Bio-gas, a neglected resource with huge potential

Very often when we think about Renewable energy sources, solar and wind energy technology come to mind.  There are many other technologies, that have perhaps not kept pace with the development with wind and solar, but are vitally important for the energy network of the future.

One such resource that has tremendous potential is bio-gas. While its use is prevalent in western Europe and US, it is under utilised in the developing world. This is ironic because Bio-gas can be generated free of cost. Interestingly, the plant needed for Bio-gas generation can be made for as low as 250 to 300 dollars. This plant can produce enough gas to meet the cooking requirements of a family ( three meals a day) and also run a lamp during the night.

The feed for the tank is animal manure.  The waste generated from 4 to 5 animals (cattle), is enough for a family of four. Additionally, the waste from the household toilet can also be used to supplement the animal manure.  Some waste water is also mixed to help the manure breakdown and flow.

The plant is essentially just three chambers, two are open while a third one is closed with a dome shape structure. These chambers are dug in the ground. The dome can either be constructed out of metal or made out of Ferro cement. The idea is to hold the manure for a time period while it breaks down and digestates. This produces methane or natural gas. The gas gets collected in the dome chamber and  can be tapped out of the chamber through a pipe connected at the top of the dome. There is a pressure gauge on the pipe to indicate the pressure of the gas and a valve that allows the release of the gas.

In many countries where ambient temperature reaches 20-25 degree centigrade, the process of manure breakdown is quicker as compared to colder countries. Once enough gas it generated it pushes out the remaining manure which has turned into slurry. This slurry can be dried and can be used as organic fertiliser or can be mixed with compost.

Bio-gas plants have turned around the lives of many families in rural areas. The gas is used for cooking. It burns without smoke and does not produce any smell. Bio-gas has replaced the need for burning wood sticks, which would require chopping down trees. In subcontinent, the practice of burning dried cow dung cakes is very common. These dung cakes are burned in homes for cooking. They release smoke that result in several respiratory diseases but is also damaging to the environment. With Bio-gas, the practice of using cow dung can be eliminated entirely.  Gas lamps can also be used during the night for light. Flickering light from candles is not good for the eye sight particularly for those who would like to study in the dark hours. Through Bio-gas however, stable light can be produced via gas lamps.

Bio-Gas Plant diagram

Bio-Gas Plant diagram

It has been estimated that a single small plant, which does not occupy an area of more than 20 x 6 feet can cater the energy needs for a family in the village. It can potentially save 2-3 tons of wood per family per year. The gas can also be used to run a generator, that will produce electricity.

Awareness about Bio-gas plants needs to be increased.


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