An Arborloo is an ecological sanitation toilet in which trees are planted on top of the full pit while the superstructure, ring beam and slab are moved from pit to pit in a continuous cycle.
The Arborloo is a shallow pit on which a tree can be planted after it is full, while the toilet superstructure, ring beam and slab are moved to a new pit in a continuous cycle (usually moved once every 6 to 12 months). The pit should be about 1 to 1.5 m deep and should not be lined as it would prevent the tree or plant from growing properly.
The tree or plant should not be directly planted in the raw excreta. It should be planted in the soil on top of the pit, allowing its roots to penetrate the pit contents as it grows.
Arborloo designs will vary between communities but the ecological sanitation principle remains the same. It can be applied in rural, peri-urban, and denser areas if space is available.
Implemented by various organisations including Catholic Relief Services in East Africa, Water, Agroforestry, Nutrition and Development Foundation (WAND) in the Philippines
Goal 6: Clean water and sanitation
Individuals and communities which have no access to improved latrines, do not use organic fertiliser or have the capacity to buy them.
The Arborloo is constructed in a series of stages involving a concrete slab, ring beam to protect the pit, and superstructure.
The superstructure is most often made from local materials and will vary between the location and level of investment the household is willing to make for the superstructure (e.g. woven reeds, sticks, bricks, cement). The household generally provides the labor to dig the shallow pit and build the Arborloo, which approximately takes 2-5 hours.
After the Arborloo is constructed, a layer of leaves, ash, or soil is placed in the pit prior to its use by the household. Once the pit is approximately two-thirds full, the pit is backfilled with a thick layer of soil and a tree is planted on the nutrient-rich pit.
The household digs another Arborloo pit once the first one is filled, and the concrete slab and superstructure are moved to the new pit. The superstructure, ring beam and slab are moved from pit to pit in a continuous cycle.
Open-source designs are available from several sources, including Sustainable Sanitation and Water Management Toolbox and Stockholm Environment Institute EcoSanRes Programme.
The Arborloo is an open-source design. It is commonly built by the end-users with local construction support where available.
Type of toilet
Method of evacuation
How the fecal sludge is stored
The holding volume of the containment
Time until emptying is estimated to be needed
The Arborloo design is comprised of three main parts:
- Concrete slab: The slab is made with an aperture for the squat (pedestal hole). This is typically cast offsite prior to transporting to the pit location.
- Ring beam: The ring beam is cast in-situ at the pit location. It is designed to protect the shallow pit and lift the concrete slab off the ground surface. Its approximate dimensions is a 1 m internal diameter and 1.3 m outer diameter. Once the ring beam is cured, a hole of 1-1.5 m depth is dug. Alternatively, steel barrels are sometimes used instead of a ring beam to support the pit from collapsing.
- Superstructure: This structure is built around the slab using local materials. It is designed to provide privacy to the occupant. It is also designed to be portable as the Arborloo will need to be transported to a new pit once the existing pit is two thirds full.
Schematic of Arborloo concept and stages of life
Local technicians and NGOs who are experienced in ecological sanitation in the respective country.
Replacements and repairs are carried out by the end-users with local construction support where available.
6-12 months prior to planting and cycling Arborloo to a new pit.
Specified performance targets generally referred to for the Arborloo are summarised below:
- Simple technique for all users
- Low cost
- Low risk of pathogen transmission
- Encourage income generation (tree planting and fruit production)
The Arborloo is mainly assessed for its applicability in rural environments in the context of promoting sanitation noting its varied designs as an open-source solution. This assessment has been undertaken by various organisations through field trials and case studies. Common conclusions include its recommendation as a preferred solution in rural environments because of its low costs, ease of construction and quick return on investments.
Assessments of this sanitation solution type have been carried out by a number of researchers and organisations including the International Water and Sanitation Centre.
Covering the pit and planting a tree reduces risk of infection due to reduced human contact with faeces contained below a layer of leaves and topsoil for separation. Users do not come into contact with faecal material reducing risk of pathogen transmission.
Complementary technical systems include roofing structure to protect end-user from weather, vent pipe with fitted fly screen and pedestal for end-user comfort. Soil and ash should also be readily available to be dispatched into the pit after each use to reduce fly and odour nuisance.
Dionna, F,. et al., 2015, Adoption and sustained use of the Arborloo in rural Ethiopia: a cross-sectional study. Journal of Water, Sanitation and Hygiene for Development, Vol 5., Issue 3, pp. 412–425
Shewa, W., Geleta, B., 2010, Arborloo for household sanitation, Arba Minch, Ethiopia. Case study of sustainable sanitation projects
Morabito, P., 2014, Plastic Arborloo Bases for Haiti. Multidisciplinary Senior Design Conference.
Simpson-Hebert, M., 2007, Low-cost Arborloo offers Ethiopians health and agriculture benefits. Waterlines, Vol. 26, no. 2, pp. 12-14.
The Arborloo has been primarily evaluated on terms of cost, constructability and quick return on investments in various contexts. Additionally, the solution type is also examined on why and how these factors are associated with adoption and sustained usage.
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