By Justus Wanzala
NAIROBI (Thomson Reuters Foundation) - As Kenya seeks new clean sources of energy, it has turned to the sun, the wind, the earth's heat and its organic matter.
Now it has its eye on an additional source of power: Human feces.
Abundant and easily accessible, human waste can be converted into biogas used for cooking or generating electricity.
With millions of people living in Kenya's slums, generating 4 million tonnes of faecal matter per year, according to official estimates, the potential for biogas generation is enormous, experts say. And the infrastructure for collecting the waste could help ease Kenya's sanitation problems.
But energy companies keen to invest in poo power face two big challenges: cost and disgust.
Sanergy, which was established in 2012, runs a network of small-scale sanitation centres in Nairobi's Mukuru slum. Their Fresh Life Toilets, each designed for 80-100 uses per day, are franchised to residents.
The waste from the toilets is collected regularly in sealed cartridges and taken to a central processing facility. There the waste is stored in special biodigesters where it breaks down and releases methane, which can be used as fuel.
The biodigesters also remove disease-causing pathogens, so the leftover matter can also be used as fertiliser.
One tonne of human waste produces about 0.6 cubic metres of biogas. Sanergy has already collected 2,700 metric tonnes of waste from Mukuru, creating 122 jobs in the slum.
Energy experts say that when completed, Sanergy's biogas plant will be able to generate 250 kilowatts of electricity.
"The project has great potential for lighting up the slum and providing affordable fuel for cooking," said Edith Karimi, head of communications and outreach at Sanergy. The company is also experimenting with generating enough electricity to sell back to the national grid.
Poo-to-power initiatives are already at work in some Kenyan slums as well as several schools, but projects such as Sanergy's - with bigger funding and wider aspirations - hope to bring the benefits to more of the population.
Kenya's slum residents have limited access to clean sanitation. Many either rely on public toilets, which are scarce, or dig their own pit latrines that direct waste into rainwater canals and rivers, tainting water supplies.
Alternatively, residents use "flying toilets" - small plastic bags filled with human waste that are tossed out of windows and left wherever they land.
By looking for ways to pull energy from poo, Sanergy and other companies also aim to help solve Kenya's sanitation problem.
Afrisol Energy, which is based at the Kenya Climate Innovation Centre at Strathmore University in Nairobi, is working in collaboration with U.S. company General Electric to build a bio-latrine at the Mukuru Kwa Njenga Primary School.
Scheduled for completion in December, the $100,000 toilet system will serve the school's 2,000 pupils and should generate 4.5 cubic metres of biogas per day. The gas will be used to heat water and create steam, which will run turbines to generate electricity for the school and surrounding neighbourhood.
Amos Nguru, CEO of Afrisol, believes human waste should be taken more seriously in the renewables sector. The biogas that poo generates - methane - has a much greater warming effect than carbon dioxide when released into the atmosphere, but if properly handled and stored to avoid leaks can still be a much cleaner alternative to carbon-based fuels.
"Kenya has the potential to generate 10,000 kilowatts per day from human-waste-derived biogas," he said.
COSTS - AND SOCIAL STIGMA
One obstacle to the uptake of the technology used to convert faeces to fuel is the high costs associated with installing large biogas digesters.
Nguru says that universities and research institutions have not been aggressive in steering research towards biogas-generation technologies and "small companies lack the financial capabilities."
Financial institutions are also reluctant to fund ventures for biogas generation because they perceive the sector to be too risky, he said.
But Caesar Mwangi, Africa regional director at the Global Village Energy Partnership, which is involved in increasing access to renewable energy in developing countries, believes human waste could play a large role in helping poor countries meet their energy needs.
"Human waste is ignored due to stigma but it is ideal for high population density areas with low incomes and hence low access to grid electricity," he said.
However, supporters of poo power still need to overcome the ick factor. Afrisol's Nguru said that when he began promoting human waste as a source of biogas, many thought it was a joke.
"It seems I was venturing into a forbidden area or going against a taboo due to the cultural perception about human waste," he said.
At the Kenya Climate Innovation Centre, experts are working on promoting acceptance of human waste-based biogas projects. But all of their efforts will be wasted, said KCIC technology analyst David Ngugi, if they can't convince Kenyans that poo can pay.
"Most of the projects are based in the slums where residents are used to 'flying toilets'," he says. "They do not see their waste as having value."
(Reporting By Justus Wanzala; editing by Laurie Goering)