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Saturday, 21 August 2010

Cooking Biogas and the Forests

Sub Saharan Africa has a large population growth with ever increasing demand for fuel for cooking and heating. But people cannot just throw a switch and get electricity or turn a valve and get natural gas. They have to rely almost entirely upon wood and charcoal.
Charcoal is produced by driving off the water in wood by slow heating in the absence of air.
All over Uganda you will see people carrying huge sacks of charcoal and it is sold all along the main roads through the country.

This is resulting in a dangerous reduction in forest and the desert lands of the Sahara are moving south and taking over good farmland and dead forest regions.
One solution which has been used extensively in India and Pakistan is the use of methane gas for cooking. The methane, referred to as Biogas, is created naturally by the breakdown of vegetable and waste organic materials. The gas produced is about 75% methane and 20% carbon dioxide plus some other impurities. Untreated is cannot be used for fuelling motor cars but it can be used for cooking and for lighting.
Andrew Ssempiija Director of St Zoes has developed some real enthusiasm for this and with help from Makerere University he built the first school biogas plant on 2008.
It meant rebuilding all the school toilets so that this waste plus other animal waste can gravity fall into two underground concrete digester tanks.
The gas starts to be created very quickly and St Zoes is now able to provide enough for nearly all the cooking for over 500 people each day from biogas. There is no smell and and the other byproduct from the biogas plant is a very good fertiliser liquid.

                                
This illustration gives a good idea of how it works.
One of the special skills courses which have already started at St Zoe is to teach local farmers how to build their own domestic biogas plants and already we have done about 6 of these. The benefits to the ecology are clear. But the benefits to the people are in not having to buy charcoal or kerosene which are huge benefits.

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