Methane methanogenesis

Methane emissions from any ecosystem, particularly a rice agroecosystem (Figure 1), are governed by the magnitude and balance of microbial CH4 production (methanogenesis) and oxidation (methanotrophy), which occur by separate microbial communities. The two groups... 

Dissolved arsenic is correlated with ammonia (Fig. 4), consistent with a release mechanism associated with the oxidation of organic carbon. Other chemical data not shown here provide clear evidence of iron, manganese and sulfate reduction and abundant methane in some samples indicates that methanogenesis is also occurring. It is not clear however if arsenic is released primarily by a desorption process associated with reduction of sorbed arsenic or by release after the reductive dissolution of the iron oxide sorbent. Phreeqc analysis shows PC02 between 10"12 and 10"° bars and that high arsenic waters are supersaturated with both siderite and vivianite. 

The anaerobic decomposition of organic matter by fermentation, methanogenesis (methane formation) and sulfate respiration is exemplified in Table 3.2. 

Methanogenesis a process that transforms the fermentation products (VFAs) into methane. 

Fermentation of the wastes - conversion to acetates Acetogenesis - conversion to acids, formaldehyde and Hydrogen, and Methanogenesis - conversion of formaldehyde, acetates, and acids to CO2 and Methane... 

Methanogenesis. Finally, the products of either acidogenesis or acetogenesis are transformed into methane and carbon dioxide by the methanogenic bacteria. It is well known that this step is the limiting one in case of nonparticulate substrate or non-excessively complex organic matter. 

The standard free energy change for methanogenesis from hydrogen and CO2 is more exergonic than that of acetogenesis (AG o = -135.6kJ per mole methane and AG o = -104.6kJ per mole acetate, respectively). However, certain conditions compromise or inhibit methanogenesis (Fig. 13.5). In a complex ecosystem, the metabolic interactions of the anaerobic populations... 

Methanogenesis The anaerobic microbial process that produces methane. 

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