How deep is the concrete tank built in a biogas plant?

Select the correct sequence of anaerobic digestion during biogas production.

Select the correct option for $Methanogens$.

Consider the following statements about methanogenic bacteria:
$I.$ Methanogenic bacteria are commonly found in the anaerobic sludge formed during sewage treatment.
$II.$ These bacteria also occur in the rumen of cattle,where they act upon cellulosic material to break down cellulose.
$III.$ They play a very important role in the nutrition of cattle by digesting cellulosic material.
Which of the statements given above are correct?

Which bacteria are used in a biogas plant?

How is biogas beneficial compared to conventional energy sources?