I would consider this post as advertising, something I would have thought was not permitted on these pages.
Ross

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Comment by moderator (EvM):
Geoff's post is deemed to be acceptable, see also here: forum.susana.org/241-composting-toilets-...let-a-misnomer#27525 and here: forum.susana.org/39-miscellaneous-any-ot...-allow-on-this-forum

During my Phd on the topic of waterless human waste management at the University of British Columbia (Vancouver BC) I studied for 3 years on composting toilet performance. I sampled waste from dozens of conventional (mixed waste + wood bulking agent) composting toilet units of all manufacturers in North America, including Phoenix, Sun Mar, Clivus, and others. ZERO of them produced anything that resembled compost or fit the definition of compost. Some of the units were installed in fully insulated and heated buildings like the CKChoi building, which was operated by trained and dedicated personnel. Material was too wet, not stabilized, had high ammonia, brewed pathogens, and looked and smelled like raw waste.

The peer reviewed paper is published in Journal of Environmental Management.
www.ncbi.nlm.nih.gov/pubmed/23435183

If anyone has data to show that a composting toilet makes compost, I'd be excited to see it and review it. Here is the data that is necessary to prove that a composting toilet makes compost
1: needs to have a documented thermophilic step to kill pathogens (temp sensor record) along with indicator testing (E.coli). In the absence of a proven pathogen reduction step such as temperature, the material would need to be tested for the full suite of potential pathogens including hook worm ova viability, enteric viruses, as well as the usual E.coli. E.coli testing on its own, in the absence of temperature monitoring shows very little in the way of true pathogen risk.
2: needs to be well stabilized (i.e. high Solvita value like >5 or such)
3: needs to have a low ammonia value and some nitrate should be found in the material
4: should not have offensive odors
5: should not have big turd looking shapes in it

In order to make compost there needs to be a thermophilic stage. Never in documented literature has a composting toilet (box below a poop hole) has a toilet waste pile been found to achieve thermophilic temperatures (or really anything greater than 10C over ambient). Moreover, there are a half dozen other biochemical and design reasons why these units will never make compost including: A) short circuiting due to leachate seeping through fresh turds on the top of the pile into the bottom 'finished' zone within a few hours; B ) excess ammonia from urination preventing biological activity (the ammonia levels in most 'composting' toilets was so high that it killed nearly all life, and was almost a viable pathogen destruction method - I joking called these toilets 'toxification toilets' instead of composting toilets).

Lets not propagate inappropriate terminology. Composting toilets don't make compost. Lets call them waterless toilets or dry toilets. Compost is a special term for a material that is safe, stable, and beneficial. The material that emerges from composting toilet chambers below poo holes does not (and I daresay cannot) produce material that meets these important safety concerns.

If we continue to call composting toilets "composting toilets" we do so in the face of science at the continued risk of human health impacts due to the perception that the end-product is actually compost, a safe, stable, and beneficial substance.

We should be focusing on reclaiming nutrients from diverted urine, which self sanitize in batch storage, have 10x the nutrient value by weight compared to feces, no heavy metals, and flows by gravity. Urine diverted feces can be fed to bugs, minimized, rarely touched by humans, and post-treated with urea and or ash, for final pathogen destruction of the well stabilized 10+ year old material, prior to trash removal (screening) and subsequent land application.

Following this ethos, ToiletTech has implemented 200+ urine diverting toilet solutions at some of North America's highest use public back-country sites including Zion's Angels Landing, Whistler Canada, Mt Rainier Washington, Longs Peak Colorado, Smith Rocks State Park Oregon. Our toilets at these sites are visited hundreds to thousands of times per day. Many of these sites had failing composting toilets or evaporating toilets. Our systems reduce the operator costs to 1/5th of the original and result in very small residual waste to be managed / removed / pontificated about. Happy to share references to operators in the National Park, Forest Service, and State Park for those trying to figure out how to manage waste at high use sites.

You did not mention the use to which you will be putting the composting toilet. The options will vary depending on number of users, location, and building design. Also availability of a safe and dedicated space for the secondary composting if you use any of the units you listed.

I agree with Geoff Hill that the smaller composting toilets are misnamed and it is misleading to call them composting toilets. One can argue that they do facilitate composting because they make the resources available rather than flushing, burying, or incinerating them, but you would need to physically transport your contributions to a sequestering bin or dedicated compost pile. Depending on number of users, this can become a tedious and unpleasant task. My experiences allow me to disagree with him about in-vessel composting though.

There are other larger, but more expensive options that successfully compost in-vessel, but require a space for a larger container in a basement or equivalent space below the bathroom. Phoenix Composting Toilets are the system I prefer. www.compostingtoilet.com Clivus Multrum, Sun Mar Centrex, are others. The Full Circle Composting Toilet is a UD batch toilet similar to the Separett but with a larger below-floor interchangeable containment vessel.

One thing to keep in mind is that the smaller the toilet and the lower the price will be inversely proportional to the amount of maintenance required for successful operation of the unit. Also, the more direct and intimate contact you will have with its contents. Batch systems such as Separett or Full Circle, require some maintenance, but it is much less objectionable than the potential for carrying open containers of sewage.

The larger “below-floor” systems have a much longer retention time in vessel. Systems like Phoenix, for example, have a multiple year retention time and assure that any material removed is the oldest. I disagree with Geoff that composting cannot take place in-vessel.

Some of the “same-floor”models require that you use a proprietary aka expensive “composting” formula to add to your contributions. This adds an ongoing cost which is not insignificant, when added to the cost of the electrical use for fans and heaters.

Of the ones on your list, I urge you to consider the Separett.

Composting toilets do not make compost. Do not be fooled by the advertisements. My peer reviewed papers on available on this topic. Additional ones can be found in the literature.

There are mixed waste dry toilets (waterless) and urine diverting dry toilets (also waterless). Neither make compost. The definition of compost is a material that has been thermophilically and mesophilically treated to reduce pathogens by 4 logs. Neither mixed waste nor urine diverting dry toilets achieve this without additional efforts. Both can be batch mixed with proper amendments at the right scale (>1 ton) to make thermophilic composting happen. Stabilized urine diverted dry waste (by means of invertebrates or other biological means) can be post treated with urea and ash. Research work by Nordin on this topic.

Waterless toilets are an important aspect of human waste management all over the world, but we all need to be clear on what is false advertising and what is the true value. Composting toilets do not make compost. They do provide a receptable which collects pee and poo (mixed waste) or just poo (urine diverting). Mixed waste toilets have excessively high ammonia in the sludge, regardless of bulking agent. Urine diverted solid waste can be consumed by invertebrates (which are sensitive to ammonia levels).

www.researchgate.net/publication/2357166...zing_the_end-product

www.semanticscholar.org/paper/Vermicompo...9b5e47bbc87e142e3294

www.researchgate.net/publication/2603908...Helminthic_Parasites

Definition of compost per USCC
wasteadvantagemag.com/uscc-efforts-resul...by-regulators-group/