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, primarily methane (CH4), and digestate, a nutrient-rich fertilizer. It consists of a sealed, cylindrical tank partially submerged in a water-filled pit, with a floating dome or drum that rises and falls with the production of biogas. Here's an explanation along with a diagram:

Diagram of Floating Drum Biogas Digester:

             ___
           /  |  \
          |   |   |
          |   |   |
           \__|__/
            /   \
           |     |
           |  O  |    <- Floating drum
           |     |
           |_____|     <- Digester tank

Working Principle:

1. Digestion Tank: The main component of the floating drum biogas digester is the digestion tank, which is usually constructed from concrete or masonry. It is partially submerged in a water-filled pit to provide support and maintain a constant temperature.

2. Feedstock Input: Organic waste, such as animal manure, crop residues, or food waste, is fed into the digestion tank through an inlet pipe or chute. The waste undergoes anaerobic digestion, facilitated by microbial activity in the absence of oxygen.

3. Biogas Production: As organic matter decomposes, biogas is produced as a byproduct. The biogas, primarily composed of methane (CH4) and carbon dioxide (CO2), accumulates in the upper portion of the digestion tank, displacing water and causing the floating drum to rise.

4. Gas Storage: The floating drum serves as a gas storage chamber. As biogas accumulates, the drum rises, allowing it to float on the surface of the water. When the drum reaches its maximum height, excess biogas can be vented off or collected for use.

5. Biogas Utilization: The collected biogas can be piped out from the digester for various applications, such as cooking, heating, electricity generation, or powering engines. A valve or outlet pipe controls the release of biogas from the digester.

Advantages:

1. Simple Design: Floating drum biogas digesters have a relatively simple design, making them easy to construct, operate, and maintain, especially in rural or remote areas.

2. Low Cost: Compared to other types of biogas digesters, floating drum digesters are often more affordable to build and install, utilizing locally available materials such as bricks, concrete, or ferrocement.

3. High Biogas Yield: Floating drum digesters can achieve high biogas yields from various feedstocks, including animal manure, agricultural residues, and organic waste, providing a reliable source of renewable energy.

4. Efficient Gas Storage: The floating drum serves as an efficient gas storage mechanism, allowing for the accumulation and storage of biogas without the need for complex gas holders or storage tanks.

Disadvantages:

1. Limited Temperature Control: Floating drum digesters may experience temperature fluctuations, particularly in colder climates, which can affect the efficiency of anaerobic digestion and biogas production.

2. Risk of Gas Leakage: Improper sealing or damage to the floating drum can result in gas leakage, reducing the efficiency of biogas production and posing safety hazards.

3. Space Requirements: Floating drum digesters require a certain amount of space for construction and operation, limiting their suitability for densely populated or urban areas with limited land availability.

4. Maintenance Requirements: Regular maintenance is required to ensure the proper functioning of the floating drum digester, including inspection of seals, valves, and gas piping to prevent leaks and ensure efficient biogas production.

Despite these limitations, floating drum biogas digesters offer a cost-effective and sustainable solution for converting organic waste into renewable energy and fertilizer, benefiting both rural communities and the environment.