Anaerobic decomposition of organic matter

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

In settings that do not contain oxygen or alternative electron acceptors, methane production is favored. Methane production is the final step in anaerobic decomposition of organic matter. 

Kristensen, E., Ahmed, S.I., and Devol, A.H. (1995) Aerobic and anaerobic decomposition of organic matter in marine sediment Which is fastest Limnol. Oceanogr. 40, 1430-1437. 

It has been inferred from carbon and sulfur dating that the concentration of oxygen in the Earth s atmosphere was less than I part per million volume (ppmv) prior to around 2.4 billion (Ga) years ago, whereas methane would have been present at levels of around 10 to 10 ppmv (compared with its present value of around 1.7 ppmv). Methane is generated in signihcant amounts by the anaerobic decomposition of organic matter in modem marine sediments, but is oxidised by sulfate under the ocean sea floor and never reaches the atmosphere. Prior to the watershed constituted by the appearance of oxygenic photosynthesis, the ocean had little sulfate to support anaerobic oxidation of methane, but as atmospheric oxygen and seawater sulfate levels rose, the consequent anaerobic oxidation of methane would have steadily reduced the net release of methane. 

Aller, R. C., and Yingst, J. Y. (1980). Relationships between microbial distributions and the anaerobic decomposition of organic matter in surface sediments of Long Island Sound,... 

Anaerobic decomposition of organic matter in natural waters Dissolved organic matter will decompose in water under anaerobic (oxygen-free) conditions if appropriate bacteria are present. Anaerobic conditions occur naturally in stagnant water such as swamps and at the bottom of deep lakes. The bacteria operate on carbon so as to disproportionate it. In other words, some carbon is oxidized to carbon dioxide and the rest is reduced to methane (reaction (8))... 

Natural waters may be contaminated with carbon disulphide and hydrogen sulphide from wastewaters from the chemical industry and more frequently by hydrogen sulphide formed during the anaerobic decomposition of organic matter. 

Anaerobic decomposition of organic matter and detritus can result in production of organic acids, which can result in solubilization of phosphorus bound to iron, aluminum, calcium, and magnesium. 

Formation of hydrogen sulphide is observed in the process of anaerobic decomposition of organic matter by sulphate-reducing bacteria. 

Biomethane can be obtained from anaerobic decomposition of organic matter, and the most important sources are digestors (manure and agro-forest matter) and landfills (municipal solid waste). 

Putrefaction Biological decomposition of organic matter with the production of ill-smelling products associated with anaerobic conditions. 

It is less conunonly known that methane was one of the original atmospheric gases and is a normal product of the microbial decomposition of organic matter under anaerobic conditions. Bacteria involved in production of methane are unique in their metabolism and other properties. The balanced... 

Any of the above-mentioned compounds can be found and even synthesized in soil. The simplest example, methane (CH4), is commonly found in the soil atmosphere, ft is produced during the decomposition of organic matter under anaerobic conditions, which can occur even in aerobic soils. It is interesting to note that methane can not only can be produced in aerobic soils but can also be oxidized by soil bacteria in the same soil. 

In broad terms the decomposition of organic matter under anaerobic conditions is expected to be slower than nnder aerobic conditions becanse the free energy changes for the reactions involved are mnch smaller (Table 4.1 and Fignre 4.3). For example, for the aerobic decomposition of CH2O ,... 

Attack by organisms other than SRB. Ammonia and amines are produced by microbial decomposition of organic matter under both aerobic and anaerobic conditions (ammo-nification). (Stott)5 These compounds are oxidized to nitrite by aerobic bacteria such as Nitrosomonas or Nitrobacter species. Nitrobacter is very efficient at destroying the corrosion-inhibition properties, of nitrate-based corrosion inhibitors by oxidation, unless a biocidal agent is included in the formulation. The release of ammonia at the surfaces of heat-exchanger tubes has a detrimental effect. (Stott)5... 

Methane, the simplest of all organic compounds, contains one carbon atom. Methane—the main component of natural gas—occurs widely in nature. Like other hydrocarbons—organic compounds that contain only carbon and hydrogen— methane is combustible that is, it burns in the presence of oxygen. Methane is the product of the anaerobic (without air) decomposition of organic matter by bacteria. The natural gas we use today was formed by the decomposition of organic material millions of years ago. Hydrocarbons. such as methane are discussed in Chapter 4. 

Biogenic activity. In sandy soils, rapid microbial decomposition of organic matter is facilitated up to its mineralization. In clay soils, anaerobic processes are prevalent with humic substances occurring as decomposition products, and under extremely anaerobic conditions, insufficiently decomposed organic matter may be accumulated. 

Bikbulatova, E.M., Skopintsev, B.A. and Bikbulatov, E.S., 1977. Decomposition of organic matter of blue-green algae under aerobic and anaerobic conditions at room temperature ( 20°C). Vodn. Resur., No. 6 132—147 (in Russian). 

The 5 C values of such neoformations appear to be rather elevated. This anomaly of positive values may be explained by the leaching of primary micritic rocks by COj derived from the decomposition of organic matter under anaerobic conditions by bacterial action. This process, as has been described above, leads to CO, which inherits the C-enriched carbon of the functional groups. 

Carbon dioxide and methane are two gaseous end products of decomposition of organic matter under anaerobic conditions, whereas only carbon dioxide is produced under aerobic conditions. Carbon dioxide readily dissolves in water and is partitioned into H2CO3, HCO , and CO as follows ... 

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