The Arborloo (tree toilet) was researched by Peter Morgan and introduced in his book “Ecological Sanitation in Zimbabwe – A compilation of manuals and experiences (Volume 1. 1999).
It represents the simplest toilet system in which recycling of human excreta is possible. It consists of a small shallow pit toilet which is filled with a mix of soil, ash, leaves and excreta. Sometimes only ash or soil is added. These ingredients convert into a type of compost underground and out of sight.
The structure is simple and portable and mainly provides privacy. The additions of soil and ash also reduce odour and fly breeding.
In this model there is no handling of excreta. Once the shallow pit is nearly full the structure is moved to another site where another shallow pit has been dug. The original site is covered with a thick layer of soil and a seedling tree is planted in this soil. At first the roots of the young tree grow in the soil, whilst the combination of soil, excreta ash and leaves are converting beneath. Eventually the roots penetrate the organically rich layer below.
Whilst the young tree can be planted at any time, it is best planted at the onset of the rainy season, and is therefore assured of a more reliable supply of water.
The idea of planting trees on old used pits is not new. The Pilgrim Fathers are thought to have used the concept when they arrived in the New World, and sometimes trees can grow out of abandoned pits naturally.
The Arborloo concept has been used quite widely in countries like Malawi and Ethiopia, but has also been used elsewhere in Africa.