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Conserve Water with Composting Toilets

Updated on May 26, 2019
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With a master's in sustainable development, Susette helps Southern California water agencies carry out their water conservation projects.

Nature's way of dealing with "wastes" is to use and reuse and reuse a thing, until there is nothing left. Each reuse contributes to the growth of something else, so there is no real waste. Composting toilets are designed with this concept in mind.

Earth Closet—1875

Earliest advertisement found so far for compost toilets in the West.
Earliest advertisement found so far for compost toilets in the West. | Source

In nature, mycelium (mushrooms) grow when they break down petroleum contaminants into components edible by soil microbes. Soil microbes grow when they break down what the mushrooms left, and plants grow on the wastes of the microbes.

In some countries—like Pakistan (the Hunzas), China, India, and Peru—farmers infuse the soil with human wastes to feed the same natural process, resulting in healthier growth of plants and crops. Now we are learning lessons from them, by examining the procedures they use to help us design composting toilets.

The first composting toilet designs in the West were developed in the late 1800s. Several manufactured styles exist now, all of which process human waste into rich, odor free fertilizer called "humanure" while helping us save water in the process.

"The function of all organic matter, animal and vegetable, is to maintain the fertility of the soil."

—J.C. Wylie, "The Wastes of Civilization"

Potential Water Savings

According to the Renewable Energy Center in the United Kingdom, 1/3 of domestic water use is for flushing toilets. If all of those toilet flushes were to come from water already used for something else (greywater) or if you were to install the kind of toilet that doesn't use water at all, like a composting toilet, you would automatically cut your water bill down by 1/3 without doing anything else.

"Wet" toilet in a public restroom in the U.S. shows where flush water is supplied through pipes in the wall.
"Wet" toilet in a public restroom in the U.S. shows where flush water is supplied through pipes in the wall. | Source

Wet Toilets vs. Dry Toilets

Wet toilets use water to flush. The tank above the seat contains a couple of gallons of drinking water. When you depress the handle, that water flows down into the bowl to wash out everything you just dropped into it (including toilet paper).

The flush water and all your wastes flow through pipes into an extensive underground system that flows into bigger pipes and bigger ones, as household pipes join them from all over the city. Then all the sewage flows into a massive, centralized treatment plant that filters out contaminants, and treats the remainder with chemicals prior to sending it out to "leach fields" to sink slowly into the earth.

Dry (waterless) composting toilets are much simpler. You excrete your wastes, which are transported to a composting container (or "eco-bin") where microbes turn them into a rich soil amendment.

No need for an extended, underground piping system spidering across the city, or a huge, billion dollar treatment plant. No need, either, for the ongoing millions of dollars spent on chemicals to destroy what was once a valuable potential soil additive.

Types of Composting or Eco-Toilets

There are a wide variety of eco-toilets being manufactured today or being created by do it yourselfers (DIY). Most of them use one of four main methods:

  • Self-contained—where the toilet and composting container are one unit, with a removable tray that can be emptied onto an outdoor compost pile when full.

  • Remote—where the toilet is located separately from the composting site. This is sometimes an open-air system, planted with trees and nettles around it that use the compost, so there is no container that needs emptying.

  • Batch—where waste is collected and composted in two or more sealed containers mounted on a carousel that rotates when one container is full and needs replacing.

  • Continual process—where waste is composted slowly in a single container, and compost is harvested from the bottom on an ongoing basis.

More recent designs actually separate liquids from solids as you deposit them. The liquids go into a separate collection system, where they are diluted with water and can be used immediately to fertilize the soil. The solids drop into the eco-bin, where they are cooked to kill pathogens (desiccated), or mixed with a composting material like sawdust, which heats up during the microbial ingestion and also kills pathogens . . . just slower than the desiccator kind.

Composting Toilet Diagram

Person sits on seat (level A) and liquids are diverted through (4) into their own container (5), while solids drop down through (3) into the container below (1). The air vent (2) releases any odor to the outside.
Person sits on seat (level A) and liquids are diverted through (4) into their own container (5), while solids drop down through (3) into the container below (1). The air vent (2) releases any odor to the outside. | Source

Once dried, the compost falls apart (humanure) and is ready to be distributed. The humanure from one remote type automatically rolls down onto the soil when it's ready, however most styles require someone to periodically transport the humanure to the landscape. It takes about six months for a full bucket of wastes to be converted without a heater.

Benefits of Composting Toilets

There are several benefits to installing dry toilets, in addition to reducing the amount of water used:

  • Provides good fertilizer for the landscape. With these toilets it's an easy thing to convert body wastes to fertilizer.
  • Reduces demand on your town's water supply system. Doesn't use water, which means there's more available for others who need it, and less to transport long distances.
  • Supplements any grey water system you install. No need to modify your grey water system to supply water for flushing—you can send all of it out to the yard.
  • Reduces groundwater contamination. No septic systems or sewage pipelines to leak raw, contaminated sewage into the ground.

  • Saves cities and counties money. No need for installation of septic tanks or costly sewage treatment plants.

  • No mosquitoes or smells. Compost containers are closed, dry systems not useful to mosquitoes for breeding or the bacteria that create the odors.

  • Can be installed where there is no sewage system. Works as well for farms, cabins, yurts, and boats where there is no existing sewage system, as it does houses in the city.

Composting Toilet Installed in a Bathroom

Self-contained composting system by one of the first manufacturers of such systems in North America.
Self-contained composting system by one of the first manufacturers of such systems in North America. | Source

Sweden is using compost toilets in roadside facilities, and the U.S. and U.K. are both using them in national parks, where there are not enough water or septic tanks to use the more common wet toilets.

Eco-tourism facilities in remote areas worldwide are building composting toilets into their guest rooms. The Black Sheep Inn in Ecuador is a beautiful example - they added plate glass windows to their bathrooms to allow guests a mountain view while using the composting toilet. The inn's website shows photos of the setup and décor, along with diagrams of how the toilet works. (See link below.)

Composting toilet in a public restroom in Sweden. Note that any drugs a person has taken are burned off in this kind of system.
Composting toilet in a public restroom in Sweden. Note that any drugs a person has taken are burned off in this kind of system. | Source

Pit Toilets and Smells

Note that composting toilets are NOT THE SAME as pit toilets. Pit toilets are the ones you can smell a mile away, as you approach a picnic camping area after a long hike in the woods. What makes them smell is the mixture of liquids and solids in a deep pit that sits there forever in hot or cold weather. It's the perfect breeding ground for bacteria and pathogens that produce the smell.

Composting toilets either separate the liquids at the beginning, or quickly evaporate them via air flow—fans and/or a heater—so the residue is fairly dry. The heat of the dry, composting wastes kills off pathogens, while vents direct any remaining odor outside.

A Fully Sustainable Bathroom Includes a Composting Toilet

"Contrary to popular opinion, compost toilets can be very clean and do not smell."

- Technical Brief, Practical Action

Toilet Paper & Other Disposables

Since the whole purpose of a composting toilet is to have everything in it decompose, it makes sense to only put things into it that can decompose. Toilet paper is made to break down in septic tanks, so it will be OK in a composting toilet. However, sanitary napkins and diapers will not break down. Those need to be disposed of in a different way.

Composting Toilet Maintenance

Ongoing—Depending on the make of toilet you have, you may need to throw a handful of composting mix into the eco-bin every time you use the toilet. You will also need to turn a handle or push a button to mix the humanure every time you use it or every couple of days.

Periodic—Wipe down outside as you would a wet toilet. Clean out the urine container (if present). Empty the eco-bin when it gets full or take humanure out from the bottom to leave room for more. If you empty it out fully, it's OK to leave a little in the bin. Like anything involving microbes, leaving a sample population behind starts the next batch (e.g. kombucha, sourdough bread).

Features & Price Comparison

For comparison, here are the lowest and highest-end composting toilets I could find. Those in between have a variety of features, based on the brand. Be sure to check reviews before buying.

Full Service System—Envirolet's FlushSmart VF800, $5,000 regular price

This is a mini-flush remote composting toilet that uses one glass of water per flush, combined with an air vacuum, to transport wastes to a separate location. The location can be above or below the toilet up to 20 feet away. Included with the system are:

  • Starter kit (compost material and microbes) for 2 starts
  • Sample bag of daily compost mix
  • 16 foot drain hose and connecting equipment
  • Wind turbine ventilator with two fans
  • Automatically aerates and pulverizes the wastes for quicker decomposition
  • Uses polymer plastic that will not collect odors
  • Capacity is 10 people per day part time or 8 people fulltime
  • Lifetime warranty on body, 5 years on internal components

Basic System—Nature's Head, $910 plus any accessories you wish to supplement it with.

This is a simple system designed by two long-time sailors wanting something durable for their boat. It works well for any facility that is off-grid. The toilet sits on top of the composting bin in this self-contained unit. It requires a couple of hand cranks every time you sit down to help the compost mix, and hand emptying when the bucket or urine bottle is full.

  • Hank cranked
  • Separate urine collector
  • Housing for computer-type fan to help with aeration
  • Hose and fixtures to set up an outside vent
  • 5 year warranty

You provide: Computer or similar small fan, outside air vent, composting agent (sawdust, peat moss, coconut fiber, etc.)

Extras you can purchase: Vented lid for carrying the bucket, another urine bottle, solar-powered vent, an extra compost bin.

Where to Buy a Composting Toilet—Carries Nature's Head and SunMar Excel compost toilets.—Carries Nature's Head, SunMar, and BioLet toilets for "Buy It Now" prices within $100 of the cost at Amazon.

Manufacturer—Some manufacturers, like BioLet, use private distributors and don't advertise on Amazon, although they might on eBay. Envirolet sells direct. Check the manufacturer's site first for detailed specifications and their prices, before checking either of the sites above.

Government Regulations

There are no regulations for quality control standards of manufactured composting toilets at the moment. However, most manufacturers are voluntarily meeting the same standards that wet toilets must meet—the ANSI/NSF International Standard 41, updated in 2009 to accommodate for new reduced-water toilet styles.

As far as installation is concerned, in states like California there are no regulations. Existing black water regulations do not apply to composting toilets, because there is no black water when the composting process has finished. Be sure to check to see if there are restrictions in your state (if you live in the U.S.).

Toilets of the Future

Composting toilets are an exciting new development, especially for us Back-to-Nature types. However, they are not the only new toilet designs coming up. Here are designs that are being funded for development and one (the last one) already in production:

  • Microwave toilet that transforms wastes into energy (funded by Bill Gates Fdtn).

  • Toilets that turn solid wastes into charcoal and utilize urine for flushing.

  • Solar powered toilet that generates hydrogen and electricity (CA Institute of Technology).

  • Toto's "Washlet" (a wet toilet) with heated seat, a mini powerwasher arm (adjustable temperature and pressure), a dryer, and deodorizer.

Toto's Washlet—Note the controls on the left of the photo. These make it easy to warm up the seat, and activate the washer arm and the bum dryer.
Toto's Washlet—Note the controls on the left of the photo. These make it easy to warm up the seat, and activate the washer arm and the bum dryer. | Source


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    • profile image


      6 years ago

      Wonderful article. We live in such a wasteful society. Very few people think of the value of clean drinkable water until there is some kind of disaster, like during hurricane season. I can't agree with you more, We owe it to ourselves and the planet to be better stewards of the environment.

    • watergeek profile imageAUTHOR

      Susette Horspool 

      7 years ago from Pasadena CA

      Yep. Big contrast from that earlier one in the 1800, isn't it? ;-)

    • Teresa Coppens profile image

      Teresa Coppens 

      7 years ago from Ontario, Canada

      Very interesting article. I had no idea these toilets were so advanced.

    • watergeek profile imageAUTHOR

      Susette Horspool 

      7 years ago from Pasadena CA

      "Fecophobic" - I love it! Did you make up that word? Thanks for your comment and compliment, DrMark.

    • DrMark1961 profile image

      Dr Mark 

      7 years ago from The Atlantic Rain Forest, Brazil

      What an excellent article! I mention humanure briefly in my hub about composting dog waste, but most people are so fecophobic that I did not even try to dwell on the issue. It is great to see you doing such a thorough job on the subject!!!


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