Humanure Recycling: A Composting Toilet for Garden Compost

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An organic gardener reaps the results of conscientious composting: free fertilizer. Properly composted, humanure is a safe, nutrient-rich amendment.
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Gardening using humanure.
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Diagram: Composting toilet anatomy.

Learn about how to use humanure recycling created from a composting toilet.

Composting toilets are a world away from
the odoriferous outhouses of yesteryear. And low-flush
conventional toilets offer an option for those unprepared
to recycle human manure. To save money, extend the life of
your septic system and help protect water quality, read on.
Become a water-wiser watermiser.

One person using a composting toilet can produce more than
80 pounds of compost and save more than 6,600 gallons of
water per year. While composting toilets make environmental
sense, they also can put dollars and cents back into your
pocket by reducing your water bills and extending the life
of your septic system.

Composting toilets stabilize and recycle human manure and
toilet paper without using or polluting drinking water.
Unlike flush toilets, which treat human manure as waste, a
composting toilet lets you reclaim and recycle
nutrients — using the same biological process as garden
composting piles to break down excreta, or human manure.
What’s left is nutrient-rich organic matter, or humus,
which can be used as a soil amendment.

Once considered an option only for parks, homesteaders and
seasonal cottages, composting toilet systems are turning up
in suburban residences and’ commercial buildings, often in
environmentally sensitive areas.

Composting Toilets

Commercial composting toilets first appeared in the United
States in the 1970s, as mostly just a way to avoid
installing a flush toilet and expensive septic system. But
issues of shoddy construction and overoptimistic designs
plagued both the manufactured and build-it-yourself models,
and users struggled with odors, flies, incomplete
processing and hard-to-empty systems. The legal foot came
down in the early 1980s when a report by the U.S.
Environmental Protection Agency and the California Division
of Occupational Safety and Health gave these systems
failing marks. Since then most designs have improved
significantly, reflecting a healthier respect for the
aeration and heat requirements of composting.

Many of today’s composting toilets can be used with vacuum
toilets (such as the 1 pint microflush SeaLand, originally
made for recreational vehicles and boats) and Japanese
foam-flush toilets (see Page 92 in this issue for more information). In
many states, using a composting toilet allows a property
owner to install a smaller septic system. Many owners now
opt for service contracts to maintain their composting
toilet systems.

Care and Feeding of Humanure in Composting Toilets

Composting relies on aerobic (oxygen-loving) bacteria that
work 10 to 20 times faster than the anaerobic (oxygenless)
bacteria at work in septic tanks. The challenge of
composting toilets is getting air to the composting process
while minimizing human exposure to the contents. That calls
for careful engineering of airflow, so air is taken in and
then exhausted through the exhaust vent chimney, not
through the bathroom.

Some management is also required: turning or batching the
material, and adding coarse material (such as sawdust or
dry leaves) to keep it porous, so the aerobic bacteria stay
healthy and functional.

Keeping the material aerated also means it can’t be too
wet, so only waterless or microflush toilets are used with
composting toilet systems. Waterless toilets are usually
just toilet stools with 8- or 10-inch openings that connect
through a straight pipe into the composter. For those who
want a toilet trap between themselves and the composter, a
microflush toilet, such as the SeaLand Traveler 1-pint
flush toilet, can be used, provided extra liquid in the
composter is evaporated, drained to a septic system or used
in subsurface irrigation. Other microflush toilets include
foam-flush toilets, which use an aquarium-type air pump to
bubble air through a soap-and-water mixture, creating lots
of foam to move material out of the bowl.

Composting toilet systems are not a flush-and-forget
technology. They require consciousness of what’s put into
the toilet (No toxic chemicals, please!), some maintenance,
well thought out siting and installation, and in many
cases, electricity for operating fans and heaters.

The most common installation mistakes are siting them in
cold places (unheated basements, for example), not draining
away leachate (liquids) and installing systems that are too
small for the usage they’ll get.

Humanure: Using the End Product

In composting toilet systems, most pathogens are destroyed
through a combination of heat and retention time. But many
states require the compost toilet end product either to be
hauled off by a sewage hauler or buried under 6 inches of
soil. To comply and still reap the nutrient benefits of
human manure, most folks choose to bury the end product in
the root zone of ornamental plants. Even without legal
approval, some individuals choose to compost the end
product further in an active, outdoor compost pile, or to
use a pasteurizer, such as a solar oven, to destroy
potential pathogens.

Will Brinton, Ph.D., of Woods End Research Laboratory has
tested several samples from composting toilets in the past
year. Most of the samples have undergone at least 1 1/2
years of retention time. “In all the samples of composted
human manure we have tested, E. coli pathogens were not
present at levels relevant to the Environmental Protection
Agency’s pathogen test rule,” says Brinton. “Adequate
composting time and/or temperatures generally will make
human manure safe to use, even though local laws may not
acknowledge this fact. We recommend individuals who wish to
use composted human manure for surface application test for
fecal coliform after the first round of composting.” [For
details, contact Woods End at]

Types of Composting Toilets

There are several types of composting toilets. These
systems are either self-contained (usually for cottages) or
central (also referred to as remote and
below-floor ).

With self-contained systems, the toilet
seat and a small composter are all one unit. Due to their
small size, they are typically used in cottages and
seasonal homes. Because of their limited capacity, these
systems require frequent emptying, which is accomplished
simply by removing the small tray that sits underneath the
toilet. The end product from these systems can be buried
around trees and shrubs, or composted with other materials
in an outdoor composting bin. Prices range from about $750
to 1,500 for these units. Self-contained systems include
models available from Sun-Mar, Biolet and Envirolet.

In a central system, the toilet empties
to a separate composting chamber, usually located in the
basement or in its own enclosure to the side of the
building. In these systems, frequent emptying is not
necessary, although you may need to rake the contents
occasionally. When the chamber fills (usually within a
year), the contents — which have composed into a fine,
crumbly product — can be removed with a shovel and
wheelbarrowed out to an outdoor composting bin or buried in
trenches outside. Commonly the choice of year-round homes
and facilities with multiple toilets, central composting
toilets range in price from $1,400 to more than $10,000 for
large-capacity systems. Systems include AlasCan, Clivus
Multrum, CTS, EcoTech Carousel, Phoenix and Sun-Mar

Do It Yourself Toilet Systems

Many homeowners make their own systems. Some designs are
simply copies of manufactured systems, such as a concrete
version of sloped, single-chamber systems like the Clivus
Minimus. Other designs use a batch
with two or more interchangeable
containers: When one fills, another is put into use,
allowing the first container to process without fresh
inputs. The containers are either fixed, as in aerated
twin-bin systems made of concrete (CEPP Net Twin-Bin,
Farallones System, Gap Mountain), or they are alternating
containers, such as barrels and rollaway trash bins (CEPP
NetBarrel, Sol-Latrine, Sunny John). The best designs
feature some kind of management of the leachate and
adequate ventilation for the composting process and odors
(both the books listed in “On the Bookshelf,” page 91 of this issue, give
detailed information on batch systems). All of these
systems can be used with microflush toilets. The CEPP
NetBarrel system, which can be integrated with a graywater
system, can cost as little as $15 to construct. Add a
1-pint flush toilet, and the total is only $260. These
systems provide as much capacity as one has

Some users bypass composting toilets altogether and use a
very low-tech system, collecting their human manure in a
bucket housed underneath a small built-in cabinet. With a
standard toilet seat and lid on a hinged top, the cabinet
hides the bucket until it’s ready to be emptied. A cover
material, such as well-rotted sawdust or finely ground
leaves, is added after each use to act as an odor filter.
When the bucket is full, it’s emptied into an outdoor
composting pile. Distinguished from composting toilets, in
which composting takes place within the chamber itself,
these sawdust toilets are simple
collection devices; the actual composting occurs along with
veggie peels, grass clippings and other compostables in a
separate, outdoor bin. Direct outdoor composting requires
no fans or electricity, but does require management and
lots of carbon-containing cover material (sawdust, rotted
leaves and straw) to cover the manure for composting.

This method probably won’t gain approval from most health
officials as a replacement for a flush toilet. Sawdust
toilets are for people who are serious about nutrient
recycling, don’t mind the regular job of emptying
containers onto a compost pile and will responsibly manage
the compost to ensure the compost pile achieves
thermophilic conditions (more than 113 degrees) to destroy
pathogens. Because his compost achieves high temperatures
and undergoes two seasons of aging, organic gardener Joseph
Jenkins uses his composted human manure as a garden soil
amendment. In most other composting toilet systems,
although some excreta breakdown occurs within the indoor
chamber, materials usually do not heat up enough to
reliably destroy pathogens. To comply with legal
regulations, most manufacturers advise against using the
end product in food gardens. Jenkins details the
differences between sawdust collection systems and
composting toilet systems in his book, The Humanure
(See MOTHER’S Bookshelf, page 103 in this issue).
Instructions for building a sawdust collection toilet can
be found at

The Current Laws

Plumbing and wastewater codes usually allow composting
toilets when a conventional septic system or sewer service
is already in place. For all other situations, property
owners may have to get special permits, depending on the
state. Maine, Massachusetts, Minnesota, New Mexico and
Washington are among the most accepting. Although National
Sanitation Foundation listed systems are preferred, many
states also approve systems based on their own criteria.
New onsite standards, which may be adopted nationally, will
likely approve any model that features the capacity for
two-year retention of the end product. Given enough
information about the systems, most health officials are
usually willing to work with homeowners. Legal acceptance
of composting toilets is increasing rapidly, as their
benefits become clear to all: no pollution, water and
energy savings, and nutrient recycling.

Low-Flush Toilets

For those of us who live in areas where composting toilets
aren’t permissible yet, an alternative to water-wasting,
high-volume toilets is low-flush toilets. If you are
planning to build a home, federal law now requires
1.6-gallon low-flush toilets be installed. Older toilets
suck down between 3 to 5 gallons of fresh water with each

According to the American Water Works Association (AWWA),
the average American uses 74 gallons of water per day.
Almost one-third of this water goes to flushing toilets.
Seem wasteful? It is.

As demand for pure water grows while fresh water supplies
dwindle, conservation measures must be implemented. A
1.6-gallon low-flush toilet can cut household water usage
by 20 percent or more. The AWWA estimates if every American
household switched to water-efficient toilets 22.3 million
gallons of water would be saved each year.

So what’s the holdup? Unfortunately, these watermisers
weren’t designed well when they were introduced. Folks
frequently faced the fate of double-flushing or, even
worse, clogged toilets. “Back when the lowflush models were
first mandated in 1992, the imported Swedish lowflush
toilets worked great,” says David Del Porto, a designer of
water conservation and alternative wastewater systems. “But
U.S. manufacturers didn’t change their designs. They just
made smaller tanks.” Coupled with old pipes and low
pressure in many older homes, the first U.S. lowflush
toilets were doomed to fail.

Now changes in design have produced high-performing
low-flush toilets that can significantly reduce your home
water use and take a load off your septic system.

“Today’s 1.6-gallon toilets — even the mediocre
ones — are a lot better than the old 5-gallon flush
toilets,” says plumber Terry Love, who has sold and
installed low-flush toilets since 1974.

Love says the biggest problem is clogging. Some toilets
have sharp edges in their drains that catch toilet tissue
as well as items people drop in toilets, such as makeup
pencils, pens and toys. For that reason, shop for toilets
with smoother edges around the drain and more sweeping
traps with gently angled drains. They simply perform
better. (Toto and most high-end models qualify; see Love’s
recommendations on page 92 in this issue).

Types of Low-Flush Toilets

Gravity-flush toilets are the most common,
have the simplest design and are usually the least
expensive, ranging in price from $50 to $420. When the
toilet knob is pressed, a flush valve opens, and the water
in the toilet tank drains into the bowl through rim
openings. The force of the water pushes the waste through
the trap and down the drain line. While they are less
effective at removing solid waste than pressure-assisted
toilets, they’re generally less expensive and easier to
maintain, since most use standard, widely available parts.

Pressure-assisted toilets are suited for
commercial buildings or in homes with poor drain line
carry, where pipes aren’t pitched enough to allow waste to
flow easily to the septic system or sewer line. When the
toilet is flushed, the pressure of the water coming into
the main tank compresses air in an inner tank, forcing
water into the bowl and blasting waste down the drain. Some
consider pressure-assisted toilets noisy, although Love
says the whoosh of a pressure-assist is just
unfamiliar compared to the gurgle of a gravity-flush
toilet; Pressure-assisted toilets are more effective in
removing solid waste and limiting odor and soil problems,
but are also a bit more expensive than gravity-tank
toilets; prices usually start around $230.

Perhaps the greatest advance in water-saving toilets are
the dual-flush toilets, which feature two
flush buttons: Press the dark one to flush feces with 1.6
gallons of water or press the light one to flush only urine
with 8 gallon. Caroma’s dual-flush from Australia is now
imported to the United States; prices start at $250.

Vacuum toilets use a vacuum pump to suck
waste away. They are expensive and mostly found in ships,
trains or buildings where waste must be moved without the
benefit of gravity. The Seal-and microflush 1-pint toilet
is one of a few toilets made for boats and recreational
vehicles, and for use in composting toilet systems. These
toilets can transport waste a long distance.

Toilet Tips

Before installing a low-flush toilet, check to make sure
your drain system is working and does not block easily. If
your drain system often clogs, have it fixed, but also
specify a toilet that is rated high for drain line carry.
If your home was built within the last 10 years, any of the
low-flush toilets will work.

Love’s website ( describes
his favorite low-flush toilets. His first choice? The
UltraMax, a gravity-flush by Toto. “It is a good-looking
one-piece that incorporates a 3-inch flush valve, instead
of the standard 2-inch, which allows the waste to drop
quicker. It meets commercial requirements, works well in a
home and is quieter than the pressure-assisted models.” He
says the only drawback may be less bowl wash. Priced around
$350, its a little more expensive than some toilets, but he
thinks it’s worth the money.

For low-use applications, Love recommends pressure-assisted
Gerber models ($9) to $279), and the gravity-flush American
Standard Cadet ($174) or Western Aris ($99).

The economics of flushing with less is apparent: A New York
City program that offers subsidized or free low-flush
toilets in exchange for property owners’ 3- and 5-gallon
toilets has saved millions of dollars in water costs since
1992. Nationally, the new low-flush toilets are credited
with saving between 25 and 60 gallons of water per day
each, saving consumers an estimated $50 to $100 on their
annual water bills.

“Today’s low-flush toilets work,” Love says. “And these
days, we just don’t have the water to waste.”

Carol Steinfeld is the co-author of  The Composting
Toilet System Book. Claire Anderson contributed
research to
The Humanure Handbook and is an
assistant editor at MOTHER EARTH NEWS.

Composting Toilet Sources




Clivus Multrum

CTS Composting Toilet

EcoTech Carousel

Envirolet Composting Toilet

Phoenix Composting Toilet

Sun-Mar Corporation

Composting Toilet Anatomy

The technology varies, but the typical components of a composting toilet system include:

1. A waterless toilet stool or a microflush toilet;
2. A composting chamber, where one or more dry or microflush toilets empty;
3. A screened ventilation inlet ;
4. An exhaust system, often fan-forced, to remove odors, carbon dioxide and water vapor; and
5. An access door (5) to remove the end product.

(See the composting toilet anatomy diagram in the image gallery.)

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