Anaerobic Decomposition of Organic Matter

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Organic Matter Decomposition Degradation of Plant Residues Humus Genera of Microorganisms Capable of Utilising Different Components of Organic Matter Humic Acids Beneficial Role of Humic Acids

Anaerobic Decomposition of Organic Matter

Anaerobic Decomposition of Organic Matter
Under anaerobic conditions, decomposition of organic residues takes place by the activity of both mesophrk and thermophilic microorganisms resulting in the production of carbondioxide, hydrogen, ethyl alcohol and organic acids such as acetic, formic, lactic, succinic and butyric acids. Among the mesophilic flora, bacteria are more active than fungi or actinomycetes in cellulolytic activity. They belong to the genus Clostridium and are numerous in peaty soils and manure pits but rarely encountered in cultivated arable soils. In compost heaps, both mesophilic and thermophilic microorganisms (bacteria and actinomycetes) are important in the break down of cellulose substrates.

As stated above, the primary microbial colonizers initially break down the complex carbohydrates and proteins into organic acids and alcohols. At a later stage, the methane bacteria which are strict anaerobes begin to act upon the secondary substrates chiefly lactic, acetic and butyric acids and ferment them into CH₂ and CO₂ whose ratio is variable depending on the nature of reactions. It is not easy to isolate pure cultures of methane bacteria. However, by enrichment culture technique, methane bacteria have been isolated and grouped under four genera: Methanobacterium, Methanobacillus, Methanosarcina and Methanococcus.

Experiments with pure cultures as well as mixed cultures of methane bacteria have shown that among the several types of reactions which can produce CH₄, the following typical ones are important:

Anaerobic Decomposition of Organic Matter

Anaerobic Decomposition of Organic Matter

I	Non-methanogens	II	Methanogens
A.	Clostridium acetobutylicum	C1	H2 oxidizing methanogens
	Eubacterium limosum		Methanobacterium
			Methanobrevibacter
			Methanospirillum
B.	Volatile fatty acid oxidizers	C2	Aceticlastic methanogens
	Syntrophomonas wolfeii		Methanosoricina
	Syntrophobacter wolinii

(1) CO₂ + 4H₂ CH₄ + 2H₂O
(2) 4HCOOC CH₄ + 3CO₂ + 2H₂O
(3) CH₃COOH CH₄ + CO₂
(4) 2CH₃CH₂H 3CH₄ + CO₂

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Mineralization and Immobilization Process Effects of Residues of Crops on Plant Growth Soil Sickness Composting Vermicomposting Green Manure Anaerobic Decomposition of Organic Matter Biogas Degradation of Hydrocarbons

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