RESPECTFUL WATER CONSERVATION THROUGH

COMPOSTING TOILET AND LATRINE TECHNOLOGY

By Steven G. Herbert

            If a collapse of the infrastructure were to suddenly occur, perhaps the first effect felt of loosing the grid would be leaving Americans unable to flush their toilets. But considering an alternative to the flush toilet and centralized sewage treatment centers is not just a good idea to make us less vulnerable to infrastructure collapse. It is also an environmental advantage with respect to water conservation, at the same time that it affords the element of water its due respect. Offered here is an outline and a guideline to the decisions one must make in selecting or designing a dry toilet, more commonly known as a composting toilet or latrine system.

First system built in the US based on the Herbert design            Per capita consumption of water in the US is three times that of the average European and fifteen times that of the typical person residing in a developing country. By some estimates, of all the potable water that comes into the average American household, fully a third gets flushed down the toilet. With worldwide average consumption rates rising twice as fast as population, and population projected to double in forty years, its plain to see that soon flushing will be a luxury we can no longer afford. Water is essential to life, but with this gift comes the responsibility to promote sustainable use of this precious resource.

            Only a fraction of one percent of the earth’s total water supply is available for use, and these reserves are already strained. Surface supplies are shrinking while water tables lower. Groundwater is being withdrawn faster than it can be replenished. Such unsustainable water use can also have political repercussions as well as environmental. Eighty nations now have serious water problems which will become severe within twenty years. Twenty two countries depend upon other nations for a majority of their water. One hundred and twenty river systems in the world flow through two or more countries. The Niger, for example, flows through ten. Some say the next major war could be fought over water, not oil. We have already in some places seen the price of water rise higher than oil.

            Beyond the obvious necessity for responsible use of a precious commodity, is needed a new attitude of respect for a truly miraculous and sacred substance. Several attributes about water make life on earth possible. It is the only substance, for example, which becomes less dense upon freezing. Also it is the only material that passes through the three stages of gas, liquid and solid within the temperature range that living organisms can tolerate. But it is perhaps its electrical and energetic properties that make it most mysterious. As such, it is a powerful solvent, which is important to biological processes. Beyond this it is a carrier of life force within the body. Water has a memory, which is the principle upon which homeopathy works. By this quality water can become blessed and act as a powerful healing force. What are we doing to water by disrespectfully depositing our waste in it?

            Supplies may be increased by dowsing for live water, rainwater harvesting or desalinization, but we can show our respect most by conserving it in the first place. Agricultural practices may loose up to half its irrigation water in the process of distribution to evaporation and runoff. More efficient methods such as drip irrigation can make a big difference. Industry can potentially save a lot through water reuse. Within the home, more efficient washers, dishwashers and low-flush toilets can reduce significantly. The practice of “cascading”, or reusing dishpan or shower warm-up water in the toilet bowl or on outside plants can save more. But the biggest savings can be realized by eliminating flushing altogether.

The first Herbert systems were built in Africa below ground and with stoop plates. On left, the intitial prototype was built in Lambaye, Senegal. At right, one of five systems built in the Bambaye area of Senegal in a Peace Corps-funded project.

            Once committed to the idea of a dry or composting toilet, the first decision to be made is whether to purchase a pre-manufactured unit or have one custom built into the home. There are many brands to choose from; Clivus Multrum, Phoenix, CTS, Envirolet, Sun Mar, Nature-Loo, Rota-Loo, VERA, or Biolet, etc. Typically, these can be purchased either directly from the manufacturer or from a local dealer (see Resources at end of article). Prices range widely depending on the type of system purchased.

            Whether one chooses to purchase a pre-manufactured unit or contract one to be site built, the next decision is whether to have a self-contained unit or one which is centralized or remote. The former is easily portable such as one might have in a camp or hunting lodge, where there is no basement and use is seasonal or sporadic. A centralized system features a permanently mounted stool with the composting unit remotely placed in the basement or floor below.

            Self-contained units come with a variety of features, needing only to be hooked up to a venting system. Some designs may be fully adequate for year-round continual use. They may be single or multi-chambered, require electricity for heating and aeration or be totally non-electric. Models are available which dehydrate or incinerate the contents, but these are not truly composting. One may also opt for a home-made unit such as a sawdust toilet built of plywood and using an ordinary five-gallon plastic bucket (see Joseph Jenkins’ Humanure Handbook, pages 179 to 188). Starting with a little sawdust in the bottom of a bucket placed under the toilet seat, a scoop of rotted sawdust cover material is deposited after every use. When full the contents are transported to a composting area.

            The third design decision is whether your composting toilet will have a single vault or multiple chambers. Among pre-manufactured self-contained systems, if the unit is to be used continuously, especially by a family, then a multi-chambered model is pretty much a necessity. The centralized Clivis Multrum system by contrast, features a large continuous-use single vault. In this design, fresh material is deposited on top, and finished compost is removed from the bottom of an inclined chamber. The Phoenix system features a vertical chamber, and the manufacturer claims its design more efficiently prevents contamination of lower layers with fresh deposits. Most pre-manufactured remote systems, however, are only offered in a single vault option. This is why a custom-built, double-vault alternate-use or multiple-chamber rotating-use system has an added advantage.

            All the composting latrines I designed and built in Africa and Latin America are double-vault, fixed-batch systems. The larger-sized vault, made out of rammed-earth, ferro-cement or brick, had one cubic meter and a half capacity, enough for a large extended family or small school. A smaller version for an average-sized family featured a one cubic meter vault. In either, a stool or stoop plate was mounted over each vault. It might take as much as a year to fill up one, at which time the use is switched to the second, leaving the contents of the first to “cure” undisturbed. By the time the second vault is filled at the end of the following year, the first is ready to be dug out and reused. I was in Africa long enough to see the finished product from my original prototype. It looked like dark and rich chocolate cake.

Photo at left shows the first Herbert system built in Latin America, in Siguatepeque, Honduras. Seen a right, is the concrete urine-diverting seat with pail of dry flush material beside.

            There are alternatives, however, to dual vaults built permanently side by side. Another variation is a composting unit with multiple chambers which can rotate each time one is filled. Also, a single stationary unit may be designed to accept removable bins. In any case, the composting unit must be designed to manage, whether passively or actively, several key factors. These are: oxygen levels, temperature, moisture, Carbon to Nitrogen levels, and of course, pathogen levels. If all is operating ideally, the contents should be fully composted with all pathogens destroyed by the end of six weeks. Therefore, when calculating the capacity of each vault, to be safe, one should figure the time to fill it as a minimum of twice this, or three months.

On left, a scale model composting latrine with top removed shows the double-vault design. The photo at right shows a side view exposing the sloped concrete floor.

            Certain factors should be considered when making these calculations. Will the use be seasonal or year-round? Will it be mainly day-use only or continuous (day use tends to accumulate a much higher percentage of urine by comparison)? Here are the relevant statistics you will need. One person produces 40.6 fluid oz.s (1.2 liters) of urine per day. The same person also produces 20.3 fluid oz.s (.61 liters) per day of feces. Over a full year, that amounts to 155.8 gallons of urine and 57.9 gallons of feces, or a total of 1,300 lbs. of excrement. In terms of volume, that represents 20.8 cubic feet (.6 m3) of urine and 7.7 cubic feet (.2 m3) of feces per average person per year. Keep in mind that the volume of the contents will constantly decrease during the composting process. In fact, the volume will decrease to as much as ten to thirty percent of its original volume by the end of the incubation period.

            In the tropical climates of Africa and Central America, all the units I built were designed to operate passively, requiring minimal management. In temperate climates, the design may need to be more of an active one. This means a small electric fan installed in the vent pipe is needed to increase the efficiency of aeration, and an artificial heat source built in to keep the contents above “biological zero” (42 degrees F) and speed composting. For every ten degrees C rise in temperature, the composting rate doubles. This is known as “the Q10 temperature coefficient”. Different microorganisms operate at different temperatures. From 42 to 67 degrees F, actinomycetes and fungi dominate in psychrophilic or mouldering processing. At 68 to 112 degrees F, mesophilic bacteria operate under most typical conditions. Ranging 113 to 160 degrees F, thermophilic bacteria take precedence.

            The reason for aerating is partly to evaporate liquids, but most importantly to encourage aerobic decomposition. It is the anaerobic bacteria which are mainly the pathogenic and odor-causing microorganisms. Beneficial aerobic bacteria thrive in the higher oxygen and temperature levels which destroy the anaerobic organisms. If a composting unit is operating efficiently and is well ventilated, there should be no noticeable odor detectable from above. The amount of electricity required to operate the fan and heat source is not great, and may well be powered by a solar panel.

            Your next major design decision is whether to separate out urine or not. There are several advantages to separation. One is that it reduces moisture levels in the composter contents, hopefully to the ideal consistency of a well wrung out sponge. Second is that prevents the ratio of Nitrogen to Carbon from becoming too high. This is another cause of odors. Third is that it may virtually eliminate the amount of effluent you need to deal with (usually collected in a basal pan), otherwise by means of an evaporator. Urine separated out may be directed to an outside charcoal or limestone-filled soak-pit (as in the case of my latrines). It may also be directed to the conventional septic system, an evaporator, added to the greywater, or stored in a tank. The tank may be emptied periodically by a collection service, or used on trees, flowers or other non-food plants. Human urine is relatively sterile and actually has more nutrients than the feces, but it also has a high salt content. Urine-separating seats may be purchased to mount on your custom-made bench, or the entire bowl can be ordered if preferred. When seated, the urine is directed forward to be captured and drained separately. Women will find it more difficult to master but eventually do become accustomed to it. For men, it is advised to install a separate waterless urinal to supplement the composting toilet.

Various versions of urine-diverting toilet seats. At left, a seat of concrete, and center of plastic. On the right is a urine-diverting stoop plate.

            When beginning to use your new composting toilet for the first time, it is recommended that you cover the bottom of the composting vault with a few inches of good compost or rich soil. This adds the beneficial organisms that “inoculate” the system. It also provides a medium for liquids to soak into. After each use, it is also a good idea to get into the habit of using a “dry flush” material. The best recipe is one part compost or good soil to one part a dry carbon material such as straw, wood shavings, or bean chaff, etc. Sometimes a small portion of ashes can be added. The carbon material, especially wood shavings, act as a “bulking agent”, and helps prevent compaction of the contents and thus encourages aeration. Aeration may be further encouraged by interior mixers, grates, air channels, etc. However, these tend to be in the way when removing contents and present a maintenance nightmare if they need repair. Usually their liabilities outweigh benefits. Just remember, “one scoop per poop”, to cover fresh deposits and this will probably aerate adequately.

            In a centralized or remote system, the toilet seat or bowl needs to be mounted directly over the composting chamber with an average ten inch diameter drop pipe installed vertically for a straight shot. For any supplemental bathrooms in the house, one might consider a micro-flush toilet which would allow the plumbing to take a more circuitous route to the common composting chamber. It is advised that you construct the inside of your composting chamber with a slightly sloped floor so that the minimal leachate produced may drain forward to a collection device. Radiant heat may be designed into this floor. Otherwise, a submersible aquarium heater, a light bulb in a fire-proof box, or waste heat from a dryer duct may warm the contents. Build the unit a foot or so off the floor in case of flooding, and naturally, install an access port for removing contents and another for inspection or raking/turning contents.

Pictured from left to right are various systems built in Latin America based on Steve Herbert's design, the first two in Honduras, the third in El Salvador and the fourth in Ecuador.

            The laws in most states are still not very sympathetic towards this technology. Yet I feel it is the wave, even the necessity of the future. In most cases you will be required to have a conventional, or at least a reduced septic tank and leachfield, to handle greywater and for resale purposes. If you are fortunate, this technology may enable you to avoid building an expensive mound system. In any case, if you can get it approved by an engineer or site tech, your state or municipality may approve it also.

            There are many advantages that a single home composting toilet and accompanying greywater recycling system has over a conventional septic tank with accompanying leachfield or centralized sewerage treatment plant. The septic tank is a very inefficient composter which is dominated by anaerobic organisms. It acts mainly as a settler, and the effluent that reaches the leach-field is still laden with pathogenic organisms and toxic household chemicals. The risk to groundwater supply is obvious. The massive infrastructure required to centrally treat sewage uses high amounts of energy, large quantities of more chemicals, and a sizable chunk of your tax dollars. The result is a sludge, or euphemistically “bio-solid”, that must be land-filled as waste, incinerated to create pollution, or land-applied at considerable risk. Doesn’t it make more sense to process “waste” at its source, and create a valuable product we can give back to the earth?

For a school in Kenya, Steve designed a system with three pairs of composting chambers in one buliding, with a roof large enough to capture rainwater for handwashing. Left photo shows the entrance and in right photo is seen the removal ports.

            In conclusion, adopting composting toilet technology makes sense and has many advantages. Besides making us less vulnerable to infrastructure collapse by decentralizing, composting toilets are a significant means of water conservation. By their use, we show due respect to the miraculous and sacred substance which water is. Whether one adopts a pre-manufactured unit or custom designs a site-built model, there are several features which must be considered to decide which best suits your particular circumstances. If choosing a custom-built system, what is recommended here is a centralized or remote, double-vault fixed-batch or multiple-chamber rotating batch, urine-separating system. The elements of a composting toilet must be designed to, whether passively or actively, manage oxygen levels, temperature, moisture, C to N ratios, and pathogen levels. Such a system has many advantages environmentally and fiscally over centralized sewerage treatment facilities, and even over individual conventional septic tank and leach-field systems. Laws at present do not generally recognize this, but the trend will be toward more favorability as water conservation becomes an even more pressing need.

REFERENCES

Baumgartner, Rhetta Jacobson   Water: The Stuff of Life. American Dowser 32(2):9-11

Jenkins, Joseph C.   The Humanure Handbook. 1999 Grove City, PA: Jenkins Publishing

Montaigue, Fen   Water Pressure. National Geographic September 2002 202(3):2-33

Simon, Paul   Tapped Out: The Coming World Crisis in Water and What We Can Do About It. 1998 US: Welcome Rain Publishers

Steinfeld, Carol and David Del Porto   The Composting Toilet System Book: A Practical Guide to Choosing, Planning and Maintaining Composting Toile Systems, An Alternative to Sewer and Septic Systems. 1990

Utne Reader   The drying game. Der Spiegal May 25, 1992 in UR May/June 1993

Van der Ryn, Sim   The Toilet Papers 1978 Santa Barbara: Capra Press

RESOURCES

Ecovita (dealer of Separett and accessories), P.O. Box 1330, Concord, MA 01742-1330

(978) 318 7033   info@ecovita.net   www.ecovita,net

Biolet, 53671 Lafayette Township Rd 508, Fresno, OH 43824   1-800-524-6538   info@biolet.com   www.biolet.com

Clivus Multrum, Inc., 15 Union St., Lawrence, MA 01840   (978) 727-5591   1-800-425-4887   forinfo@clivusmultrum.com   www.clivusmultrum.com

Clivus New England, Inc., P.O. Box 127, N. Andover, MA 01845 (978) 794-9400   123CNE@clivusne.com   www.clivisne.com

“CTS” Toilet Composting Toilet Systems, P.O. Box 1928, Newport, WA 99156-1928

(509) 447-3708   (888) 786-4538   cts@povn.com   www.comtoilet.com

Envirolet Composting Toilet, Sancor Industries Ltd., 140-30 Milner Ave, Scarborough, Ontario M1S 3R3   Canada   (416) 299-4818   1-800-387-5126   info@environlet.com   wwwenvirolet.com

“Phoenix” Composting Toilet, Advanced Composting Systems, 195 Meadows Road, Whitefish, MT 59937   (406) 862-3854   phoenix@compostingtoilet.com   www.compostingtoilet.com   dealer: Ben Goldberg, P.O. Box 550, Leeds, MA 01053   (413) 586-3699   (413) 237-7060 (cell)   plunkatune@mindspring.com

Sun-Mar Corporation, 600 Main St., Tonawanda, NY 14150   1-888-341-0782

5035 N. Service Road, C-9, Burlington, Ontario L7L 5V2   Canada

compost@sun-mar.com   www.sun-mar.com   free catalog 1-800-461-2461

Eco-Tech, 50 Beharrel St., Concord, MA 01742   (978) 369-3951   ecotech@ecological-engineering.com   www.ecological-engineering.com/ecotech.html