Methanogens do not produce:

Nitrogen and Oxygen

The correct answer is Option (4) - Nitrogen and Oxygen

Biogas is a gas mixture primarily composed of methane, produced through microbial activity. Certain bacteria that thrive in anaerobic conditions and feed on cellulosic materials are responsible for generating significant quantities of methane, along with carbon dioxide (CO₂) and hydrogen (H₂). These specialized bacteria fall under the collective term "methanogens," and one well-known example is Methanobacterium. Methanogens are commonly found in anaerobic sludge used during sewage treatment processes. They are also naturally present in the rumen, a section of the stomach, of cattle.

Cattle consume a diet rich in cellulosic materials, which are also found in the rumen. Within the rumen, methanogens play a crucial role in breaking down cellulose and contributing to the nutritional needs of cattle. Consequently, the dung or excreta of cattle, often referred to as "gobar," is abundant in these methane-producing bacteria. Gobar, or cattle dung, can be effectively utilized for the generation of biogas, commonly referred to as "gobar gas." This process harnesses the methane-producing capabilities of methanogens to provide a renewable and sustainable source of energy.