Kibera, the largest informal settlement in East Africa, rests five kilometres from Nairobi’s city centre and houses more than a quarter of the capital’s population. Defined by its uncertain land tenure, inferior infrastructure and low incomes, it is no secret that this densely populated area suffers from dangerously low levels of sanitation services.


According to an Impact Assessment Report conducted by Jean Africa Consultants (JAC), there is one pit latrine for every 50 to 500 community members living in Kibera. Often times, the location of a pit latrine makes it inaccessible for waste collection and after it overflows with excrement, it is abandoned. This results in the increased use of “flying toilets,” a plastic bag used for defecation that is tossed as far away as possible.

In Kibera’s Silanga Village, a survey conducted for the previous assessment report found that more than 50% of respondents admitted to throwing their waste using the “flying toilet” approach. The lack of plumbing and sanitation infrastructure perpetuates environmental degradation as all uncollected refuse ends up in the drainage trenches, river valleys and eventually into the Nairobi Dam.    

Communities in Kibera tend to be ignored by municipal authorities, who find themselves overwhelmed by the informal sector’s sheer numbers and needs, which far outstrip the capacity of local planners and government. Fortunately, a local NGO, known as Umande Trust, has stepped in with a project that fills the detrimental gaps in the waste management cycle by turning the excrement into a resource.   

Umande’s Bio Sanitation Initiative ensures that human waste is turned into wealth by producing gas, as well as a fertilizer by-product, through a bio digester
system. This transformation takes place in the 22 bio centres dispersed throughout Kibera.  

“You rarely find ‘green’ spaces in Kibera,” said Integrated Urban Environmental Planning Officer, Benazir Omotto. “[At the bio centres] community members can access low-cost sanitation while promoting the use of clean energy at nearby schools and businesses, even in individual homes.”  

A bio centre is a multi-story facility with three basic levels. The underground digester makes up the foundation of the centre. Human investment (waste from
ground floor toilets) is directed into a dome, which goes through anaerobic digestion and produces biogas as well as liquid fertilizer. The biogas is piped to
participating institutions such as schools, hotels and surrounding homes. A portion of the biogas is also delegated to power an on-site kitchen, which is available for community member use. 

“A school lunch program can burn over 14 tons of fire wood in a three month term,” said Omotto. “The kitchens [powered by biogas] allow the schools to boil huge pots of water and prepare large quantities of food in a manner that is significantly more energy efficient.”

A bio centre caretaker lights the biogas beneath a community stove

On the ground floor there are two bathrooms, for both male and female, with four toilets on each side. Customers enter at this level and pay a small fee to the caretaker in order to access the buildings features, including the previously mentioned kitchen.

The third and final floor houses space available for rent. Community members have the opportunity to lease the rooms for various purposes like recreation centres, school libraries or business offices.

“Working in urban areas, we find that there is not much space for recreation or community meetings,” said Omotto. “We encourage groups to make use of the upper floors in hopes that it will promote community action and advocacy, while subsidizing the rates of sanitation at the lower level.”

Community empowerment aside, Umande has come across a technical malfunction that severely inhibits the productivity of the bio centres. Each centre is built for a maximum capacity of approximately 500 users per day. However, because of the high demand for clean sanitation facilities in Kibera, over 1,000 people are being serviced by the centres in a single day. Exhausting the underground digesters to this degree causes them clog, rendering them incapable of processing the waste. Biogas cannot be produced and even the toilets themselves can no longer operate.

In order to combat this issue, Umande has partnered with the Nordic Environment Finance Corporation (NEFCO) and Niras, a Danish consultancy company, to construct a biogas plant. Based on Umande’s existing bio centre model, this plant will receive and process the excess waste from the bio centres and turn it into bottled biogas and fertilizer.

The project will begin by purchasing and operating an evacuator truck of 10 m3 capacity to service the active bio centres, remove waste surplus and deliver the end product/waste to the bio plant. Then, the evacuated waste, or biomass, will be emptied into a reception tank with a capacity of 80 m3  – allowing for five days of uninterrupted biogas and fertilizer production.

During this time, the biomass undergoes a process known as hygienisation to ensure all pathogens are killed. The hygienisation process involves retaining the
biomass at 70oC for at least one hour. This can be achieved by an array of three heated vessels, which will be operated so that they are alternate between being filled or being emptied. 

A bio plant simulation tests various temperatures during hygienisation 

Finally, the biomass is ready to be transferred into fertilizer and biogas. To create the fertilizer, biomass is combined with vegetable waste that has been collected and source-sorted from markets in Kibera. This mixture is known as a digestate. In order to produce a high-quality product, water must be removed from the digestate. Band filters will be used, where the digestate is deposited on a moving fabric, and the liquid drained off. The output from the band filter will be a peat-like substance with high content of phosphorous, and a liquid with most of the nitrogen in dissolved form.

“The remaining liquid will be taken to the Kenya Forest Service in order to irrigate much of the land,” said Bio System Engineer, Electa Rosana. “The solid matter
will be packaged and sold to local farmers as organic fertilizer.” 

The biogas is produced in agitated reactor tanks, called bio digesters, through the previously mentioned process of aerobic digestion. Biogas is then bottled on site, making it available for commercial use. This component of the plant is completely unique from the gas pumping that takes place at all other bio centres.

The goal is to transport methane gas to niche consumers in high pressure gas bottles or cylinders, as methane cannot be liquefied at ambient temperatures. The technology envisaged is similar to that applied for CNG vehicles, that is compression to about 2 MPa (200 bar).

“A number of gas and LPG companies have monopolized the market, making prices inaccessible to low income earners,” said Bio Technician Fanuel Ong’ato. “Now we
are coming in as competition. It will also compel them to improve on, not only price, but also the purity of the gas because we are creating a product that is better for the environment and better for you.”

The laundry list of bio plant benefits extends far beyond environmental and well into economical. All original bio centres are currently owned and operated by community members. The owners and staff will become shareholders of the bio plant because Umande will be using product from the centres to power the new bio plant.

“Since we’ve extracted the organic waste from the bio centres it means that each and every bio centre will be having a unit of ownership within the bigger plant
because the plant is owned by the bio centre network,” said Ong’ato. “Bio centre owners will also be entitled to a designated number of compressed gas cylinders and fertilizer bags that they can sell at kiosks in their centres.” 

An Environmental Impact Assessment Report was conducted and approved by the Environmental Management Authority to build the plant in Udongo, Kibera. Currently, Umande is finalizing designs, which will be taken to a county council for approval.

“Umande believes that modest resources placed within the community can go a long way in improving individual rights,” said Omotto. “The vision is societies will have access to basic urban sanitation as a right. This will not only enhance the sanitation but it will also make for a clean environment and improved livelihoods
in the community.”

Construction on the plant is expected to begin early in January 2015.

Leave a Reply