-Barrel Composting Toilet
For the past 5 years we have been developing a composting toilet design
that is simple, inexpensive and easy to replicate, yet also meets most
of the design considerations addressed on our
Regulations page. The system is constructed of 5 gallon buckets
and 55 gallon plastic barrels. Most of the materials can be purchased at
a hardware store and the cost of the system is about $250.
The system features vector control, zero leachate discharge to native soil,
aeration and moisture control of the compost and construction of durable,
non-corrosive materials. Although the system is designed for use in mild
climates, we've used it in places as diverse as Arizona and Oregon. The
reason for use in mild climates is that the composting chambers are
outdoors and sufficient warm weather is needed during the year for
proper composting to take place. An
approximate guide to appropriate climates for this system is USDA Plant Hardiness Zones
8 or higher. It the barrels were located in a garage or other
building protected from temperature extremes, it would probably work
fine in colder climates.
This system requires occasionally emptying buckets containing fecal
matter and is therefore not for the fecophobic. However, it is not the
smelly, objectionable process that one might imagine it to be. The
buckets contain mostly odorless cover material and the process requires
only about 15 minutes every 10 days or so.
I believe this system performs as well as any
certified composting toilet in terms of pathogen and nitrogen levels despite its simple
design. Unfortunately, it is doubtful, given the current regulatory
climate, that it could be permitted. Regulators are typically cautious
about what they will grant permits for and most feel that a toilet system
requiring manual emptying of buckets containing feces into a composting
chamber involves too much risk of contamination. Obviously, preventing
communicable disease should be taken seriously. On the other hand,
it's not nuclear waste that is being handled. Indeed, it is difficult
to see how the risk of contamination during routine maintenance of a
bucket toilet system differs significantly from cleaning oneself after
defecation. In either case a similar risk of contamination exists
requiring similar precautions (especially hand washing). I know of many
people (including a medical doctor) who have been using bucket toilet
systems for many years without problems. Hopefully, the perspectives of
regulators will change as bucket toilet users accrue more
evidence of the relative safety of such systems. It should be noted that
this particular design
could also be modified to function without the bucket aspect by fitting
a toilet seat and vent directly on top of the barrel composting chambers. With this modification a permit
might be granted for the system in some jurisdictions. For more
information on this, see our
Barrel Toilet webpage.
In the bucket version of the system, which is what we use, separate 5 gallon
buckets are used for defecation and urination. Buckets containing feces
and cover material are periodically emptied into composting chambers made from 55 gallon
plastic barrels. Urine, which is collected in a separate bucket, is diluted with water and emptied
daily into mulch
basins around trees and shrubs. The number of buckets and barrels used
is flexible and is based on the number of people using the system.
Composting toilets address only one aspect of the wastewater flow.
For a description of our current blackwater and graywater systems, see
Following is a description of the composting
components and processes:
We use three 5 gallon plastic buckets as toilet
Each bucket has a gasketed, leak-proof lid and is purchased from
hardware stores for about $6, including lid. The toilet buckets are used
primarily for defecation, although the system accommodates urination
that occurs during defecation. As the photos below show, the toilet buckets can be
located either outdoors in remote locations or indoors in urban
When a toilet bucket is about 2/3-3/4 full, a lid
is snapped on, the bucket is removed and a clean bucket with a few cups
of cover material in the bottom is put in its place. A bucket containing
cover material sits conveniently beside the toilet (more on this
below). Enough cover material is used to completely cover feces and
toilet paper after each use (typically 3 to 6 cups per use). We keep a 1 qt. plastic
bottle with squirt
cap next to the toilet for moistening toilet paper after use. This
reduces the volume of the toilet paper and allows the toilet paper to be
covered using less cover material.
With 2 adults using the system, it takes about 10
days to fill all 3 toilet buckets. The buckets are then emptied
into an outdoor composting chamber constructed from a 55 gallon barrel.
The compost in the barrel is manually aerated each time buckets are
A separate 5 gallon bucket with lid is used for
urination only. The urine bucket is emptied on a daily basis,
either full strength onto a compost pile to provide extra nitrogen, or
diluted with at least 8 parts water to 1 part urine and
emptied into mulch basins around shrubs or trees as described on our
Water Reuse page. The bucket is then rinsed
and returned to the bathroom area.
Outdoor toilet version: Our outdoor toilet
in Arizona is located behind a privacy screen of mesquite branches. The
toilet was constructed by cutting a 5 gallon bucket in half to
make a base and a top for the toilet bucket. The bottom 8 inches of the
cut bucket serves as a base to stabilize the toilet bucket while in use.
The base is buried in the ground about 6" deep. A
couple inches of sand are put into the bottom of the base to help
prevent the toilet bucket from becoming stuck in the base. A plastic
toilet seat/lid, available from camping supply stores for about $5, is
snapped onto the top portion of the cut bucket. This makes a seat
assembly which is inserted into the toilet bucket. The function of the seat assembly is to keep the
bottom of the toilet user several inches higher above the toilet bucket
contents, which allows the toilet bucket to be filled somewhat fuller
before it needs to be replaced.
This outdoor toilet has no roof. If it rains, we use an umbrella.
It's really quite pleasant.
Outdoor toilet in remote area (Arizona). From
left to right--gray bucket contains toilet paper. Toilet bucket with
snap on lid/seat. 1 qt. water bottles for moistening toilet paper.
Container of cover material. Two extra toilet buckets. (Urine bucket
Toilet bucket details. Seat assembly (being held above toilet
bucket) slides down into toilet bucket. Toilet bucket goes in base
(at left) and is ready for use. (see description above)
Indoor toilet version: Our indoor toilet in
Oregon consists of a 5 gallon bucket inside a wooden cabinet with hinged
lid. The cabinet is made from 3/4 inch plywood. The cabinet
has no bottom.
Indoor toilet. Bucket of cover
material containing wood shavings on right and urine bucket on left.
Toilet cabinet with lid up.
In Arizona, we use mesquite duff (dry and partially decomposed leaves)
which are raked up from under large mesquite trees. This is passed
through a 1/2 inch hardware cloth to separate out twigs and other
debris. We take care to rake up as little dirt as possible with the
duff. In Oregon, we have been using purchased wood planer shavings for cover
material (these contain no treated wood shavings). The wood shavings are
clean and pleasant to use, but take a long time to decompose, so we're
considering switching to
Mesquite duff (leaf) cover
material used in Arizona.
Wood shaving cover material
used in Oregon.
The composting chambers are constructed from
food grade, polyethylene barrels purchased in nearly new condition (used
one time only). They are
purchased from bakeries for about $15 apiece. The top of the barrel is
cut out about 1 inch in from the edge using a power sabre saw. The
barrel is then painted a dark color using oil based paint. This
protects the barrel from UV deterioration and helps with heat absorption
from sunlight. The barrels should be located outdoors and in a sunny
location. In windy locations, the barrels could be secured by driving
several 1/2 inch diameter by 4 foot long stakes made of rebar into the ground around each barrel.
There are no holes in the bottom of the barrel
since this is designed as a zero discharge system, meaning that all
liquid (leachate) remains in the barrel, where it eventually evaporates.
The leachate includes the small amount of urine excreted during
defecation as well as the small amount of water used in bucket cleaning.
For insect vector control, a 3 foot diameter piece
of fiberglass screen or insect netting is secured around barrel tops using a piece of 1/8 inch nylon cord
about 7 feet long and a spring. The cord is adjusted so that the spring
provides a light tension, yet allows the cord to be removed and replaced quickly and
easily. For animal vector control and to
prevent rainwater from entering, each barrel is covered with a lid of
galvanized corrugated roofing 26 inches square. The corrugations permit
airflow to the compost. The lids are secured with masonry blocks.
Barrels are filled to within about 6 inches of the
top. One barrel is filled at a time and a sufficient
number of barrels are used to allow feces to compost for a minimum of 1
year to help insure pathogen destruction. For example, in full time use, 2 people
will fill one 55 gallon chamber in about 2
months. So, if 2 people are using the system, 6 barrels are
1) Compost chambers made from
55 gallon polyethylene barrels.
2) Lid made from corrugated
metal roofing secured with masonry blocks.
3) Lid with blocks removed.
4) Insect screen with lid
removed. Note cord and spring for securing screen.
5) Detail of cord and spring
for securing screen. Spring is 5/16 inches in diameter by about 5
inches long. Cord is 1/8 inch nylon about 7 feet long. Cord is
knotted into ends of spring.
6) Top of chamber with screen
removed. Object in center is compost thermometer.
Emptying buckets: Toilet buckets are
emptied when all 3 buckets are full. 1 qt. plastic bottles with squirt
caps are filled with water and used to rinse buckets. One bottle is
used for cleaning each bucket although only half or less of each bottle
is used. To prevent contamination from spray, pressurized water from
hose or other source should not be used. Emptying and cleaning 3 buckets
takes about 15 minutes. Hand washing is the final and most important
step in the process.
1) Full buckets are carried to
compost barrels. Note stand with spray bottles and toilet brush at
2) Bucket is dumped into
barrel, then bucket side is slapped several times to dislodge any
3) After dumping, bucket is
rinsed with water.
4) Bucket is scrubbed with
toilet brush, then water is dumped into chamber.
5) Bucket is rinsed again and
rinse water is dumped into chamber. After all buckets are emptied
and cleaned, screen and lid are replaced on barrel.
6) Bucket is turned upside down
to drip, then a few cups of cover material is put into bottom of
bucket and bucket is returned to toilet area. Hand washing is
the final step in the process.
Aerating compost: Since
the composting barrels have no air vents or leachate
drain, thorough aeration, moisture control and mixing of the compost are
particularly important. In the process of experimenting with this
system, we tried a variety of manual compost aerators without success. Finally
we discovered the Compost Crank. This well designed tool is made of
stainless steel and works far better than any other aerator we've tried.
Although we don't have long experience with the Compost Crank, it is
already obvious to us that it is essential to the success of this system.
What the Compost Crank does is to pull wet material up
from the bottom of the composting chamber, effectively aerating the compost and
distributing moisture in the process. Temperature and visual
inspection of compost indicate good breakdown. The Compost Crank costs
about $35. (Note: We
have no financial connection with the manufacturer of this tool).
The tool is cranked into the compost until the
spiral end contacts the bottom of the barrel. Without further cranking,
the tool is then pulled straight up until the spiral end reaches the
surface of the compost. The process is then repeated in another part of
the compost until all compost is thoroughly mixed and aerated. The Crank
is stored in a length of 4" plastic pipe when not in use. The final and
most important part of the aeration process is
process is done each time buckets are emptied.
1) Compost Crank
2) To use, crank tool until
spiral end reaches bottom of barrel.
3) Without turning crank
further, firmly grab handle.
4) Slowly pull crank straight
up until spiral end of Compost Crank reaches surface of compost.
Repeat in another part of compost until all compost is mixed and
aerated. Replace screen and lid on barrel. Not shown is the final
step, which is hand washing.
A holder for compost crank made
from 4" ABS pipe about 2' long. Pipe is buried in the ground
Emptying compost chambers: After 4 months
of composting (since the last bucket was emptied into it) the contents
of a compost barrel are emptied into a wheelbarrow using a shovel. We
lay an old sheet down first and then place a screen of 1/2" hardware
cloth on top of the wheelbarrow. Any compost that will not pass
through the hardware cloth is dumped onto the sheet (typically, there
are a few gallons of material that don't pass through the screen).
When the barrel is nearly empty, it can be turned upside down to empty
the last bit of compost. The sheet is then gathered up and the
larger pieces of compost are dumped back into the barrel for another 4
months of composting. The barrel is then ready to be filled again
and the cycle is repeated.
The screened compost compost makes excellent mulch/fertilizer
around trees and shrubs. We also use it as the the growing medium in our
salad garden, but in that
application, we further age it for a minimum of a year before using.
Empting a compost barrel
Statistics: Here are some technical details
we've observed during the past 2 years:
-cover material use is 3 to 6 cups of cover
material per person per day (although this is more than necessary for
composting, we prefer to thoroughly cover all deposits)
-for 2 people in full time use, a 5 gallon bucket
will be filled to 2/3 to 3/4 full in about 3-4 days
-for 2 people in full time use, one 55 gallon
barrel will be filled in about two months
-for 2 people in full time use, about 1 to 1 1/2
gallons of urine per day will accumulate in the urine bucket
-as average ambient temperatures vary from 50 to
80 degrees F from winter to summer, temperatures at center of compost range from 60 to 110 degrees
We have been using this composting toilet method
on a full time basis for the past 3 years. It has met its design
goals of simplicity, low cost and ease of replication. We find the
system safe and easy to use and the temperature and visual appearance of
the compost indicate good decomposition.
We also recently added an insect trap to the
system after occasionally experiencing flies in the compost barrels.
Constructing and installing the insect trap is described in detail below. (More information on insect
traps can be seen on our other composting toilet pages.)
3-1/2" diameter hole carefully
cut in side of barrel (top of hole is about 2" below top of barrel)
Finished hole (1/2 round file
is used to smooth edge of hole)
Trap receptacle is made from 2 pieces of 3" ABS pipe coupling
and a 1-3/4" long piece of 3" ABS pipe
Cutting the 2 pieces of 3" ABS pipe
One piece of coupling is slipped
over the pipe and glued. The coupling/pipe assembly is then
inserted into hole in barrel and second piece of coupling is glued
to pipe on inside of barrel.
Coupling/pipe assembly installed in barrel.
Strap is bolted to barrel and will secure trap in barrel. Note adjustable buckle on
Trap components include canning
jar, top of 1/2 liter plastic drinking water bottle and canning ring.
Marking plastic bottle for cutting.
Cutting bottle with sharp knife.
Parts for trap ready to assemble. Top of
plastic bottle is inserted into mouth of jar and secured in jar with
Assembled trap. Note that top of plastic
bottle has been marked and cut cut at an angle. It is then
inserted into the canning jar so bottle mouth angles upward inside
jar. Insects are attracted upward toward light, so upward
angled bottle allows them to enter the jar more easily.
Finished trap installed in barrel.
Barrel composting chambers showing installed insect traps. At
right are the compost crank and screen for sifting finished compost.
Note stand for bottles and toilet brush used to clean buckets.
Trap will be most effective if it faces south, as more light will
enter it, attracting more insects.