C
CraftExam
medium difficulty6 min

Microbes in Biogas Production

Biogas production is the anaerobic breakdown of organic waste such as cattle dung by methanogenic bacteria, producing a fuel mixture rich in methane along with carbon dioxide and other gases.

In one line: Biogas needs three ideas together: dung slurry, no oxygen and methanogens.

Concept Practice Coming Soon

Understand it

  • Biogas plants use microbial activity in oxygen-free digesters.
  • Cattle dung slurry is a good substrate because it contains cellulose-rich organic matter and methanogens such as Methanobacterium, which also occur in the rumen of cattle.
  • In the digester, different anaerobic microbes break complex organic matter into simpler compounds, and methanogens convert these products into methane-rich gas.
  • The spent slurry can be used as manure.
  • CBSE questions usually focus on methanogens, anaerobic conditions, cattle dung slurry and the labelled structure of a biogas plant.

Example

In a rural biogas plant, cattle dung is mixed with water and fed into the digester. Anaerobic microbes act on the slurry, biogas collects in the gas holder or dome, and the digested slurry comes out through the outlet.

Rule to remember

Key biological rule: methanogens produce methane only under anaerobic conditions while decomposing organic substrates.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

  1. 1Question: Name the microbes involved in biogas production and state their condition.
  2. 2Answer: Methanogens such as Methanobacterium produce methane from organic waste under anaerobic conditions.

Method you can reuse

  1. 1Mix cattle dung with water to form slurry.
  2. 2Feed slurry through the inlet into an airtight digester.
  3. 3Anaerobic microbes break down organic matter.
  4. 4Methanogens produce methane-rich gas.
  5. 5Gas is collected and supplied through the outlet.
  6. 6Spent slurry is removed and used as manure.

Visual tip

Important labels: mixing tank, inlet pipe, digester tank, gas holder or dome, gas outlet pipe, overflow tank and spent slurry. Notice that the digester must remain anaerobic for methanogens.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is cattle dung useful in a biogas plant?

Think first, then show answer
Cattle dung is useful because it contains organic matter and methanogenic bacteria such as Methanobacterium. Under anaerobic conditions, these microbes help produce methane-rich biogas.

Common wrong answer

Methanobacterium needs oxygen to produce biogas rapidly.

Don't mix this up

Students often write that oxygen is required for methane production. Methanogens are anaerobic and work in oxygen-free conditions.

Exam tip

In diagram questions, label inlet, digester, gas holder, gas outlet and spent slurry outlet clearly, and mention Methanobacterium for the microbial role.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Asked through diagram labelling, role of cattle dung, naming methanogens, or assertion-reason based on anaerobic digestion.

Answer plan

Define biogas, name methanogens such as Methanobacterium, describe cattle dung slurry in an airtight digester, mention methane production, and label the main parts if a diagram is asked.
  1. 1

    Enough for 1 mark

    Biogas production is the anaerobic breakdown of organic waste such as cattle dung by methanogenic bacteria, producing a fuel mixture rich in methane along with carbon dioxide and other gases.

  2. 2

    Add for 2 marks

    Example: In a rural biogas plant, cattle dung is mixed with water and fed into the digester. Anaerobic microbes act on the slurry, biogas collects in the gas holder or dome, and the digested slurry comes out through the outlet.

  3. 3

    Add for 3 marks

    Biogas plants use microbial activity in oxygen-free digesters.

Practice

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