Which of the following statements are correct for biogas?

(i) Biogas is a mixture of gases containing predominantly methane produced by the microbial activity and which may be used as fuel.

(ii) Certain bacteria, which grow aerobically on cellulosic material, produce large amount of methane along with CO 2 and H 2 .

(iii) Bacteria involved in production of biogas are collectively called methanogens, and one such common bacterium is Methanobacterium.

(iv) Methanogens are commonly found in the aerobic sludge during sewage treatment.

(v) Methanogens bacteria are also present in the rumen of cattle.

(vi) Gobar (dung) of cattle rich in methanogenic bacteria can be used for generation of biogas, commonly called gobar gas.

(vii) The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).