Prisons with Green Solutions
An ingenious solution is helping Rwanda reduce the cost of running its bursting prisons, while improving conditions for the prisoners and helping protect the environment.
The country’s prison population soared to a peak of 120,000 suspects awaiting trial for their role in the 1994 genocide, in which 800,000 Tutsis and moderate Hutus were killed. The traditional court system, gacaca, is being used for national reconciliation, but the process is slow and costly for a country where 90 per cent of the population exist on subsistence agriculture, and where food production has dropped below 70 per cent of the levels needed for self-sufficiency (USAID).
But thanks to enormous, bee-hive shaped human manure digesters, a steady supply of biogas is on tap for cooking and lighting at prisons – the first country in Africa to do this. Five of the country’s largest prisons – two at Gitarama and one each in Butare, Kigali and Cyangugu – now have biogas plants producing 50 per cent of the gas needed to cook for prisoners. It has also saved half of each prison's US $44,000 a year firewood costs. The money saved is being ploughed back into renovations to the prisons to improve conditions, and to provide more services like healthcare.
Biogas is produced from the fermentation of household or agricultural waste or animal or human feces, and has become a viable alternative when traditional gas sources become more expensive. The waste is placed in a 150 cubic meter beehive-shaped digester and fermented until a gas is produced. According to lead engineer on the project, Ainea Kimaro, 100 cubic meters of waste is turned into 50 cubic meters of fuel by bacteria devouring the manure in just four weeks.
The digesters are a project of the Kigali Institute of Sciences, Technology and Management ‘s Center for Innovations and Technology Transfer.
“Biogas kills two birds with one stone,” Kimaro told the BBC. It gets rid of all the human waste and helps cover the enormous costs of feeding so many prisoners. Prior to the digesters, the quantity of human waste was a real problem: it was flooding down hillsides and leaking into rivers and lakes.
A school, the Lycee de Kigali , also has a digester. “The methane gas is used to cook for 400 students and for operating Bunsen burners in the school laboratories”, Kimaro said.
Many would think this a smelly affair, but in fact the whole process isn’t that pungent. Most of the digester is underground and the gas produced burns a clean, blue smokeless flame. It is much cleaner than the smoke from firewood. The remaining sludgy residue is used as an odourless compost for soil. This is used in the prison gardens to grow maize, mangos, bananas and tomatoes – all of which ends up back on the prisoner’s plates, improving the quality of their nutrition.
“The firewood savings are excellent - they really make a difference for us," a Cyangugu prison warden said, adding that the odour-free compost had done wonders for the prison gardens. "Look at all these bananas! This fertiliser really is the best," he said to the BBC.
In Uganda, human urine and feces are being mixed with banana peels, algae, water hyacinth and poultry droppings to make biogas. In Uganda’s rural Mukono district, biogas is used for cooking, lighting pressure lamps and to power engines. The slurry left over is then used to fertilise the soil. For Ugandans, most of whom are rural dwellers, electricity is rare and petrol to run generators and refrigeration units is expensive.
“It keeps the environment free of organic wastes, is convenient, time-saving and reduces smoke-related illnesses often associated with the use of firewood," said Patrick Nalere, country director of theHeifer Project International, an American NGO which shares livestock and knowledge to reduce poverty. "If the majority of Ugandans adopted biogas, we would preserve our biodiversity. People should exploit decomposing raw materials, which are free. Therefore, no monthly power tariffs.”
- Practical Action has technical drawings and guidelines for making a small biogas digester.
- The Anaerobic Digestion Community: Here is an excellent technical explanation of how a digester works, including a short film.
- China is boasting a fast-growing biogas economy using farm waste. Here is a full summary of their experience: http://www.i-sis.org.uk/BiogasChina.php.