Conserve Water with Compost Toilets
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. Compost toilets are designed with this concept in mind.
Earth Closet - 1875
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. Humans infuse the soil with animal wastes to feed the same natural process, resulting in healthier growth of plants and crops.
Human wastes can be just as valuable used in the same way, and have been for centuries in countries like Pakistan (the Hunzas), China, India, and Peru, among others - countries that we in the west have called "undeveloped." Now we're learning lessons from them - examining the procedures they use to try to enhance our own.
Our first compost toilet designs in the West were developed in the late 1800s. Now we have several manufactured styles to choose from, all of which process human waste into rich, odor free fertilizer called "humanure" and help us save water in the process.
Compost Toilet 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 compost toilet, you would automatically cut your water bill down by 1/3 without doing anything else.
"The function of all organic matter, animal and vegetable, is to maintain the fertility of the soil" -- J.C. Wylie, "The Wastes of Civilization"
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 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) compost toilets are much simpler. You excrete your wastes, which are transported to a compost container (or "eco-bin") where they are turned into a rich soil amendment by microbes.
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 Compost 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, and mounted on a carousel that rotates when one container is full and needs replacing with an empty one.
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.
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 transport the humanure to the landscape periodically. It takes about six months for a full bucket of wastes to be converted without a heater.
Benefits of Compost 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 greywater system you install - no need to modify your greywater 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 in locations where there is no sewage system - Works as well for farms, cabins, yurts, and boats as it does houses in the city.
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 compost 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 compost toilet. The inn's website shows photos of the setup and décor, along with diagrams of how the toilet works. See link below.
Pit Toilets & Smell
Note that compost 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 weather, hot or cold. It's the perfect breeding ground for bacteria and pathogens, whose functions are what produces the smell.
In compost toilets the liquids are either separated from the beginning, or quickly evaporated via air flow, fans, and/or a heater, so the residue is fairly dry. Pathogens are killed off from the heat of the dry wastes composting. What little odor remains, if any, is vented outside.
A Sustainable Bathroom Includes a Compost 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 will need to be disposed of in a different way.
Compost Toilet Maintenance
Ongoing - Depending on the make of toilet you have, you may need to throw a handful of compost 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 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, agricultural fields).
Features & Price Comparison
For comparison, here are the lowest and highest-end compost 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 compost 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 compost 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 Toilet
Amazon.com - Carries Nature's Head and SunMar Excel compost toilets.
eBay.com - 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.
There are no regulations for quality control standards of manufactured compost 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 compost toilets, because there is no black water when the composting process has finished. Check here to see if there are restrictions in your state (if you live in the U.S.):
Toilets of the Future
Compost 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.
More information on compost toilets:
- Ecological Conservation at the lodge | Black Sheep Inn
The Black Sheep Inn, Ecuador, is an ECO Retreat and Permaculture Demonstration Site. We practice sustainable agriculture, recycling, composting, dry toilet use, and other such eco-practices.
- Compost Toilets: Practical Answers | Practical Action
This technical brief describes how to build a compost toilet that has proven to be most effective in water-logged areas, where pit-latrines and septic tanks are inappropriate.
- Humanure: Journey to Forever organic garden
Wastewater treatment is much more energy-intensive than composting, which is why the future may hold more old-school commodes in store.