Wednesday, 23 May 2007


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Every once and a while 23 year old biology researcher Olatubosun Adeleke (Obayomi) of Nigeria pops up and provides us with an update on his pioneering work in Nigeria. Most recently he has sent us some pictures of his latest work of which we are most grateful.
Below is a brief report of his household scale biogas production system. He explains how it works in his own words.

Digester pictures 12&3 are the horizontal UASB digester based on Prof George Chan’s design.The digester featured here is approximately a 1m3 digester that is designed for domestic cooking.

Gas Storage: Because of the small size of the digester, the gas produced can be stored here directly without needing a storage balloon , but a bigger size will need one.
What its Made of: The digester is built from two 200 liter drums.

What it Runs on: The digester runs on kitchen wastes and cow dung . I have also experimented with human faces. The wastes are poured into the outlet pipe gently not to allow air in.
Cooker Stove Specs: The cooker I bought was an automatic one for LNPG but wont work forbiogas because of the Orifice, so have gotten a locally built one with an adjustable Orifice.Digester Pic 1 (48kb): Picture 1 shows the front view with inlet pipes, the main tank and the mini manhole.

Digester Pic 2: Picture 2 shows the manhole and outlet pipes clearly. This is the dorsal view.
The top of the digester has 2 gas ports with gas valve, with only one in use.
Digester Pic 3: Below the inlet pipe is covered with a bend and a plastic mesh. This is just for human sight.

Pressure Tank: Picture 4 shows the pressure tank, the need for this is that the kitchen is located at the second floor and the gas pressure will drop as it rises.
The pressure tank serves as both gas storage and pressurized cylinder. It is made of two cylindrical tanks . The bottom one a water reservoir and top one gas storage. Gas enters from its inlet gas valve (Right) which is always open.

The biogas being insoluble in water lifts the upper drum up. This works against gravity and the gas is kept under pressure, no matter the distance away from the main digester.
Once gas is needed for use the outlet valve (Left) is opened and released under pressure, letting
the upper drum move under gravity.

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