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In short
Set in Kiberia, one of the many suburbs of Nairobi, Kenya, bio-latrines are set to replace standard latrines that show poor maintenance and bad sanitation. Each unit generate gas that could then be used for domestic cooking or converted into electricity.
How the system works
Bio-latrine plansThe bio-latrine consists of three principal components. It is made of a conventional pit latrine, the bio-digester and the expansion chambers.
The pit latrine is dry with ventilation pipes to remove odors and trap flies. It differs from a standard pit latrine in that the bio-latrine unit is shallow and feeds directly into the bio-digester.
The bio-digester is a large underground dome, which during normal use is filled to about half its height with the combined urine and fecal sludge. The bacteria in the sludge break down the pathogens in an airless process, producing the methane-based gas.
The gas collects in the space above the sludge and is led out through a plug, which seals the top of the dome. Methane is the principal gas produced by the latrine. The gas exits the digester through a plug inserted into its neck and is then piped through underground pipes directly to the appliances in homes or institutions.
Bio-latrine benefits
A bio-latrine in construction"The bio-latrine uses the technology of anaerobic or airless digestion to transform human waste into fertilizer and gas suitable for uses like cooking, heating and lighting," said Malcolm Ormiston, a Nairobi-based engineer and owner of Globology Limited.
The community is able to properly dispose human waste and at the same time reduce pollution and environmental degradation. The bio-latrine uses standard biogas-system designs commonly found in Asian countries such as China, India and Vietnam. But the marked difference between biogas digester and bio-latrines is that latrines use human waste instead of animal waste.
The toilet facility and digester are constructed using conventional building materials and require little maintenance. The systems are scalable and can thus cater for various sizes of populations, ranging from small settlements to large institutions.
The output gas is in the production of electricity from generators built by converted or purpose built internal combustion engines. Electricity generation is practical from large-scale biogas/latrine systems and calls for greater financial investment and effective management.