Q.What is biogas mainly composed of, and which group of microorganisms is responsible for its production from organic waste?

Showing the 12 most recent of 13 on this concept.

1. CBSE 2025Set 57/5/11 markMCQ
   Q.Assertion (A) : Biogas plants are more often built in rural areas. Reason (R) : The excreta or gobar of cattle is rich in Methanobacterium.

   ›Reveal solutionSolution

   The key idea is that biogas plants are set up in rural areas because cattle dung (gobar) is abundant there, and this dung naturally contains Methanobacterium bacteria that produce methane. Both the assertion and reason are true, and the reason correctly explains the assertion.

   Concept and Intuition

   Biogas is a renewable energy source produced by the anaerobic digestion of organic matter. The process relies on a group of bacteria called methanogens, particularly Methanobacterium, which break down complex organic compounds in the absence of oxygen to release methane (CH₄) and carbon dioxide (CO₂).

   In rural India, cattle rearing is widespread, so cattle dung (gobar) is readily available and cheap. This dung is rich in organic matter and naturally contains Methanobacterium bacteria. So the reason — that cattle excreta is rich in Methanobacterium — directly explains why biogas plants are more often built in rural areas: the raw material (dung) and the microbes needed are both locally available.

   Watch out

   A common mistake is to think that Methanobacterium is added to the dung. In reality, these bacteria are already present in the gut of cattle and hence in their excreta. The biogas plant simply provides the right anaerobic conditions for them to multiply and work.

   Step-by-step Reasoning

   1. Understanding the Assertion (A):

      Biogas plants are indeed more common in rural areas. Why? Because they need a steady supply of organic waste — and in villages, cattle dung is abundant. In cities, such waste is scarce or expensive to collect.

   2. Understanding the Reason (R):

      The excreta (gobar) of cattle is rich in Methanobacterium. This is a true biological fact. Methanobacterium is a methanogen that lives in the rumen of cattle and is excreted in their dung. It is the key microbe that converts the organic matter in dung into methane gas.

   3. Connecting A and R:

      The reason directly supports the assertion. Because cattle dung is rich in Methanobacterium, rural areas — where cattle are plentiful — have both the raw material and the necessary microbes to run biogas plants efficiently. Without this microbe, the dung would not produce methane in useful quantities.

   4. Evaluating the logical relationship:

      • Assertion (A) is true.
      • Reason (R) is true.
      • R is the correct explanation of A.

   Tip

   Think of it this way: a biogas plant is like a "digester" that needs both food (dung) and the right "chefs" (Methanobacterium). Rural areas provide both naturally. That's why they are the ideal location.

   ✓Final answer

   Both Assertion (A) and Reason (R) are true, and (R) is the correct explanation of (A).

2. CBSE 2025Set ANNUAL1 markMCQ
   Q.Microorganism related to the production of biogas is -

   (a) Virus

   (b) Protozoa

   (c) Bacteria

   (d) Fungus

   ›Reveal solutionSolution

   Biogas is generated by anaerobic methanogenic bacteria acting on cattle dung/organic slurry inside a biogas plant.

   A biogas plant (gobar gas plant) contains a mixed population of anaerobic bacteria, including methanogens such as Methanobacterium, that digest cellulosic and other organic material present in dung slurry and release a mixture of gases (mainly methane, along with CO2, H2, H2S) that is used as fuel. Viruses, protozoa and fungi are not the microbes responsible for this anaerobic methane fermentation.

   ✓Final answer

   (c) Bacteria.

3. CBSE 2025Set ANNUAL1 mark
   Q.Microbes can be used as a source of energy. Comment.

   ›Reveal solutionSolution

   Anaerobic, methane-producing bacteria digest organic waste to yield biogas, a microbially-generated fuel source.

   A group of bacteria called methanogens (e.g. Methanobacterium) live anaerobically in the rumen of cattle and also in anaerobic sludge, where they break down cellulosic/organic material and release a mixture of gases dominated by methane (CH4), along with CO2 and H2 — collectively called biogas or gobar gas. This process is harnessed commercially in biogas plants: cattle dung (and other organic waste) mixed with water (slurry) is fed into a sealed digester (floating-drum or fixed-dome design) where methanogenic bacteria digest it anaerobically. The biogas so produced is piped out and used as a fuel for cooking and lighting, especially in rural India, and the leftover slurry serves as an excellent organic manure/biofertiliser rich in nitrogen and phosphorus. This makes methanogenic microbes a genuine renewable source of energy.

   ✓Final answer

   Yes — microbes (methanogenic bacteria such as Methanobacterium) are used as a source of energy by digesting organic waste (e.g. cattle dung) anaerobically in biogas plants to produce biogas (methane), used as fuel for cooking and lighting.

4. CBSE 2025Set ANNUAL1 markMCQ
   Q.A family residing in a rural area needs a clean and cheap fuel that produces very few pollutants. Which microbes will you suggest for this family ?

   (i) Aerobic bacteria called Methanobacterium

   (ii) Anaerobic bacteria called Methanobacterium

   (iii) Aerobic bacteria called Mycobacterium

   (iv) Anaerobic bacteria called Mycobacterium

   ›Reveal solutionSolution

   Biogas (mainly methane) is generated by anaerobic methanogenic bacteria such as Methanobacterium, which digest organic/cattle waste in the absence of oxygen inside a biogas plant.

   A clean, cheap fuel producing very few pollutants points to biogas. Biogas is produced by a group of bacteria called methanogens (e.g. Methanobacterium), which grow anaerobically (in the absence of oxygen) on cellulosic material and produce a large amount of methane along with CO2 and H2 — this mixture is called biogas. Cattle dung, used commonly in rural India, is rich in these bacteria (also called gobar gas). Biogas plants are typically built in rural/farming settings where these bacteria digest cattle-shed waste (dung, plant material) anaerobically to release biogas that is used as fuel for cooking and lighting — it is renewable, cheap, and burns cleanly with far fewer pollutants than firewood or fossil fuel.

   The options mentioning "aerobic" bacteria are wrong because methanogenesis strictly requires anaerobic (oxygen-free) conditions; Mycobacterium is unrelated to biogas production (it is a genus containing disease-causing species like M. tuberculosis).

   ✓Final answer

   Anaerobic bacteria called Methanobacterium (Option ii) should be suggested to produce clean, cheap biogas fuel.

5. CBSE 2024Set ANNUAL1 mark
   Q.Write the name of bacteria that produces methane.

   ›Reveal solutionSolution

   Methanogenic archaebacteria, e.g. Methanobacterium, live in anaerobic conditions (like the rumen of cattle or biogas plant slurry) and produce methane gas as a metabolic by-product.

   Methanogens are anaerobic microbes present in the rumen of cattle (where they help digest cellulose and are responsible for the methane cattle release) and are also deliberately cultured in biogas plants, where they act on cattle-dung slurry (gobar gas) to produce a mixture of methane, carbon dioxide and hydrogen sulphide - biogas, used as a fuel.

   ✓Final answer

   Methanogens (e.g. Methanobacterium) - methane-producing anaerobic bacteria.

6. CBSE 2022Set HE2201 mark
   Q.Write the answer in one word/sentence: Main constituent of biogas.

   ›Reveal solutionSolution

   Biogas is a mixture of gases produced by anaerobic bacteria, with methane as its principal, combustible component.

   Biogas is produced by the anaerobic (oxygen-free) breakdown of organic matter — commonly cattle-dung slurry ('gobar gas') or other biodegradable waste — by a consortium of anaerobic bacteria, especially methanogens such as Methanobacterium, in a biogas plant/digester. The resulting gas mixture is roughly 50–70% methane, along with carbon dioxide, hydrogen sulphide and other gases, and because of its high methane content it can be burnt directly as a fuel for cooking and lighting.

   ✓Final answer

   Methane (CH₄) is the main constituent of biogas, produced by methanogenic bacteria acting on cattle-dung/organic slurry.

7. CBSE 2022Set ANNUAL1 markMCQ
   Q.Gobar gas contains mainly

   (a) CH₄ and CO₂

   (b) CH₄ and O₂

   (c) CH₄ and H₂

   (d) CH₄ and H₂O

   ›Reveal solutionSolution

   Biogas (gobar gas) is a mixture of mainly methane and carbon dioxide, produced by anaerobic bacteria digesting cattle dung.

   Biogas (gobar gas) is produced through the activity of a consortium of anaerobic bacteria (collectively called methanogens, e.g., Methanobacterium), which digest complex organic matter (cattle dung/cellulosic waste) in the absence of oxygen inside a biogas plant. The gas produced is mainly a mixture of methane (CH₄), along with CO₂, hydrogen sulphide, and other gases in smaller amounts. Methane is combustible, making biogas useful as a source of energy for cooking and lighting in rural areas, while the leftover slurry is a good manure/biofertiliser.

   ✓Final answer

   (a) CH₄ and CO₂

8. CBSE 2021Set D1 markMCQ
   Q.Biogas contains

   (a) CO2

   (b) H2

   (c) CH4

   (d) All of these

   ›Reveal solutionSolution

   Biogas contains CH4, CO2 and H2 — so all of these.

   Biogas is produced by the anaerobic action of methanogenic bacteria (e.g. Methanobacterium) on organic waste such as cattle dung. The gas mixture is predominantly methane (CH4, the main combustible component), together with carbon dioxide (CO2), hydrogen (H2) and small amounts of hydrogen sulphide. Because all three listed gases are present, the correct choice is 'All of these'.

   ✓Final answer

   (D) All of these.

9. CBSE 2021Set ANNUAL1 markMCQ
   Q.Biogas is mainly –

   (i) O2

   (ii) CO2

   (iii) N2

   (iv) CH4

   ›Reveal solutionSolution

   Biogas is produced by anaerobic methanogenic bacteria and is mostly methane.

   Biogas is generated when a consortium of anaerobic bacteria — including cellulolytic bacteria and methanogens such as Methanobacterium — digest organic waste (cattle dung, plant residue) in the absence of oxygen inside a biogas plant. The resulting gas mixture is predominantly methane (CH4), with smaller amounts of CO2, H2S and other gases, making it flammable and useful as a fuel.

   ✓Final answer

   (iv) CH4.

10. CBSE 2020Set ANNUAL1 markMCQ
    Q.Microbe which help in the production of Biogas.

    (a) Aspergillus niger

    (b) Trichoderma Polysporum

    (c) Saccharomyces cerevisiae

    (d) Methanobacterium

    ›Reveal solutionSolution

    Biogas (mainly methane) is produced by methanogenic bacteria such as Methanobacterium acting on organic waste under anaerobic conditions.

    Biogas plants use a mixed population of anaerobic bacteria called methanogens, of which Methanobacterium is a common representative, to break down cellulosic/organic waste (commonly cattle dung, in 'gobar gas' plants) into biogas — chiefly methane, along with CO2 and H2S. The other options have different roles: Aspergillus niger is used to produce citric acid; Trichoderma polysporum is a source of the immunosuppressant cyclosporin-A; Saccharomyces cerevisiae (baker's/brewer's yeast) is used in fermentation for bread, beer and wine, not biogas.

    ✓Final answer

    (d) Methanobacterium — a methanogen used in biogas (gobar gas) production.

11. CBSE 2019Set ANNUAL1 mark
    Q.Define biogas.

    ›Reveal solutionSolution

    Biogas is a methane-rich fuel gas generated by methanogenic bacteria anaerobically digesting organic/cattle-dung waste in a biogas plant.

    Biogas is produced when a mixed population of anaerobic bacteria (including methanogens such as Methanobacterium) breaks down complex organic matter - cattle dung and plant/animal waste slurry - in an oxygen-free (anaerobic) environment inside a biogas/gobar-gas plant. The digestion of cellulosic/organic material produces a gas that is largely methane (CH4, ~50-70%), along with carbon dioxide, hydrogen sulphide and other gases. Because methane burns readily, biogas is used directly as a cooking and lighting fuel, and the leftover slurry serves as a good organic manure rich in nitrogen and phosphorus.

    ✓Final answer

    Biogas = a combustible gas mixture (mainly CH4) produced by anaerobic microbial digestion of organic waste, used as fuel.

12. CBSE 2017Set ANNUAL1 mark
    Q.Why bio gas plants are more available in rural areas than urban areas? Give one point.

    ›Reveal solutionSolution

    Rural areas have the abundant cattle dung and farm waste that biogas plants need as raw material, which is why such plants are far less common in cities.

    Biogas plants require a continuous supply of organic feedstock — chiefly cattle dung (gobar), along with agricultural residues — to be fed into the digester for anaerobic microbial fermentation. Rural households in India commonly keep cattle and have easy access to this raw material as well as the open space required to build and operate a biogas plant. Urban areas, in contrast, have far fewer livestock, limited open space, and no easy supply chain for dung/organic waste, making biogas plants impractical there.

    ✓Final answer

    Because rural areas have ready access to cattle dung and organic waste (the raw material for biogas production) and the open space needed to build a plant, which urban areas generally lack.