box and some weather stripping, for measuring the composter fan flow.
Just remember that you are a responsible adult and remove the plastic wrap when you're done.
a few things ...
1- what is the goal of using a composting toilet ?? i thought that toilet waste was the least environmentally damaging water/rejects from human houses ... ???
2- air exhaust fan all year long ? no HRV on that i guess...energy penalty ?
3- what is the upcost of the depicted system ?
Building department approvals
How hard is it to get a San Diego county building permit using a composting toilet?
We have two acres with a house that is way too large for us. On the far corner is a good site for a small house, but no room for a septic system between there and an arroyo. I have been thinking for years that we could build an efficient house with a composting toilet in that area and sell off the larger house to someone who still has a family or a big ego or something.
PS, Don't condemn me for the size of this house. It came along with my wife from a previous marriage and she thinks it's too big, too.
a few quibbles
I am not sure your advice "don't get a small one" is appropriate. I have a small Envirolet albeit for summer use, and only have to empty it once a year. A friend has a Sunmar in his year round house and is happy with it, wrote about it here: http://goo.gl/TJZdv Your solution requires a basement and space that a lot of people don't have. Then there is the issue of the foam flush and low water alternatives; I had one, and it screwed up the compost, too much liquid. People just have to get over this fear of poop. My friend Laurence has, in 15 years, had only one guest run for the hotel because they wouldn't use the composting toilet, it is not so hard.
I'm a fan (but don't need one for the toilet)
"Don't get a small one" was an unfortunate shortcut, which leads to the conclusion that small ones are stinky ones. For the past couple of years I've been living with the basic "Humanure Handbook" toilet which you thankfully mention in the last paragraph and there is absolutely no smell. I've been using dry grass cuttings from the mower (spread them out in the sun on a hot day) instead of sawdust, with three plastic buckets. If there is a smell, it's that of fresh hay, which is great! The only time you get an unpleasant whiff is when you empty the bucket into the compost heap, but you cover that with fresh carbon material (straw, hay, etc.) and it goes away. One tip: after washing the spare buckets, put a little hay in the bottom before sealing with the lid, which stops them creating a smell while they're waiting their turn to be used. Guests? Up to now they have all found our toilet amusing. Installation? Put it where you need it, including in the bedroom of someone with mobility problems. I too recommend the Humanure book, it's more than a handbook it's an education.
Response to Jin Kazama
The goal is to keep that stream of material from being 'waste' that has to be disposed of and treated. It's to complete the cycle on site rather than off site. In our case, it meant we didn't have to install a septic tank, and we got really nice compost to use.
The exhaust fan was tiny - 5 watts. I don't know how many cfm it pulled, but most of the time it was almost nothing because the toilet seats stayed closed unless someone was using it.
The toilet cost was about $5000US as I recall. The greywater system was probably a couple thousand. We didn't have to install a septic tank. Not sure what the net cost was.
Response to Brian Godfrey
I have no idea how hard it is in San Diego, but Art Ludwig might be a good resource for you. He's based somewhere in California.
Response to Lloyd Alter
Thanks for the feedback. I may have rushed to judgement too quickly without enough data on the small versions. I'll check with Southface to see how their foam flush Clivus Multrum is doing now, 5 years after they started using it.
Response to Bruce Lepper
You and Lloyd Alter both smacked me for that statement, justifiably. I'll add a note to the article so readers will see the comments here. I haven't tried the Humanure method, but my thesis adviser did for a while when she was building her off-grid solar home in Florida.
And speaking of the Humanure Handbook, I found this cool video the other day when I was preparing this article: Poop in a Bucket.
Bucket System
I'm really glad to see people have talked about the Humanure Handbook - I love that book! I have been living in a 120 sq. foot tiny house for two years now with a 5 gallon bucket toilet system. With two people in the house I have to empty it twice per week. It takes ten minutes, I have a second bucket that I rotate so I let them air out for a few days between uses. I built a 4x4x4 pallet compost bin out back with a sort of lid to keep animals out. It's been two years and I haven't even filled one bay. I live in Vermont and it's hot and steamy even when the temperature is way below zero. Healthiest most active compost I've ever had. It would take a lot of convincing to get me to go back to a flush toilet, I love my composter. Glad to see it being discussed more openly these days! My partner and I have written a bunch about our experience with it on our blog: tinyhouseadventures.com. You can also google Loveable Lou for great ideas on buying or building a bucket system.
Battling the Gnats
Like you, I have a Phoenix composting toilet system in my home as well . . . it's been seven years now. Like you, we are very happy with it. But, like you, we have a gnat issue. Did you ever find a remedy for them? Some other folks I know who have the same toilet system and the same gnat problem have used borax, though I don't know the outcome. I'm reluctant to try that as I'm not sure of its impact on the finished compost. I've thought about trying diatomaceous earth. Did you ever beat the gnats and if so, how?
Borax, boric acid, will
Borax, boric acid, will probably kill the gnats, but I'm not sure your wastes will properly compost. I'm interested to know. We mix roach powder (boric acid, coloring and nothing else in it) with sugar water to make a safe piss-ant poison, but have found that putting it directly onto the soil kills not only ants but most everything else. (Fortunately we tried it in just one spot first!) But I don't know what concentration it would take to kill your compost. It is a natural mineral, but that doesn't mean it is benign.
The gnat battles - response to Jeff Feldman & Brian Godfrey
We tried a lot of different ways to control the gnats. In the end, we managed to keep them under control well enough that they stopped coming into the house. My ex-wife (Did I mention that I no longer live in the house?) found a source of some natural stuff to put in the tank to control them, and we tried a few different things. They worked OK. I think diatomaceous earth was one of them but we also tried some kind of organisms that were supposed to eat the gnat larvae. Sorry. I don't recall the place she ordered from or the stuff she bought.
The population definitely went down, but I think the thing that may have helped the most was installing a 12 V light that got very hot, attracting & then killing a lot of the gnats. A side benefit of that was that it gave you a nice view of the big pile of poop when you opened the lid.
This light was a replacement for the light that ACS had installed near the fan. I should have mentioned it above, but if you have a light near the fan, you'll need to disable that immediately if you have a serious gnat infestation. All it does is to form a gnat cake that eventually stops the fan.
Another option
Thanks for this article on an important, if not always socially acceptable, topic. I also appreciated the comments, though as a gardener I would caution that borates can be toxic to some plants, and thus may affect where you can put the finished compost.
Unfortunately, composting toilets have a stinky reputation for a reason. Most of my visits to composting toilets have involved some unpleasantness. One notable exception is the “Dan Dourson Double Burner”, named for its designer, who attributes its lack of smell to three features:
1. Two side-by-side chambers, one in service and being filled, the other idle and composting its pile of organic matter;
2. Drain tile underneath the composting chambers to efficiently remove liquids; and
3. Passive ventilation of each chamber to a point above the roofline.
I’ve seen this design implemented in mountainous areas of Kentucky and North Carolina with great success, though always as an outbuilding, not integrated into the main house. A 4X8 footprint seems to be adequate for a wide range of uses, though your mileage may vary.
Construction involves the following steps:
- Excavate the footprint down about 30”, with a connected trench extending about 10 feet or more from the footprint in a direction that ensures positive drainage away from the structure and chambers at all times.
- Lay down perforated drain tile across the long axis of the footprint and out to the end of the trench. Put down about 6” of gravel around and over the drain tile, or more if using larger tile. Use filter cloth to protect the drain tile from fine particles if necessary.
- Build the perimeter walls of the foundation on the gravel to grade or higher, with a separating wall in the center that divides the footprint into two halves. For a 4X8 footprint, this would create two chambers, each roughly 4X4. I’ve done this with mortared block and mortared brick, but other materials may work, too. Especially wet sites may require additional measures to prevent infiltration into the chambers. Make sure each chamber has an opening in one of its walls to allow the contents to be shoveled out without too much trouble. Access doors or hatches that can be well secured and are not too much of a hassle to remove are also important for critter management. You don’t want anything crawling out of your toilet at an inopportune moment (… and no, there is never an opportune moment for anything to be crawling out of your toilet). A hillside site can make excavation, water management and chamber access much easier. Depending on your design it may be necessary to include openings for a ventilation duct in each chamber. Alternatively, the ventilation duct(s) can be routed through the interior of the structure and out the roof, if you’re really into flashing and sealing details.
- Build the exterior walls, entryway, and interior furnishings as plain or fancy as desired/necessary. Pay particular attention to bug screening and sound water management (or else!). Make sure that each of the two toilet openings can be unambiguously closed and taken out of service. A 4X8 sheet of plywood can be the floor, with generous openings cut out to make sure everything ends up in the chambers. There should be two such openings -- one for each of the toilet’s chambers (“burners”).
- Install the ventilation ducts, roof, and necessary appurtenances. Painting the ductwork black may help the system draft. Don’t forget the bugscreen and rain cover atop any ventilation ducting!
Now you’re ready to let ‘er rip! Operation of the unit is fairly simple -- no need to pee outdoors, or into a bottle, or any other act to separate liquids from solids. After each use place a handful or two of leaf litter or generous scoop of loose dirt into the active chamber. It is very important to avoid using water-retaining materials like sawdust, as these will increase the chance of odor problems.
When necessary, the currently active chamber is closed off and made idle, and the currently idle chamber is cleaned out and made active, usually in one operation. It may be useful to size the chambers so that the time between switches is long enough to allow the compost in the idle chamber to be completely finished and ready to put out before the in-service chamber is full.
My apologies for the extra-long comment. I hope it is helpful.
Response to C. Talwalkar
C. Talwalkar,
It sounds like you are describing the composting outhouse design promoted by Sim Van der Rijn in the mid-1970s. I built two of these composting outhouses in the 1970s, and used one for several years. These outhouses work well. We used to keep a bucket of sawdust in the outhouse, and throw some sawdust down the hole now and then.
We used the finished compost on perennials, but not on root vegetable crops.
Composted toilets on boat.
Small composting toilets have a satisfactory place on an appropriately designed boat. I made sure when building mine (a modest 25 foot power cruiser) that the head compartment was oversized, and that the solar panel (with its associated large battery) was big enough to let me run a small exhaust fan 24/7 so that the negative pressure is constant. Other than that one indeed does have to get pretty closely involved from time to time with the (composted) remains, the whole setup has been entirely practical, and much less smelly than the conventional holding tank.
Regards, Tony.
Re: Martin
Thanks for the historical precedent, Martin!
I'll have to ask Dan what role Sim Van der Ryn played in his outhouse design. He is, shall we say, an empirical learner, so it's possible he got to Van der Ryn's design through trial and error, though someone might have slipped him a suggestion or two while he wasn't paying attention.
I'm surprised to hear that this design works well with sawdust. That was one of the things Dan specifically warned against, as he had problems when he tried it. Perhaps climate factors into performance?
Response to C. Talwalkar
C. Talwalkar,
Sim Van der Ryn was associated with the Farallones Institute and the Integral Urban House in Berkeley, California. I have found only one reference to his composting toilet design on the web: on a British website, his design (the one I followed) is called a "Farallones Twin Chamber Composting Toilet."
The website notes, "This is a simple diagram of the Farallones Twin Chamber Composting Toilet. It consists of two chambers with a seat on top. One chamber is used until it is full and then covered while the other is used. When that too is full the first chamber is full of compost and can be emptied. Instructions for use are simple – keep it moist (not wet) warm, and cover the substance within with a layer of sawdust or similar after each use. However, it is necessary to turn the compost every month. Simple to use, probably more complicated to ask someone to build!"
I am attaching the diagram from that website, which is fairly low-res. I could take a photo of my own outhouse, but the photo won't show as much as this sketch.
.
Gnat problem in composting toilets
To eliminate a gnat infestation use Gnatrol WDG. It is available on Amazon.com or from Advanced Composting Systems. Gnatrol is a fungicide that kills Gnat larvae. The process that I recommend is to turn off the fan in the composting toilet and fog the top of the compost pile with a Pyrethrum insecticide. After about 10 minutes turn the fan back on and fog the air inlet to the composting toilet with the Pyrethrum. This will reduce the adult gnats. Waite at least 12 hours after using the Pyrethrum and fog the top of the compost pile with Gnatrol. We are starting to send out Phoenix composting toilets with Gnatrol as part of the package. Please contact me with any issues with fly or gnat problems. [email protected]
Thanks, Ried Nelson
Re: Martin
Yup. That's pretty much what we've built, with the following differences:
- 6" gravel base for entire structure, with drain tile across both chambers and extending along the contour (mildly down-gradient) on the downhill side of the structure about 10' or so to provide good drainage;
- Dividing wall same height as perimeter wall to provide better support for floor above, with gap(s) for adequate ventilation;
- Dry leaf litter and/or dirt instead of sawdust as a covering material to innoculate compost with bacteria and fungi without adding absorbent material to the pile;
- No turning of compost in our roughly 3'x3'x3' chambers, though units with very large chambers may need to have their contents turned to avoid anoxic conditions at the center of the pile. In cold climates, turning of the pile might be needed to ensure all the material spends some time at the core where the temps are highest and decomposition most efficient.
Never a problem with any insects or odors in over 4 years of service inland in CZ4.
Regarding Ried Nelson's entry -- the combination of pyrethroid insecticides and associated chemical adjuvants like piperonyl butoxide are not entirely harmless, especially to beneficial insects, children, aquatic organisms and cats.
Gnatrol WDG's active ingredient seems to be Bacillus thuringiensis -- a soil bacterium that kills insect larvae. Sounds better than fogging with pyrethroids, though the company has not disclosed the "inert ingredients" that make up 55%-65% of the product.
The fogging seems intended to kill the adults, while the Bt gets the larvae, hopefully lasting long enough to get any eggs that hatch later. Then you cross your fingers and hope that no mother buggers migrate back!
Convergent outhouse evolution
Regarding c talwalkar's “Dan Dourson Double Burner” and Martin Halladay's "Farallones Twin Chamber Composting Toilet," I think we're seeing some convergent outhouse evolution here. I have encountered a nearly identical design going by the name of the "Gap Mountain Mouldering Toilet," an example of which is at Yestermorrow Design/Build School in Vermont. If I recall the instructions correctly, it was sized to accommodate two years'ish of material per chamber, and no turning of the compost was required. Two years of mouldering was determined to be sufficient to convert the pile to finished compost. I think that sawdust or similar carbon was added after each use, but I don't recall. See halfway down this page, http://www.thegreencenter.net/tb/tb006.htm. Yep, this site says to add a pint of sawdust with each use to maintain proper C:N ratios.
Small composting toilets
I have to take exception with the notion that small composting toilets are not advisable. Full disclosure, I am the designer and manufacturer of the C-Head and BoonJon portable composting toilets. While it is classified as "portable" or even temporary for legal reasons, I have used one in my home for the past two years. It requires no ventilation, basement or plumbing but it is more work in that I have to empty the urine contents daily and the feces once a week with two people using it. The up side is cost, ease of installation and maintenance, and looks. It is beautiful and looks pretty much like a regular toilet. While I have to empty it weekly, this short time frame prevents the formation of insects in the toilet. I don't know why anyone would want to keep moldering feces inside their home since you will have to deal with the smell and vermin if you do. The BoonJon is a urine diverting toilet. You take the feces collection container outside to a composting tower and pour it into the a bottomless half buried five gallon bucket that is situated in the center of the pile. As the tower is filled with compostable material around the bucket, the bucket is raised and a carbonous core is formed.. The fecal contents are devoured by black soldier fliy larva which also drive away house flies by eating their larva. There is very little smell outside of the bucket and the larva convert the waste to hummus in a matter of hours. A four foot high tower will hold 6 months to a years waste for two people. The urine is poured into the tower using perforated pipe stacks driven into the compost or diluted and poured directly on the surrounding vegetation or around the perimeter of the property to keep wildlife away from the property.
If you have two conventional toilets which most homes do, you can replace one with a portable composting toilet and reduce your water comsumption significantly. The urine can be poured down the remaining conventional flushing toilet so that one flush removes the entire days accumulation for two or more people.
I have never come across a complex composting toilet that did not smell and or wasn't overly complex. Unfortunately, we live in a world where people are led to believe that if something is simple it must not be very good. The opposite is often true, especially with permaculture.
Response to Sandy Graves
I hope you noticed that I added a statement to the article about small composting toilets. The little experience I had with them led to my original warning against them, but apparently some people have had good results. Your portable units certainly sound interesting.
I may have rushed to judgment about the small units, but I have had some experience with several of the larger units, including living with one for three years. I've never noticed smells in the house or near the tank, so I'm not sure why you think they all smell bad.
Composting Toilet with no odor
I would not have believed it. I was very skeptical when my wife said we should try this. We built a cabin in East Texas last year and decided to forego a septic system if possible. Who couldn't use an extra $8K in their bank account. :) We started using a bucket toilet with sawdust that we get free from the local lumber company. We use heavy duty trash compactor bags. We had never had a problem with smell but never stayed longer than a weekend and always took the bag with us to include in our trash pickup at the house. One weekend, we forgot to bag up the half-full bucket and it got left locked up in the cabin. We had obligations for the next several weeks and didn't make it back for over a month. As we drove up, my wife remembered that she had not emptied the bucket and we were now dreading the though of opening the door and being knocked down the odor. We slowly opened the door and I kid you not, we couldn't tell that the toilet had been there for over a month. No odor! We are now starting to use the bucket with no bag and will start a compost pile here on the property. I'm sure out of 12 acres I can find a spot close to the garden. It will take a bit more sawdust to keep it covered but everything I read says the same, "there should be no odor if you just use a generous amount of sawdust." Now, we're working on building a fancier enclosure with a full-sized toilet seat and a urine diverter. It feels good to save the thousands of dollars and know that we're doing something that will be good for the environment. Keep an open mind and stop listening to all of the nay sayers. You can do this!
Jay & Kim
self contained composting toilets
Self contained composting toilets - whether they be home made sawdust toilets or commercial units - can and often do work perfectly, with zero odor. In my experience, some work better than others. I am now convinced that urine separating devices are better. No heaters, no complex rotating mechanisms - mechanical things fail. And if the urine does not evaporate quickly enough, it will never compost. It will just be a sewage tank. A urine separating toilet gets around these problems.
Look for quality. A well known brand I used to sell was prone to leaks. Typing the toilet name and 'reviews' into Google is useful.
You might not need a vent or fan, if you really bury the poop with sawdust. But think about it...it stinks inside that toilet. Where is that stinky air going to go, without a vent? It can only go one place - inside your house - unless the toilet is airtight. Now if you really bury it, you might not smell anything. But for the sake of $100 and a few hours work, put a vent stack and computer fan in there. That is the key to 100% odor free composting.
self contained composting toilets
Self contained is really my only option. Has anyone tried wind generated fans rather then electric ones or just used electric fans when the wind is too low? I keep reading about heaters; in a solar house, electric heaters, no matter how small, is a no no. Are they really needed?
Urine smell and toilet paper
Hi guys!!! Your comments have really helped me and taught me a lot. I'm a single Mama, my son is a Senior this year, and I'm totally planning on some kind of a tiny home (converted school bus, gutted Airstream, little shed, who knows???) as soon as he's safely ensconced in college. I'm pretty sold on the composting toilet, but still have a couple of questions. Forgive me if they sound stupid, but:
Even though there is a urine collection thingy that diverts the urine, wouldn't you have to wipe out the bowl or clean it out somehow after each use? I'd rather live in a bucket of crap than have to smell pee....
Also, does the toilet paper get thrown down the waste hole? Does that compost as well?
Please don't beat me up, total newbie here!!! Any insight is really appreciated, thanks! ;-)
Response to Debbie Baker
Debbie,
I don't know if you are talking about a home-built composting outhouse or a commercially manufactured composting toilet.
Most commercial composting toilets have airtight lids to reduce the chance that odors will enter the house. Some of these toilets include fans that depressurize the composting chamber so that indoor air will be pulled into the toilet. (The exhaust gases exit the house through a vent pipe that penetrates the roof.) This depressurization helps prevent odors from entering the house.
Toilet paper is fibrous and has a high carbon content. Adding toilet paper to the compost improves the carbon/nitrogen ratio (as does the addition of sawdust) -- and that helps the composting process.
small homes?
Darn great idea but this requires a basement. Are there any really good, non self contained designs that don't, and that can be had for under $1000? Also, that do not require manually removing the waste from the unit and then manually placing it into a composter? I like how this unit is sort of all in one, you drop waste but shovel out compost.
That said;
I like the idea of composting waste and tossing the compost out in yard for the grass/trees instead of having a sewer or septic system. But I personally would never use human waste compost in a garden, so making compost would just be the result of this waste particular elimination method...not for practical use in my situation. For this reason an incinerator unit is preferable to an SCU for me.
Incinerator units are the same size and cost the saem as SCU's. Also, the SCU's I read up on that I might use would have a powered fan running 24/7 or especially while in use so the use of electricity is not an issue for me. I did not like any of the "non-powered" units I read up on.
If there are no other options for houses without basements (aside from manually removing the waste and dumping it into a composter), and considering my distaste at the idea of using human waste compost in a garden, I would simply opt for the equally priced/size incinerator unit.
Response to Benjamin Gunnells
An incinerating toilet would be probably the last choice for anyone interested in building a green home or saving energy. They use a lot of energy because first they have to get rid of all the liquid and then incinerate the remaining solid. Not a wise choice at all, in my opinion.
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