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A treebog is a type of low-tech compost toilet. It consists of a raised platform above a compost pile surrounded by densely planted willow trees or other nutrient-hungry vegetation. It can be considered an example of permaculture design, as it functions as a system for converting urine and feces to biomass, without the need to handle excreta.
The treebog is a simple method of composting wastes. Abrahams claims that from 1995-2011, around 1500 treebogs may have been built in Britain. They have been on sites ranging from fruit farms, pick-your-own enterprises, campsites, an angling lake, festival sites, remote/low impact dwellings, holiday cottages, allotments, and church yards where there is no mains water supply.
In 2011, Abrahams claimed that the treebog had attracted the attention of NGOs and aid workers who hope to develop its potential for shanty towns or refugee camps - anywhere that water is scarce and the population pressure on resources is high.
A treebog is simply a controlled compost heap whose function has been enhanced by use of moisture or nutrient-hungry trees. They use no water, purify waste as they create a biomass resource, and also contain the organic waste material, thus preventing the spread of disease.
The main requirement is that the planted species should be nutrient-hungry. It is a bonus if they can be harvested or coppiced for productive uses, e.g. willow cultivars. Apart from willow coppice, soft fruit such as black currants and sweet-smelling herbs such as mint will thrive around a treebog. If left unmanaged, a treebog will soon be surrounded by weed species such as nettles, but a little management and conscious planting can create a fertile and productive bog garden.
Both the solids and liquids are deposited within the treebog base, where the solids compost and the liquids soak through the soil. The associated dense root zone enables the nitrogen to be rapidly absorbed and metabolized by the mycorhyzal species. The feces are contained within the treebog base, which is well ventilated to allow aerobic decomposition to occur, the mineralized material feeding the trees around it.
A seating platform/cubicle is mounted at least one meter high. The area beneath the seating platform is enclosed by a double-layer of chicken wire; this acts as an effective child-proof barrier and allows air to circulate through the compost heap.This allows for optimum plant growing conditions.
Sawdust, straw, woodchip, ash or other high-carbon matter is used to balance the high-nitrogen content of the urine. One design used Effective Micro-organism bran, which helped keep the treebog virtually odour free.
The space between the wire is stuffed with straw, which acts as a wick to help sop up excess urine, preventing the likelihood of odour problems due to incomplete biological absorption of the nitrogen from the urine. The straw-filled wire also enables the pile to be well-aerated whilst acting as a visual screen for the first year’s use.
The structure is surrounded by two closely planted rows of osier or biomass willow cuttings; this living wall of willow can then be woven into a hurdle-like structure and its annual growth can be harvested.
- "The Making of a Biologic Treebog". LivingWoods Magazine: 10–13. January–February 2011.
- Tim Green (18 May 2011). "A Loo with a View - Build your own Treebog". Permaculture Magazine. Retrieved 23 February 2012.
- "Woodland Toilets or Tree Bogs". WoodlandsTV. 15 May 2009. Retrieved 23 February 2012.