Summary

Since 2007, AIDG has done several public dry composting latrines in Cap Haitien, Haiti in partnership with the local NGO SOIL.

The latrines are equipped with two chambers where waste is converted into fertilizer. Only one chamber is used at a time while waste in the other dries and decomposes.  In addition, there are 2 toilet bowls (one for adults and a shorter one for children) that separates urine and feces, a urinal, and pipes that divert urine to a separate container.

Information on the basic design of urine-diverting toilets can be found in Hesperian Foundation’s Sanitation and Cleanliness for a Healthy Environment [available free as a pdf on their site, 52 pages]. The toilet seats for these installation where made using a fiberglass mold from Mexican NGO Centro de Innovacion en Tecnologia Alternativa A.C. (CITA)

The good:

Unlike a pit latrine, a properly maintained dry composting toilet is odorless. The special urine diverting toilet seat and urinal prevent excess liquid in the system, a key cause of bad sewage odors. The dry material (e.g. dirt, ash, grass, leaves, sawdust) added to the toilet after each use further absorbs excess moisture and aids in the composting process. Over a period of 6 months to a year, most pathogens and parasites, including roundworm eggs are killed in the dry conditions. Once fully composted, the treated human waste becomes a rich and safe organic fertilizer which can be used on both edible and non-edible plants. Urine collected in a separate container (e.g. plastic jug, etc.) can be mixed with water and also used as nitrogen rich fertilizer.

These above ground systems, which provide easy access for emptying, are a great solution in places where the groundwater level is high or there is risk of flooding. This latrine design has the capacity to serve 200-300 people.

The bad:

Proper use of a dry composting toilet requires training as these latrines work differently from pit latrines, overhang toilets, etc. Specifically, dry litter must be added after each use to prevent unpleasant odors and to accelerate decomposition.

Human waste, which its potential store of cysts, worms, harmful protozoa, etc. takes a year of composting before it is safe for use on crops. Testing to verify the safety of the final product should be performed before use on edible plants. While humanure is a great source of soil nutrients, many are not particularly keen on using it (or urine) as fertilizer. There are also cultural prejudices in handling latrine waste that must be dealt with.

AIDG is working with SOIL on setting up a municipal compost site. They have identified agro-businesses that are interested in the fertilizer if it proves to be without harmful pathogens after the year-long composting/decomposition period. Surveys of families with latrines have indicated that there is demand for an emptying service. One of the businesses that we intend to create will be involved in the emptying of wet latrines for biogas production and dry latrines for compost.

The bottom line:

Dry composting latrines are a safe and sanitary way to deal with fecal material in locations where municipal sewage services are absent. It is a particularly good option at sites where flooding occurs and/or where the water table is high. These latrines can be permanently sited as opposed to pit latrines and do not require water.

The community-scale public toilets installed by AIDG and SOIL are pay toilets (1-5 gourdes). The proceeds pay the wages of the toilet attendant who makes sure the units are stocked with toilet paper, kept clean, and properly used. An improperly maintained dry composting toilet is a smelly toilet. These monies however are not enough to cover humanure testing, distribution or disposal after the year long composting period. In cultures where individuals do not wish to use humanure and urine as fertilizer, alternative solutions for final disposal/use of waste must be sought. 

Note: An important problem in high traffic areas or areas where there are not other attractive toilet options is rapid filling of units. Partially composting waste may need to be moved to a different site where composting can be completed so that the latrines may stay open for use.

 Base Specs

Parts:

Capacity: 200-300 people

Cost: around $2500 for materials and labor

Pictorial How-to (Part 1)

What follows is a rudimentary step by step guide to the construction process. Photos are from the 2 builds.

The Foundation

Outlining the base of the toilet.

Prepping the site. The trench for the foundation is dug.

Foundation is built in a footing of poured concrete. Because Shada is prone to flooding and has a high water table, the foundation will ensure that feces will not leak into the groundwater.

The form is filled with a layer of sand, then gravel …

… then reinforced with wire mesh…

… after which a layer of concrete in poured, smoothed and allowed to cure.

The two chambers

Once the foundation has dried enough, the two chambers of the latrine can be built. Spaces between the two chambers are left for the vent pipe and pipes for urine diversion from the urinal and toilets.

Constructing the floor slab

Wood is used to construct the formwork that covers the chambers. Bamboo stalks are used to support the wood underneath.

Wire mesh and rebar are placed to reinforce the floor. Note spaces are left to accommodate where the toilet holes will be.

Building the stairs.

Molds for the toilet holes and pouring the concrete floor. Four plastic buckets are used to form the mold for where the toilet holes will be located for the 2 chambers. The concrete is poured and allowed to cure.

Lids for unused toilet holes.

Building the toilet house out of concrete block.

Finishing touches. The roof and door are added as well as a few accents. The chambers are sealed.

Urine Diverting Toilet and Urinal

Unfinished interior with urinal and 2 toilets (1 for adults, 1 for children). The simple urinal was constructed from cement with a wooden mold.

Urine collection drum and air vent. Hoses drain urine into the urine collection drum.

Pa jete fatra andedan twalet la!!! Don’t throw trash in the toilet. Latrine design allows for natural light and ventilation.

Toilet finished and painted is ready for use.