Which material is most commonly used for the generation of biogas?

Biogas is a renewable source of energy produced by the breakdown of organic matter in the absence of oxygen, a process called anaerobic digestion. The main raw material used for this process is animal waste, particularly cow dung, because it is widely available, rich in organic matter, and produces a high yield of biogas.

When animal waste is fed into a biogas digester, microorganisms decompose the organic matter and release a mixture of gases. The primary component of this gas is methane (CH₄), which is a highly combustible fuel. The biogas mixture also contains carbon dioxide (CO₂), a small amount of hydrogen, and traces of hydrogen sulfide. Methane is the most valuable part because it can be used for cooking, lighting, heating, and electricity generation.

Now, looking at the options:

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  Animal wastes (Correct Answer): They are the most widely used input for biogas plants across rural areas worldwide. Cow dung, buffalo dung, and poultry litter are especially effective.

  
  


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  Forest residues: While leaves, branches, and wood residues can decompose, they are not the primary source for biogas production, since their lignin-rich content makes decomposition slower.

  
  


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  Aquatic plants: Some aquatic plants like water hyacinth can be used, but they are less common and not as effective as animal dung.

  
  


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  None of these: Incorrect, because animal wastes are indeed a common material for biogas.

  
  

The use of animal waste for biogas production also solves the problem of waste management, reduces dependence on firewood, and lowers deforestation. Additionally, the leftover slurry from the biogas plant is an excellent organic fertilizer rich in nitrogen, phosphorus, and potassium, improving soil fertility.

Thus, the correct answer is Animal wastes, which remain the most common and effective raw material for biogas generation.