How many of the following statements are incorrect?

I. The gobar gas is generated from the dung of cattle.
II. A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity.
III. A typical biogas plant has two main outlets, one for biogas which is used by nearby houses and the other for spent slurry which may be used as fertiliser.
IV.Biogas plants are more often built in urban areas due to the availability of large quantities of cattle dung and thus the biogas produced is used for cooking and lighting.

During this digestion in anaerobic sludge digester, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as a source of energy as it is inflammable.

A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity.

The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. The
spent slurry is removed through another outlet and may be used as fertiliser.

Cattle dung is available in large quantities in rural areas where cattle are used for a variety of purposes. So biogas plants are more often built in rural areas.