Biogas project helps school to save money and environment
When Evelyn Mukami, a Form Three student, joined Gachoire Girls' Secondary School in Central Kenya in January 2010, she was surprised to learn how meals were prepared.
Charcoal and firewood that are typically used for cooking in Kenya were nowhere to be seen. Instead, the kitchen used biogas produced from the students’ own toilet waste to cook.
“Before I came to this school, I was living in Nakuru where we use charcoal and firewood for cooking,” Ms Mukami said. “I didn’t imagine my waste being a source of energy.”
Since 2006, biogas has been a key source of energy for the 36-year-old school, saving it the expense of buying fuel and emptying latrines while also preserving a significant number of trees and reducing carbon dioxide emissions from burning wood.
In the process, Gachoire has become a model of how effects of climate change can be mitigated at the local level
“If all schools took up this initiative, after a few years we can count how much carbon we have saved from the atmosphere by sparing the trees and our forests,” said Ms Esther Lung’ai, a project officer at the Arid Lands Information Network, a non-governmental organisation.
Ms Lung’ai added that she had eaten food from the school kitchen and there was nothing in its taste to indicate that it had been cooked using by-products of human waste.
Waste from toilets at the school is deposited into large pipes and pumped into a bio-digester buried underground.
Bacteria are added to break down the waste, and gas is produced as a by-product of the process.
A pipe transfers the gas from the digester to the kitchen, which is about 200 metres away. When the bio-digester is full, excess water and waste go to other chambers called breeders.
As gas is used up, the water and waste in the breeders return to the digester for further processing. After the waste has been fully digested, remnants are stored in tanks from which they can be collected and dried to produce fertiliser.
Mr Peter Muraya, a teacher who was involved in the project from its inception, said the bio-digester was built with the school’s planned expansion in mind. It has a volume of 21,000 litres.
“When we started we had around 600 students,” Mr Muraya explained.
“But now we have 849 students and the number is increasing. The bio-digester is large enough to supply the gas to the kitchen for all the children’s needs, he said.
The Gachoire Girls' Secondary School biofuel project was initially funded by the European Union.
The project is saving wood that would otherwise be needed to cook school meals. Mr Muraya said that previously, the school bought three lorry loads of firewood for each term.
“That was 21 tonnes of firewood, which would translate into 50 mature trees,” said Mr Muraya. This means that the school is now conserving 150 mature trees every year.
The school’s principal, Ms Naomi Njihia, said the energy saved it more than Sh10,000 each month on fuel.
“It is very helpful,” said Mrs Njihia. “The school has also saved money by (not having to empty) the pit latrines.”
Mr Samuel Githumbe, a school cook, said that cooking with biogas had a number of advantages over firewood.
“This gas is very fast,” he said.
“If you have a big number of people to cook for, the work is faster, you don’t waste time splitting firewood. Besides, the gas does not produce smoke that is dangerous to health.”
Mr Githumbe, who was born in the area, said he had seen negative consequences of using fuel wood. He said the climate of the area was different from when he was young.
‘‘The hills are treeless, cleared for firewood, farming and construction by the growing population,’’ he said. This has allowed strong winds to destroy crops, while floods wash away the soil during heavy rains, he said.
The school has been able to preserve four acres of its own woodland that without the biogas project would eventually have been felled for fuel.