Explain floating drum biogas digester with neat diagram. Also write its advantages and disadvantage.

A floating drum biogas digester is a type of anaerobic digester used to convert organic waste into biogas, a mixture of methane and carbon dioxide, for energy production. It consists of a cylindrical digester tank, a floating gas holder or drum, inlet and outlet pipes, and an overflow pipe. The digester tank is buried partially underground, while the gas holder floats on the surface of the slurry inside the tank. The working principle involves anaerobic digestion of organic waste by bacteria, which produces biogas that accumulates in the gas holder, displacing the slurry and causing it to rise.

Construction and Working:

1. Digester Tank: The digester tank is typically made of concrete, brick, or plastic and is partially buried underground to maintain a constant temperature and provide insulation. It has an inlet pipe through which organic waste, such as animal manure, agricultural residues, or food waste, is fed into the digester.

2. Gas Holder: The gas holder is a cylindrical drum or dome-shaped container that floats on the surface of the slurry inside the digester tank. It is sealed to prevent gas leakage and connected to the digester tank via a guide frame or guide rails to ensure vertical movement.

3. Inlet and Outlet Pipes: Organic waste is fed into the digester tank through the inlet pipe, while digested slurry is discharged from the tank through the outlet pipe. The outlet pipe is positioned at the bottom of the digester to facilitate slurry removal.

4. Overflow Pipe: An overflow pipe is installed at the top of the digester tank to prevent overfilling and ensure proper gas storage capacity. Excess slurry or gas is released through the overflow pipe to maintain the desired operating level.

Advantages:

1. High Biogas Yield: Floating drum biogas digesters can produce a significant amount of biogas from various organic waste materials, including animal manure, crop residues, and kitchen waste.

2. Renewable Energy: Biogas produced in floating drum digesters can be used as a renewable energy source for cooking, heating, lighting, or electricity generation, reducing reliance on non-renewable fossil fuels and lowering greenhouse gas emissions.

3. Nutrient Recycling: The digested slurry, known as digestate, is rich in nutrients and can be used as organic fertilizer to improve soil fertility and crop yields, promoting sustainable agriculture practices.

4. Low Operating Costs: Floating drum biogas digesters have relatively low operating and maintenance costs compared to other renewable energy systems, making them suitable for small-scale and rural applications.

Disadvantages:

1. Space Requirements: Floating drum biogas digesters require adequate space for installation, including both the digester tank and gas holder. This may limit their feasibility in densely populated or urban areas with limited land availability.

2. Maintenance: Regular maintenance and monitoring are required to ensure proper functioning of the digester, prevent gas leakage, and address potential issues such as slurry overflow or gas holder malfunctions.

3. Initial Investment: While floating drum biogas digesters have low operating costs, the initial investment for construction and installation may be relatively high, particularly for larger systems or in regions with limited financial resources.

In summary, floating drum biogas digesters offer a sustainable and renewable energy solution for organic waste management and biogas production, with advantages including high biogas yield, renewable energy generation, nutrient recycling, and low operating costs. However, they require adequate space, regular maintenance, and initial investment, which should be considered when evaluating their suitability for specific applications.