Flush toilets connected to dome-shaped bio-centers are turning human waste into low-priced biogas used for cooking in some of Nairobi's sprawling slum areas.

"We expect the centers to improve sanitation, provide renewable biogas and reduce greenhouse gas emission," Elekta Rosana, bio-system engineer for the centers, told Anadolu Agency.

The bio-centers – with include communal flush toilet – have been set up by Umande Trust, a local NGO, and several partners with funding from local banks.

The cost of setting up a single bio-center is estimated at around $22,500, while people pay three cents every time they use a toilet.

"The equipment we have installed in all our centers divert human waste into a digester that automatically generates biogas – natural gas – that residents of this area use for cooking in gas stoves," said Rosana.

She explained that the flush toilets are connected to strong plastic pipes, linked to a dome-shaped holding tank and a bio-digester.

When human waste from the toilets reaches the tank, said Rosana, it is broken down in three stages by anaerobic bacteria.

"In the first stage, bacteria converts the waste into liquid, [then] the liquid is filtered and converted into acid," she explained.

"In the third stage, the liquid is retained for 21 days before turning into methane gas, which collects at the top of the dome tank," added Rosana.

The engineer went on to point out that, at this stage, the gas is piped to dozens of stoves in communal kitchens, where it is used for cooking, and sold to local residents.

The bio-centers are the brainchild of Josiah Omotto, the director of Umande Trust.

"We decided to set up the centers because informal settlement areas in Kenya had many pit latrines," he told.

"Because the slums are densely populated, the latrines have always been full," noted Omotto, who blamed the problem on the owners of sewage exhauster trucks.

"They [truck owners] charge between $100 and $150 to empty a latrine. Poor communities living in slums cannot afford to pay this money," he explained.

"What follows is a spillover that takes the waste to the ever-murky neighboring Nairobi River," he added.

Official statistics from Kenya's Ministry of Land, Housing and Urban Development show that access to water and sanitation is extremely limited for some 60 percent of Nairobi's roughly four-million-strong population.

-Multiple benefits-

Omotto says the bio-centers serve local communities in Nairobi and especially in Kibera, a sprawling area of rusting tin-roofed mud houses, dilapidated – and often muddy – roads, narrow alleys and slime-filled ditches.

He noted that a family of six now spends some $5 a month on biogas for cooking, compared to four bags of charcoal – worth $90 – for the same period.

Fredrick Amwok, the NGO's community organizing officer, stressed that one of the aims of Umande – which means "dew" in the local Kiswahili language – was to ensure that human waste no longer littered the streets.

"The environment in the slums is gradually becoming cleaner," said Aidah Binale Ibrahim, program coordinator for the NGO.

"Before the advent of biogas, we had flying toilets," she said, referring to plastic bags in which people defecate and then discarded in the alleys outside their shacks.

Kibera slum, which is home to nearly one million people, nearly half of them barely manage to eke out a living from small businesses, hosts the main two bio-centers.

Christine Otieno, a 36-year-old mother of four and a water seller, lives near one of them.

"I am lucky that where I am, we have flush communal toilets," she told.

"We no longer use those structures you see there," she said pointing at three disused shallow pit latrines.

Jacob Atemi, a 53-year-old bicycle repairer who lives in a five-by-five-meter mud-walled ramshackle, is equally happy.

"The lives of people you see here have changed," he said.

"We live in these mud-walled houses but like people living in stone houses in high class residential houses in the city, we now have flush toilets," Atemi told with a smile lightening his face.

"I wish such facilities were established in the whole of Kibera," he said.

Anadolu Agency / Foto: Wikimedia