Q4. Where are methanogens commonly found?
In the anaerobic sludge of sewage treatment and in the rumen of cattle, and so in cattle dung (NCERT page 155).
Q5. Which gases do methanogens produce while growing anaerobically on cellulosic material?
Large amounts of methane, along with CO2 and H2 (NCERT page 155). The reading note on the main page explains what the methanogens themselves do (beyond the NCERT text).
Q6. How deep is the concrete tank of a typical biogas plant, and what is fed into it?
About 10–15 feet deep; bio-wastes are collected in it and a slurry of dung is fed (NCERT page 155).
Q7. Why are biogas plants more often built in rural areas?
Cattle dung is available in large quantities there, because cattle are used for a variety of purposes (NCERT page 156).
Q8. To which group of monerans does NCERT Class 11 assign the methanogens?
The archaebacteria (NCERT Class 11 Biology, Section 2.1.1, page 13).