It has been shown that generation of methane under various mixed cultures in the presence of coal as substrate involves degradation of coal. There seems to be no single bacteria that can degrade coal from clusters of benzene rings to two to three carbon aliphatic chains that are then converted to methane by methanogenesis. Incubation period of mixed cultures from various sources such as cow dung, paddy held mud, white rot fungus, termite and wood eating insect have generally observed to be nearly 50 days but in many cases longer period up to 70 days or beyond have been observed. Yield of methane was observed to be optimum while using paddy field soil.