The Barrel Composting Toilet system utilizes 55-gallon high-density polyethylene barrels in a batch-type toilet system. A toilet seat and ventilation assembly is placed on top of an empty barrel. This barrel is known as the “active” barrel. When the active barrel is full, it becomes an “aging” barrel. At this time, the seat and ventilation assembly is moved to another empty barrel, which now becomes the active barrel.
The contents of the aging barrel will now compost for a minimum of 4 months with no additional material being added. The aging and active barrels are aerated once every two weeks using a Compost Crank. At the end of 4 months, the oldest aging barrel is emptied. The compost is deposited into mulch basins around shrubs, vines or trees or put into an outdoor composting bin for further composting.
Maintain an ample quantity of dry, fine, high-carbon cover material beside the toilet at all times. The following materials are recommended:
--Sawdust can be obtained from cabinet makers, lumber yards, etc. Avoid sawdust from cedar, redwood, treated wood or plywood.
--Wood planer shavings can be obtained from pet stores, feed stores, cabinet makers, etc. Avoid shavings from cedar, redwood, treated wood or plywood.
--Straw should be chopped so that all pieces are less than 3-4” long.
--Leaves can be used if they are dry and shredded. Gathering leaves in the fall and shredding them using a lawnmower with catchment bag works well. Leaves may harbor insect eggs which can hatch out inside the toilet. Also, leaves tend to create dense, heavy compost which is somewhat more difficult to aerate than lighter-weight materials.
--Shredded paper also works, but is not as absorbent as the above materials.
--Dry horse manure can be put through a chipper/shredder to pulverize it into a finely textured, absorbent cover material. If the horse manure is gathered from gravelly soil, screen all the manure through a 1/2 inch hardware cloth to remove any gravel that may be mixed with the manure.
--A paintbrush kept beside the toilet is handy for sweeping bits of cover material back into the toilet.
Note that cover materials differ in their ability to absorb liquid. If you are experiencing too much or too little moisture in your active barrel, you may want to change the cover material you use. For more on this, see our Cover Material web page
A 1 quart plastic bottle with squirt top works well to moisten used toilet paper, which facilitates composting of the toilet paper. The squirt bottle should be located beside the toilet. Maintain ample water in the squirt bottle at all times. All used toilet paper should be put into the toilet. Used toilet paper is then thoroughly moistened with water from the squirt bottle. Moisten only the toilet paper, not the surrounding compost.
other important use of the squirt bottle is for rinsing the urine diverter after each use. A squirt or two on the inside surface of the diverter, which in turn thoroughly rinses the inside of the urine hose, helps to prevent mineral scale buildup from the urine.
As feces and cover material begin to build up, forming a “peak” under the toilet seat, the peak will need to be “knocked” or flattened. Typically, this will need to be done 2-3 times per week. The Compost Crank should be used for this purpose.
Even better than flattening is to form a depression in the compost. This will help to minimize the amount of cover material needed to completely cover all feces and toilet paper. This is best done right after wetting down the toilet paper after defecation.
With the toilet lid and seat open, put the Compost Crank into the toilet with the spiral end resting on the surface of the compost, right beside the feces. Turn the Crank so the spiral end goes down into the compost about 1 foot. Now, slowly lift up on the Crank while moving the Crank toward the opposite side of the barrel. (Lifting up quickly on the Crank may fling compost onto the top of the toilet.) Repeat several times until a hollow area is formed below the toilet seat. Sprinkle a thin layer of cover material over the compost.
Some fecal matter may remain on the spiral and shaft of the Compost Crank. To help remove it from the spiral, turn the Crank into the compost about 1 foot deep, then slowly turn the Crank back out of the compost. Repeat if necessary. Crank can also be cleaned using toilet paper, or by wetting down the Crank with water from the squirt bottle, then using a toilet brush.
Store the Compost Crank in its receptacle after use.
A paintbrush is handy for sweeping bits of compost back into the toilet.
Urine management is important in all composting designs. In the Barrel Composting Toilet System, urine separation is an integral component. The recommended method is to install a urine diversion system on each barrel. For instructions, see Barrel Composting Toilet System: Urine Diversion System.
Alternately, one can urinate into a 5 gallon plastic bucket. A snap on toilet seat such as that manufactured under the name Luggable Loo makes seating more comfortable. These are available online and at camping supply stores. Alternately, a Gamma Seal lid can be used.
The urine bucket should be located beside the composting toilet and clearly marked. The urine bucket should be emptied daily. Dilute urine by adding 5 parts water to one part urine, then empty bucket into mulch basins around shrubs, vines and trees. Rinse bucket and return it to the toilet area.
Urine is an excellent source of nitrogen for plants, but is strong and can be overdone. A good guide for two people in full-time use is to maintain 7 mulch basins, each 3-6 feet in diameter. Designate one basin for each day of the week. Increase the number of basins depending on number of people using the toilet.
As noted above, cover materials differ in their ability to absorb liquid. If you are experiencing too much or too little moisture in your active barrel, you may want to change the cover material you use. For more on this, see our Cover Material web page
Aerating should be done at least once every two weeks. Aerating the active barrel may be done more frequently to help prevent odors. In hot weather, odor prevention may require aeration several times per week. The barrel containing the oldest material should be aerated first, then the next oldest and finally the active barrel. This insures that pathogenic material will not be transferred from fresher to older material.
To aerate, remove the rain cover and screen from the oldest aging barrel. Crank the Compost Crank down into the compost about 1 foot deep, then lift the Crank upwards. Do not crank as you pull it up. If this seems easy, crank deeper into the pile, repeating until the Crank contacts the bottom of the barrel. Repeat this process 10-12 times at various places in the compost, going all the way to the bottom of the barrel before moving to a new location in the compost. All parts of the compost should be thoroughly aerated when finished. Replace screen and rain cover, then repeat on next oldest barrel and finally on the active barrel.
As noted above, some fecal matter may remain on the spiral and shaft of the Compost Crank. To help remove it from the spiral, turn the Crank into the compost about 1 foot deep, then slowly turn the Crank back out of the compost. Repeat if necessary. Crank can also be cleaned using toilet paper, or by wetting down the Crank with water from the squirt bottle, then using a toilet brush.
Store the Compost Crank in its receptacle after use.
A paintbrush is handy for sweeping bits of compost back into the toilet.
To help prevent insects from entering barrel you've just aerated, the screen and rain cover should be replaced before beginning to aerate the next barrel.
Moving top assembly from one barrel to another:
When a barrel is full, the toilet top assembly must be moved to an empty barrel. To do this, remove the lower end of 4 springs that secure the top assembly to the anchor bolts on the side of the barrel. Lift top and place on empty barrel, taking care to guide the 4 locator bolts on the top assembly into the holes in the rim of the barrel. This is easier if the toilet seat and lid are open so the ends of the front two locator bolts can be seen.
After a minimum retention time of 4 months, the composted contents of a barrel are emptied. The recommended practice is to use an ordinary round bladed shovel to empty the contents into a wheelbarrow as described below.
Two common misconceptions about the system should be addressed here:
One is that emptying a barrel is an arduous and unpleasant task. It isn’t. After 4 months the barrel will only be about 2/3 full of relatively lightweight compost.
The other is that aging barrels will need to be moved for emptying. They do not. Aging barrels are heavy and should not be moved. The following procedure can be completed in less than 20 minutes.
Spread a tarp or large sheet at least 8 feet square on the ground beside the aging barrel to be emptied. Place a wheelbarrow on the tarp beside the barrel. Remove the rain cover and screen from the barrel. Dig the shovel into the compost and empty it into the wheelbarrow, repeat until the barrel is empty or nearly so. It’s fine to leave some compost in the bottom of the barrel.
Gather up the tarp and deposit any spilled compost into the wheelbarrow.
Spread the compost in mulch basins around shrubs, vines or trees or deposit it into an outdoor composting bin for further composting.
Transfer the toilet seat assembly to the top of the now empty barrel, which now becomes the active barrel. That’s it, you’re done.
If you want especially fine compost, place a 2 foot by 4 foot screen of ½” hardware cloth on top of the wheelbarrow and sift each shovel full of compost though it. Pieces of compost too large to go through screen should be dumped onto the tarp. When finished, gather up the tarp and deposit the larger pieces back into the barrel.
This results in a fine, aesthetically beautiful compost.
Tips and Troubleshooting:
If odor problems arise it indicates that one or more of the four essential elements of composting is out of balance. Typically, the carbon/nitrogen ratio is out of balance, the compost is too wet and it isn’t getting enough air. All of these can be remedied by adding dry, high-carbon cover material and then thoroughly aerating the compost. As mentioned above, odor prevention in hot weather may require aeration several times per week.
Pay attention to the compost as you aerate. If it appears moister than a wrung-out sponge, check the urine drain hose to make sure it's secured in the bottom of the urine diversion funnel. Then add more absorbent carbonaceous material and aerate again. (See our Cover Material page for more information on the absorbency of cover materials.) Very wet compost may require the addition of large amounts of absorbent, carbonaceous material, in some cases 10-15 gallons or more. After adding absorbent carbonaceous material and aerating, odors should be eliminated almost immediately.
Normally, insects and other arthropods will be excluded from the compost by the insect screen over all vents and the weather stripping around the toilet seat on the active barrel and by the insect screen on top of the aging barrels.
Occasionally however, insects may enter a barrel and can hatch out in large numbers. This occasionally occurs in all composting toilets. The fly trap can help to control this in the active barrel. If you notice insects in the barrels, first check that the weather stripping around the toilet seat is entirely intact, with no gaps. Even a small gap can allow insects to enter.
Some of the more common arthropods include:
--Soldier flies. These harmless wasp-like insects in the fly family are black and about ¾” long.
--Fungus gnats. Also harmless, they are small, flying insects about 1/8” or less in length. The smallest gnats can pass through the standard insect screen used on the vents of the active barrel and on the tops of the aging barrels. A screen with a much finer mesh, known as 'no-see-um netting', will help prevent gnat entry and can be used in place of regular insect screen. It will restrict air movement somewhat more than standard screen, so more frequent aerating may be required. For no-see-um netting suppliers, check fabric stores, camping supply stores, military surplus stores or online.
--Mites. These are tiny, wingless arthropods, usually less than 1/16” in size.
--House flies. These are potential disease vectors because they are attracted to both human feces and human food, so can spread disease from one to the other.
following methods are recommended to prevent insects from entering toilet and to eliminate them if they do.
Condensation in active barrel:
Condensation may occur on the underside of the toilet lid and seat if the toilet is in an outdoor location and nighttime temperatures are cool. To help prevent this, either use an insect plate as described above or put a piece of plastic sheet about 16" square over the toilet seat hole, then close the toilet seat and lid on top of it to hold it in place. Plastic sheet can be cut from a garbage bag, plastic tarp, etc. Also, plastic sign material such as that available from a hardware store for "For Sale" type signs works well. This type of material should not be over 1/16" thick or it may damage the weather stripping on the toilet seat. For that reason, don't use the thicker, corrugated plastic sign material.
Large holes in screen on top of aging barrels:
These can be caused by mice. If tools, etc. are leaned against the side of a barrel, mice can use them as a ladder to gain access to the top of the barrel. Tools, plants, etc., should not be allowed to contact the sides of barrels.
Stopped up urine diverter hose:
in repeated contact with hard surfaces tends to form mineral scale. This is unsightly when it occurs on the inside surfaces of the urine diverter. When it occurs on the inside surface of the urine diverter hose, it may eventually lead to clogging of the hose. Preventing this buildup is simple. As noted above, after each use of the urine diverter, it should be rinsed with water from the squirt bottle. A squirt or two into the diverter rinses it and also thoroughly rinses the inside of the hose, helping to insure that the diverter hose will not become clogged up over time.
If for any reason the urine hose does become clogged, the easiest way to clear it is to use a micro-plumbing snake. Make one by getting a used Shimano-type bicycle derailleur cable, available free at any bicycle shop. At one end of the cable is a barrel-shaped end that looks like the one in the first photo below. Using a file, gently and carefully round off the edges of the barrel-shaped end.
The snake can then be pushed, barrel-end first, down the urine drain hose until it comes out inside the underground bucket leaching chamber. As it does so, it will push the blockage into the leaching chamber.
Note: It's important to round off both edges of the barrel-shaped end, as shown in the second photo below. Rounding off the front edge allows the cable to pass through the drain hose easily. Rounding off the back edge keeps the cable from becoming hooked on the end of the hose inside the leaching chamber.
Shimano-type derailleur cable end
Derailleur cable end after rounding edges with file