Exhibition: Cities | October 5, 2011 by

In the slums and informal settlements of Nairobi, there is only one latrine for every 150 people. As a result, many resort to “flying toilets” or use open spaces after dark, which is a security risk for women and girls. Most latrine blocks are inaccessible to children, the elderly, and physically challenged. Waste overflow pollutes nearby streams, leading to diseases such as diarrhea, typhoid, and tuberculosis. Water costs four to five times higher at kiosks inside the slum so that many residents cannot afford to meet their daily needs, while dilapidated pipes leak and expose water to contamination.

Kenya-based Umande Trust worked with residents and artisans in the slums of Nairobi and Kisumu to plan, design, cost, procure, and construct the BioCentres. Built from conventional, locally available technology and materials and unskilled labor, the multi-story BioCentres convert human waste in situ without requiring infrastructure. The bio-latrine uses anaerobic, or airless, digestion, in which bacteria transforms human waste into fertilizer and methane-based gas for cooking and heating water, reducing carbon emissions. A shallow pit latrine feeds into a domed underground bio-digester and expansion chambers, which need little maintenance since there are no moving parts. Generated bio-gas and liquid fertilizer can be sold for income. BioCentres provide toilets free to children, washrooms and showers at a minimal fee, kiosks selling affordable clean water on the ground floor, and community and livelihood spaces on upper floors.

Designers: Michael Francis, Josiah Omotto, Peter Murigi, and Malcolm Ormiston, Umande Trust. Collaborators: Halcrow Foundation UK, Athi Water Services Board, Oxfam, Goal Ireland, UN-Habitat. Kibera, Korogocho, Mukuru, and Mathare informal settlements, Nairobi; Manyatta, Obunga, and Nyalenda informal settlements, Kisumu, Kenya, 2006–present. Bricks, sand, cement, ballast, reinforcement bars, timber, roofing materials


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