Biogas is a renewable energy produced by fermenting organic materials such as animal waste and agricultural residues under anaerobic conditions. As fossil fuels continue to deplete, biogas provides a sustainable alternative for cooking, lighting, and power generation, helping to address the growing energy crisis.
What is Biogas?
Organic matters such as animal and human excreta, agricultural and industrial waste, water hyacinth, etc., when fermented under an anaerobic condition produce a combustible gas called Biogas.
It is a renewable source of energy, can be used as fuel for cooking, lighting, running vehicles, and generators, etc. Other natural resources like oil, gas, etc., are limited and will be exhausted in the course of time.
With the present rate of consumption, natural energy resources like gaswill be exhausted shortly, and it is high time to derive policy and practice for the exploration and use of alternative renewable sources if we want to meet the energy crisis in the near future. Biogas has been found to be a proven renewable energy option.
Types of Biogas by LGED:
There are three types of basic designs of biogas plants tried in Bangladesh:
- Floating cover digester,
- Fixed cover digester, and
- Plastic cover digester.
Floating cover digester:
It works on the principle of constant pressure, changing volume. The digester, cylindrical well, commonly made from brick and cement, is covered with a floating steel cylinder with an open bottom. As the cylinder has a constant weight, it moves up when gas production is higher than consumption and comes down under the reverse conditions.
Fixed cover digester:
It works according to the principle, constant volume, changing pressure. When the rate of gas production is higher than that of gas consumption pressure inside the digester rises and expels some digester contents into the outlet compartment. When the consumption is higher than production, pressure inside the digester falls, and the expelled materials in the outlet compartment run back to the digester.
Plastic cover digester:
A long cylindrical polythene/PVC bag, half-buried longitudinally in the ground, is fed with fresh cow-dung slurry at one end and discharged at the other. With the formation of gas, the bag swells like a balloon and the gas is led out to the point of use through a pipe by putting pressure on the balloon form outside.
In early 80’s, the floating type design was used for biogas plant. But due to corrosion of the steel dome, the gas leakage problem happened and it could not be removed. Later on BCSIR tried with fixed done type design and it has been successful in all biogas plants. The plastic bag type design is not used in Bangladesh it is used in China. In this project, the fixed dome type design has been proposed.
