Bio Generator

Pius Sawa Murefu

Kampala, Uganda - Aug 2007

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Thanks to biogas technology that is here to stay, if adopted by Ugandans and Africa in general; a sharp decline in the use of non-renewable energy fuels could soon become a reality.

It requires only 15 kilograms of cow dung per day to provide light and heat for a home of up to 15 people.  Eighty percent of Uganda’s population are farmers and entirely depend on agriculture for a living.  Forty percent of the population live in extreme poverty, meaning they struggle to obtain basic requirements like food, shelter and clothing.  Less than twenty five percent of the population have electricity, and many children cannot study at night due to the high cost of fuel to light up lamps.  But one thing is for sure, most households can access animal waste.

The biogas generator requires three non-indegeous cows or five indigenous ones to produce 15 kilograms of dung that can provide for a family’s basic daily energy needs.

How it works:

The cow dung is mixed with water on a one to one ratio to reduce its acidity.  It is placed in a chamber called a digester within which a reaction takes place.  This reaction is called anaerobic digestion and it involves the decomposition of the cow dung in an airtight environment, thus enabling bacteria to break down the cow dung, releasing methane gas in the process.

The gas is then tapped through a pipe that leads to a condenser which removes any condensed water, essentially this process dries the gas.  The dry methane gas is now ready to be utilized for household needs such as cooking or lighting.  A multiple channel mechanism is required if several burners and lamps are to be powered from one generator.

The smallest unit sells for as little as 500,000 Uganda shillings which is equivalent to about $300.  This amount of money can pay a terms school fees for a student at secondary school. Other larger units that can serve a large family sell for up to 1.5 million Uganda shillings, just less than $1000.

It will take twenty days after the initial installation for the generator to start producing biogas.  After that, providing the units are regularly refueled, production is on a daily basis.  Cow dung is placed in the digester every morning, however prior to doing so it should be sorted to remove any foreign particles like stones and sticks.  The good news is that even chicken dung can be used.

According to Christopher Kato, the operations engineer at the biogas consultant engineering workshop in Kawanda, the cost of the unit includes fitting and construction expenses.  The domestic biogas generator is usually installed underground in a concrete housing.  The effluent from the generator is automatically ejected as the compressor pushes down the dung when gas is being used.

Environmentally friendly, this technology is a low cost replacement for firewood of which harvesting is one of the contributors to deforestation in Uganda.  Those using electricity who also want to utilize the technology will realize savings of up to 75% on their monthly electricity bills.  In such cases the gas would be used for light and heat, while electricity would be used to power radio, television sets and other such equipment that require electrical power.  Robust, the biogas generators require little maintenance apart from routine checks for any gas leakages.

Government involvement:

The ministry of energy has taken up the task to raise awareness about the technology to the rural poor.  At the moment only fifteen percent of the population are using biogas generators due to the fact that most people are not aware of them.

If the campaign is well received we shall expect to see a reduction in respiratory diseases caused by the use of kerosene tin lamps.  Uganda’s vice president Professor Gilbert Bukenya has launched a campaign against tin kerosene lamps which he says are detrimental to health.  Being a medical doctor he says he has carried out postmortems on people and found that their lungs produce black liquid.  He attributes this to in-hailed smoke from kerosene lamps.