Bio gas: A school is using a latrine to cut its energy bill

Wednesday November 05 2014
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Above, a stove at Kansanga Primary School. The stove uses bio gas produced from a bio latrine using human and animal waste. Photo by Michael Kakumirizi

A school in Kansanga, a suburb in Kampala, has found a way of minimising the bills they pay for energy while reducing their carbon footprint, all with the help of a latrine.
Kansanga Primary School has a bio-latrine, which if widely developed, has the potential of turning organic wastes into sources of clean energy that can save the country’s forest cover and also minimise on air and water pollution.
The bio-latrine, which the pupils use, also supplies cooking energy to the school. The school uses human waste and cow dung to generate biogas – gas produced from decomposing material.
This is opposed to common sources of biogas, cow and pig dung known to many.
According to Musa Busa Mwima, the school head teacher, the administration has managed to cut down on the amount of fire wood consumed while preparing food for the more than 900 pupils.

The benefits
“Economically, it [the bio-latrine] produces biogas which we use to cook food and porridge. It has reduced the expenditure from Sh2.8m normally used to purchase four lorries of fire wood to Shs1.3m, for one-and-half lorries,” says Mwima
With biogas, the headteacher says it takes about 30 minutes to cook dry beans as opposed to one hour when firewood, which has lots of smoke, is used.
He adds that the technology is very effective in cutting down hydro-power bills if developed to power lighting,and mitigating carbondioxide emission. Meanwhile, the school is considering using bio gas to power the security lights in the near future.
“When there is shortage of human waste, we buy a lorry of cow dung from the city abattoirs and animal farms at Shs300, 000. This can help generate gas for a four-month term,” Mwima says.
Mwima says the school has been challenged by lack of stoves due their high costs, one used to prepare food for about 1000 people costs around shs1.5million.
“The school has just purchased one stove to complement the small stove currently used to cook for about 450 pupils,” says Mwima, adding that the gas generation depends on the number of people using the bio-latrine.
Edna Nyamwaka, a biogas chief engineer based at Heifer International, a nonprofit organisation that promotes the technology among dairy and piggery farmers says for each biogas digester constructed, two hectares of forest cover are saved and about 20 tonnes of carbondioxide are avoided.
Biogas use does not only provide a clean cooking environment free from smoke, it also reduces on in-house pollution in form of charcoal or fire wood smoke. The kitchen at the school is not any different from an ordinary one. Its tiles look sparkling white and the wall paint has remained unstained making, a testament to the no-smoke advantage of bio gas.

According to Nyamwaka, an urban household with access to animal and organic can afford a unit of biogas, considering that digesters are made in different sizes. A four-cubic-metre digester can use one-and-half basins of dung to generate energy enough for up to two hours of cooking and lighting.

Beyond this school
Currently, through Uganda Domestic Biogas programme, Heifer international has supported the constructions of digesters in more than 6,079 households in Uganda. Nyamwaka says a bio-latrine at Kansanga Primary School costs between Shs35m and Shs40m, with the smallest biogas unit of four cubic metres costing about Shs1.5m.
“To dairy farmers, biogas is cheaper and accessible since it’s generated from raw materials that are freely available to them,” says Nyamwaka.
“The process of generating the gas produces a by-product known as bio-slurry which is an excellent organic fertiliser for all types of crops. The slurry can be applied to farmer’s gardens to boost crop yields and also develop animal feeds for pigs, goats and chicken,” adds Nyamwaka.

Why it is important
A recent report by the Inter-governmental Panel on Climate Change (IPCC) cited unprecedented increase in the global warming rate caused by human activities.
The main activities causing climate have been identified as greenhouse gas emissions, burning of fossil fuels, extraction of minerals, deforestation and mushrooming urban settlements in Africa among others.
The report highlighted that the first decade of this century [2001-2010) was the warmest since 1850 and for Uganda, it indicated that rain patterns in Uganda have become increasingly unpredictable.
According to George Mugerwa, the programmes manager at Uganda Domestic Biogas project, the use of biogas and other clean energy like solar can help in addressing deforestation and land degradation caused by the quest of the rural population in accessing charcoal and firewood.
Uganda has hand its share of climate change, evident through the landslides in Bududa, the bursting of river Nyamwamba banks in Western Uganda, the melting of snow at the highest peaks of the Rwenzori ranges, the flooding of roads in Kampala city, change in rainfall seasons in across the country.
Environment activists have been demanding that industrialised economies which are the largest contributors of greenhouse emissions should fund clean energy projects in Africa as a way of migrating climate change.

Proper policy needed
Speaking at one of the Climate Change dialogues organised by the France Embassy in Uganda, the deputy director of the Advocates Coalition for Development and Environment Onesmus Mugyenyi, noted that there should be policy formulation, institutional reforms and programmes that provide developing countries with financial incentives to reduce greenhouse gas emissions.
Recently, President Yoweri Museveni also said climate change is a new modern aggression against the always wronged African continent and its people. He, however, warned that such life threatening aggression against humanity should stop.
“The global threat by the North American, European and some of the Asian countries is through the release of carbon-dioxide into the atmosphere as well as the release of other gases that erode the ozone layer,” the President said while addressing 69th United Nations General Assembly during the Climate Change Summit held this year in New York.
When you factor in all the above, there is no denying that any effort no matter how small it seems, as is the case with the school in Kansanga, is important in the fight against climate change.


How the bio latrine works

Constructed by the support of the German International Cooperation (GIZ), the bio-latrine latrine differs from common pit latrines in terms of its usage and hygiene.
“It does not smell and doesn’t attract flies thus has worked for us in improving the pupils’ hygiene on top of being easy to use,” says Mwima.
The bio-latrine at a glance looks like a ventilated improved latrine (VIP) but operates like a modern flushing toilet. It requires little amounts of water to push the waste into a 30-cubic-metre digester, where decomposition takes place.
The digester made out of concrete acts as the pit but also produces gas which is dispatched trough a plastic tube to the school kitchen where it’s connected to a biogas stove. At this stage the tube can be connected to as many as four stoves ready for heating any food.