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To many people, the term ‘flying toilets’ might sound like a new and sophisticated sanitation facility. Yet to the residents of Kibera, a slum in Nairobi, Kenya, it is a means used for sheer survival. Lest you are fooled, flying toilets are plastic bags carrying human waste that are thrown into the streets, alleys and ditches, on rooftops and anywhere else they might land. This method of human waste disposal contributes to a poor state of sanitation. It worsens during the rainy season when water forms nasty looking puddles that emit an offensive smell.
Ignored
The city authorities do not provide sanitation services in Kibera, and few landlords have constructed pit latrines for their tenants. Thus, the few available pit latrines are often overstretched. As a result, residents turn to any available means for disposing solid waste.
On the other hand, various projects and interventions that seek to solve sanitation challenges caused by the indiscriminate disposal of solid waste have not yielded good results. This is partly due to a rapid increase in population size and fast growth of the settlement itself.
Poor solid waste, drainage, and wastewater management, in addition to poor excreta disposal and inadequate water supply have contributed to high incidences of disease outbreaks. Common diseases experienced are diarrhea, typhoid, tuberculosis, and malaria.
Kibera is one of the largest informal settlements in Africa. Nairobi’s total population is estimated to be over 2.5 million. Among these, an estimated 60 percent live in slums, a third of whom live in Kibera. The over half a million residents of Kibera, like their counterparts in other slums in the city, do not have access to basic facilities.
Solution
To remedy the situation, Globology Limited teamed up two years ago with the NGO Umande Trust and Ushirika Roho Safi Laini Saba (Swahili for cooperating in good faith for the sake of Laini Saba), a community-based organization operating in the Laini Saba sector of Kibera. The partnership was aimed at finding a solution to the human waste disposal problem in Kibera. As a result, a simple, sustainable and innovative system for raw sewage treatment called the bio-latrine was introduced.
Through financial assistance from the Swedish International Development Agency (SIDA), the Nairobi Central Business District Association (NCBDA), and other stakeholders, a bio-latrine was constructed in the slum. An estimated US$ 250,000 was spent on constructing the facility.
Many Benefits
“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.
Consequently, the community is able to properly dispose human waste and at the same time reduce pollution and environmental degradation.
Ormiston said that 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 digesters and bio-latrines is that latrines use human waste instead of animal waste.
The toilet facility and digesters are constructed using conventional building materials and require little maintenance.
The systems are scaleable and can thus cater for various sizes of populations, ranging from small settlements to large institutions.
“They are ideal for both urban and rural schools and health centers where cooking energy is required,” said Ormiston.
Structure
The 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.
Ormiston explained that choosing the size of the bio-latrine is based on the fact that the sludge must remain in the system for at least 120 days. This is to ensure that the sewage is well treated and rendered harmless by the time it leaves the system.
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.
The number of appliances that a single latrine can supply depends on the number of people using the latrine and the size of the digester. A larger number of users and a big of digester will produce more gas. Ormiston pointed out that despite the huge potential of this technology, it takes five people depositing all of their urine and feces in a latrine to produce enough gas for one hour of light or domestic cooking.
According to Globology limited, the most efficient use of the gas is the generation of heat for cooking, hot water heating, laundry irons and powering refrigerators. The gas can also be burned to create light.
An important way to utilize the 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. To cash-strapped communities, this is a hindrance since sourcing and proper installation and running of generators might prove to be a challenge.
The sludge from the bio-digester is fed into one or the various interconnected expansion chambers (the number of chambers depends on the size of the system), which are also underground, but at a higher level. The sludge exits the system mostly from the expansion chambers via a pipe leading into the holding tank, where it can be harvested for use as fertilizer.
Maintenance
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| The toilet facility and digesters are constructed using conventional building materials |
Operating and maintaining the bio-latrine is simple given that it has no moving parts. The only rule to observe is that apart from human waste, the only other allowable material to enter the system is toilet paper.
For the Kibera Laini Saba community, where the bio-latrine is located, those who manage the latrine ensure that toilet paper is issued to users as they enter the latrine so that they do not use other materials like plastic. The usage of the latrine, which was built to accommodate 600 to 1000 people a day, has been increasing from less than 400 people at inception to over 500 a day.
Onesmus Nyamai, chairman of Ushirika Roho Safi Laini Saba community group, said that they levy a minimal fee to shower and toilet users to enable them to purchase toilet paper and pay the attendant who manages the facility.
Serving the Community
Nyamai’s group was started a decade ago to address problems facing the community such as poor sanitation and lack of access to clean water. This had led to exploitation by water vendors, who were collecting approximately US$ 11 a day from the locals.
“We are very careful with the charges we levy toilet users and the category of people we charge for the service, because if the amount of money charged deters large scale usage of the facility, then we will not be able to generate enough gas,” said Nyamai. He added that the amount charged depends on household income and that needy cases pay little or no fee at all.
Aloice Ogutu who uses the facility is pleased with project. “The bio-latrine technology has improved the sanitation of this place. Previously raw sewage used to flow in front of our doorsteps but the situation has improved,” he said.
The gas from the bio-latrine is used for lighting and cooking for over 50 orphans in a school located close to the facility and run by the community-based organization. The group intends on supplying surplus gas to nearby households for a fee, since the gas that is produced daily is more than the capacity required by the school. Currently it is only the school that is being supplied with the gas.
He said that they are yet to find a viable market for the fertilizer from the bio-latrine and they are liaising with the Nairobi Central Business District Association to secure a market for the product.
Nyamai urged the government to spread the technology to all informal settlements in Nairobi, adding that the bio-latrine technology is not only appropriate for informal settlements in urban areas, but also ideal for rural settlements and boarding schools. Rural farmers can effectively utilize the fertilizer generated and ensure food security.
Future Plans
Nyamai said that his group, which runs various sanitation programs in the slum in collaboration with NGOs despite lacking finances, would like to improve both human waste and garbage management. This could be done by increasing the number of bio-latrines, drilling a borehole for clean water provision, and installing an incinerator that will generate power to run light industries such as bakeries. Such projects will generate income to the group’s members, three quarters of which are women. They will also provide employment opportunities, he stressed.
“We have consulted the United Nations Environmental Programme (UNEP) for funding but the problem is lack of land where these projects will be located,” said William Misati, the group’s project clerk.
The issue of land in Kibera is sensitive because the informal settlement is legally recognized as government land. Also, much of the land has been allocated informally to structure owners who only legally own the structures on the land and not the land itself.
As a result, long-term projects to improve the lives of residents are hampered because the donor community has a tendency to demand that communities benefiting from the projects they fund show proof of security of tenure for the land on which the projects are established.
“Our aim is to improve the lives of our people despite the numerous challenges,” said Misati.
The project has been hailed by many as a unique way of conserving the environment.
“The bio-latrine project would help us keep the environment safe and habitable. Besides improving sanitary standards, the project also helps in curbing the pollution of water systems, such as the Nairobi River, and also reduces the demand for more finite sources of energy,” said Wafula Nabutola, chairman of the Nairobi Central Business District Association.
Moreover, a majority of Kenyans both in rural areas and urban centers depend on wood fuel (charcoal and firewood) to meet their energy needs.
Widespread use of wood has contributed to deforestation, which in turn has led to reduction of rainfall and the drying up of streams and rivers.
As a result, the country has been reeling from a severe drought since late last year that has not only led to death of livestock but also starvation among communities residing in arid and semi arid areas. Therefore, large-scale use of alternative sources of domestic energy such as biogas will play a pivotal role in saving forests from depletion.
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