What gases are produced in anaerobic sludges digesters ?

Explanation

Sludge is the remaining part of organic matter after secondary treatment of sewage. In sludge digesters, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi present in the sludge. During this process, bacteria produce a mixture of gases, such as methane, hydrogen sulphide and carbon dioxide which form biogas. It can be used as a source of energy.