Small scale energy sources and plants:Biogas plant

Biogas Digestor in rural Zimbabwe. Image credit climatetracker.org

• To install a bio-gas plant, a pit is dug underground near to the kitchen the depth of which is determined by the size of the plant the family wants to build.
• Then a brick and mortar chamber is built or a used oil drum is inserted into the pit.
• At least three pipes are drilled into this underground unit.
• One is for occasionally pouring a little water into the fermenting chamber.
• The second one is for releasing gas into the air if it is not being drawn to the kitchen.
• The third is to direct the gas to the kitchen where it is used.
• A lid is placed at the top of the chamber.
• To produce the biogas, organic matter in the form of raw cow dung or green foliage of plants and crops is placed in the chamber.
• The lid at the top is tightly sealed.
• A little water is poured through one of the pipes.
• Valves for the other two pipes are closed.
• A process called anaerobic decay takes place on the organic matter, with biogas produced as a by-product.
• Through the safety pipe, one can smell that the gas is being produced and can now be used in the kitchen.
• When the organic matter no longer produces large amounts of the gas.
• The lid is opened and the organic matter is removed and replaced with fresh supplies.
• The removed, partially decayed matter can be used safely as garden manure.
• Tis is cheap, simple and environmentally friendly source of energy.

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