Methanogens are strictly anaerobic archaea

which not only take part in the methanogenesis procedure but also limit this process. Temperature plays a key role in the anaerobic fermentation. Temperature could not only directly alter the community structure and function of methanogenic archaea

but also affect the supply of substrates for methanogens

which in turn indirectly regulates the pathways of methanogenic archaea．There are three pathway for methanogenesis

and they are started from acetic acid

H2/CO2 and C-1 compound respetively. Acetoclastic methanogenesis accounts for about two-thirds of the total methane production globally

while hydrogenotrophic methanogenesis accounts for about one third. Methanol- and methyl amine-derived methanogensis is restricted in ocean and saline water. Acetoclastic methanogenesis is the predominant methanogenesis at a low temperature

and methane is produced by acetoclastic and hydrogenotrophic methanogenesis at a medium temperature

while methane is exclusively produced by hydrogenotrophic methanogenesis at a high or ultra-high temperature.