Prisons with a Green Solution
An ingenious solution is helping Rwanda to reduce the cost of running its bursting prisons while improving conditions for the prisoners and helping to 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 exists 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, beehive-shaped human manure digesters, a steady supply of biogas is on tap for cooking and lighting at prisons – Rwanda is the first country in Africa to do this. Five of the country’s largest prisons – two in 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.
Biogas is produced from the fermentation of household or agricultural waste or animal or human faeces and has become a viable alternative when traditional gas sources become more expensive. The waste is placed in a 150 cubic metre beehive-shaped digester and fermented until a gas is produced. According to lead engineer on the project Ainea Kimaro, 100 cubic metres of waste are turned into 50 cubic metres of fuel by bacteria devouring the manure in just four weeks.
The digesters are a project of the Kigali Institute of Science, 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 covers the costs of feeding so many prisoners.
Many would think that this is 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. – (February 2008)
Biogas plant under construction at Kitarama prison, Rwanda.