We Get Greener Kit Cassingham & her Bigger Half

Composting Toilets

Ready to go waterless with your toilet? I'm not talking about waterless urinals, though that's a distinct option. I'm talking about composting toilets.

In 1992 the US government required that toilets be more water efficient; no more five gallons per flush could be sold. Pressure assist and low-flush toilets replaced the water hogs. Then came dual flush toilets.

Composting toilets have been around a long time, but haven't been used in many homes or offices because of their various constraints -- smell, waste disposal, acceptability. But, as with so many things, the technology has improved enough that not only can they be used indoors comfortably, but they are being used indoors.

Composting Toilet Models
Composting Toilet With Individual Holding Pan
Remote-Tank Composting Toilet

Do you know what a composting toilet is? It's not the same as a latrine or an outhouse. It is a device that processes human excrement through aerobic processing, and with proper ventilation, to create decomposed, odorless matter that's 10-30 percent of its original volume. You can choose from self-contained and central (or remote) units. I'll cover more of the system works in a moment.

I was intrigued with the composting toilets on Longs Peak, Rocky Mountain National Park, CO, as a young adult. They are located just below the Keyhole, at the top of the Boulder Field, the last chance to "de-fuel" comfortably before the push to the top. The waste was dried with solar panels "cooking" the deposits, which were then packed down the mountain by pack animals at the end of the season. What a great way to protect that fragile environment. And what a pleasant way to "de-fuel".

When My Bigger Half and I started designing our new home in 2002, a friend pointed us to a "new" dual flush toilet. The concept was new to me, though evidently Caroma has been selling dual-flush toilets in Australia for a long time. We liked what we saw -- literally; it was demonstrated by a plumbing store in Denver. We bought four of them: one for the yurt we lived in as the house was being built, and three for the house. Feel free to read the article I wrote about dual flush -- or ultra low-flush toilets, to better understand them.

But what's this about no-flushing toilets that I'm talking about now? It's about options and progress, reducing ground water pollution, and major water conservation measures.

I did research the idea of using a composting toilet in the yurt as a way of conserving water and being greener. Ultimately the concept was rejected because at that time a lot of effort was required to keep them working well, and not stinking indoors. Heck, we already had cats to help in that department, we didn't need any more ways of adding aroma! We travel just enough that the regular maintenance required to keep them working properly would be an issue, I felt. When I'm not sold on the effort required to properly maintain a system you can imagine it's hard to sell My Bigger Half on the system.

But recently I started seeing articles about the "new" composting toilets and how homeowners were installing them in middle-America homes and office buildings. They've been a fixture (no pun intended) in Europe for a long time. Natural Home magazine says this is the fastest growing trend in green building. What a radical concept! I had to investigate. Maybe we'd be using this in our next home.

What's different now from several years ago? Why do I think we can deal with this different approach to our toilet needs? I think it's the development of the central unit that has made the difference to me. A central holding tank allows multiple toilets to make deposits. There are at least two bins, one for daily use and one for composting or processing the waste; that reduces contact with partially processed excrement. They can be fully automated now, so no more bulk additions (addition of straw, leaves, or grass clippings to create air pockets for better composting). You can select models that require a bit of electricity, but that can be supplied with solar or battery power. Moisture is an important aspect to some of the systems -- for proper curing and aerobic processing; either urine or water can provide that moisture. The collecting unit can be located in the basement, a crawl space, or outdoors.

While these units are more expensive than even an expensive flush toilet, ultimately they are much cheaper. I saw prices of up to $2,500 for a multi-chamber remote system and one toilet (additional toilets are extra). But that still saves you the cost of a connection to the sewer or installing a septic system with leach field and holding tank. If you go with a waterless system you also don't have the cost of bringing water piping to each toilet (or the sewage away from each toilet), or the cost of the water for every flush. Since toilets are credited for comprising about one quarter of a home's water use, that becomes a handsome savings quickly.

Self-contained units are also options, but given our lifestyle I don't anticipate that an option. But you might. Whichever style you select, be sure to look for a toilet system that conforms to American National Standards Institute's (ANSI) composting toilets standards.

The central-unit brands I repeatedly saw during my research include:

The other thing that caught my attention with the "new" composting toilets was that commercial buildings are even starting to install them. The University of British Columbia's CK Choi Building installed five Clivus Multrum central units, serving 300 employees with 12 toilets. And the Institute of Asian Research, in Vancouver, BC, Canada, isn't even connected to the city's sewer system. It instead went with composting toilets and urinals -- in a 30,000 square foot office complex -- and a greywater system for handling water from sinks and water fountains where the water irrigates the landscape which cleans the water. Cool!

My Bigger Half and I already conserve water well, typically using less than 1,000 gallons/month -- even with my greenhouse. Water savings isn't the focus here, though it's important to us. It's more about not polluting ground water and for disturbing the land the very least we can. We'll still pay the water company as if we are using 2,000 gallons/month. We just won't have a 750-ish square foot leach field marring the land, or a holding tank to deal with.

I enjoy striving to be greener by the day. We look for new ways to get greener. Opting for composting toilets in the next house and office may be one way we can do that. Go green! Go waterless.


Kit, see attached link City of Tulsa Sludge - pdf my son, Shawn spearheaded this effort for Ardmore. This is your toilet on a grand scale.

tommy geurin at November 28, 2010 8:39 PM

Nicholas Kristof had a nice piece in the NYTimes about an organization using composting toilets in Haiti both to help with sanitation but also to help restore top soil in depleted agricultural areas. Take a look at OurSoil.org.

Fern Culhane at December 2, 2010 8:50 PM

Fern, that's a great example of the wisdom behind composting toilets.

On a less-pleasing note, when I was in China in 1996, visiting Guilin opened my eyes to their way of maintaining soil fertility. They positioned their latrines in the community garden so that human deposits became part of the garden. As they irrigated the waste was distributed. The garden smelled awful, but they had beautiful produce.

In the rice paddies some gardeners put fish into the fields. The fish eat bugs and fertilize as they go. When the rice is harvested, so are the fish. This isn't exactly the same thing as a composting toilet, but it shows how clever people can be in maintaining good soil fertility, and not wasting water to flush human waste away to be dealt with in someone else's "backyard".


Kit Cassingham at December 6, 2010 6:34 PM


It amazes me to see this kind of project going on with cities and towns across the US. Thanks for sharing this one. I hope to meet your son some day and discuss the project's success.


Kit Cassingham at December 6, 2010 6:55 PM
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