A diagram of a biogas plant shows a concrete tank 10–15 feet deep filled with a slurry of cattle dung. A floating cover over the slurry rises as gas is produced, a pipe from the top supplies the gas, and spent slurry leaves through another outlet. Which statement about this plant is correct?
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Methanogens such as Methanobacterium grow anaerobically on cellulosic material and produce methane along with CO2 and H2; they are found in cattle rumen and dung. In the biogas plant, gas collects under the floating cover, and spent slurry is removed and used as fertiliser.
- A.
Azotobacter is a free-living nitrogen fixer; biogas comes from anaerobic methanogens.
- B.
Methanogens are anaerobic, and the spent slurry is used as fertiliser.
- D.
Trichoderma is a biocontrol fungus, not a methane producer.
NCERT: Class 12 Biology, Chapter 8, 8.4