Decomposition is primarily carried out by microorganisms like bacteria and fungi, and their activity is influenced by the presence or absence of oxygen. This leads to two main types of decomposition processes: aerobic decomposition (with oxygen) and anaerobic decomposition (without oxygen).

In aerobic conditions, oxygen is present, and the decomposition process is carried out by aerobic microorganisms. These organisms require oxygen to break down organic matter efficiently. Oxygen serves as the final electron acceptor in their metabolic processes, allowing them to completely oxidize organic compounds. Aerobic decomposition process is quick and complete break down of organic matter takes place here.

In anaerobic conditions, the environment lacks oxygen, and decomposition is carried out by anaerobic microorganisms. These organisms are adapted to function in low or zero-oxygen environments and use alternative electron acceptors in their metabolic processes. This process is slower than aerobic decomposition. Here incomplete/partial decomposition takes place which produces foul smell.

As the microorganisms decompose the organic matter, they release various byproducts, including organic acids. These organic acids are formed as a result of the breakdown of complex organic compounds into simpler molecules. Common organic acids produced in this process include acetic acid, citric acid, and humic acids.

Dr Chandan De thank you for your contribution to the discussion

In the oxygen cycle, oxygen is utilized for the breakdown of organic waste. The organic wastes obtained from living organisms are biodegradable because some aerobic bacteria convert organic waste materials into inorganic materials in the presence of oxygen by releasing carbon dioxide and water. Oxygen is needed for many decomposers to respire, to enable them to grow and multiply. This is why we often seal food in bags or cling film before putting it in the fridge. As the volume of available oxygen increases, the rate of decomposition also increases. Some decomposers can survive without oxygen. Oxygen availability is thus required and changes in its accessibility lead to drastic metabolic rearrangements. Ultimately, aerobic organisms die if the absence of oxygen is prolonged. A lower level of oxygen can result from environmental conditions, but also anatomical and tissue constraints. Aerobic decomposition takes place in the presence of oxygen. This is most common to occur in nature. Living organisms that use oxygen to survive feed on the body. Anaerobic decomposition takes place in the absence of oxygen. Dissolved oxygen levels drop in a water body that contains a lot of dead, decomposing material. Elevation- the amount of oxygen in elevation increases. Since streams get much of their oxygen from the atmosphere, streams at higher elevations will generally have less oxygen. In most cases, these bacteria require oxygen to grow because their methods of energy production and respiration depend on the transfer of electrons to oxygen, which is the final electron acceptor in the electron transport reaction. Biological oxygen demand (BOD) is a measure of the amount of oxygen required aerobically to decompose organic matter in the water. BOD is the amount of dissolved oxygen required by microorganisms to breakdown organic matter present in water. Oxygen helps break down organic matter to release carbon dioxide a process you can see in a backyard compost pile. Yet in some places on Earth, organic matter such as plant debris can persist for thousands of years despite the presence of abundant oxygen. A combustion reaction is an exothermic reaction in which something reacts with oxygen. The combustion of organic compounds usually takes the form organic compound + oxygen => water + carbon dioxide. During the first phase of decomposition, aerobic bacteria—bacteria that live only in the presence of oxygen—consume oxygen while breaking down the long molecular chains of complex carbohydrates, proteins, and lipids that comprise organic waste. The primary byproduct of this process is carbon dioxide. Decaying organic matter produces H+ which is responsible for acidity. The carbon dioxide (CO2) produced by decaying organic matter reacts with water in the soil to form a weak acid called carbonic acid. This is the same acid that develops when CO2 in the atmosphere reacts with rain to form acid rain naturally. In general, pH values in the topsoil are lower because topsoil is rich in organic matter and the decomposition of organic matter will lead to the production of more organic acids, thus lowering pH of topsoil. Volatile fatty acids exist in the flooded soil during the course of the decomposition of organic materials. Sodium salts of formic, acetic, propionic, butyric, lactic and succinic acids, which are formed by the anaerobic fermentation. Organic matter is usually considered to lower soil pH by releasing hydrogen ions that were associated with organic anions or by nitrification in an open system. Under aerobic soil conditions decarboxylation is a major process in organic matter decomposition. The decomposition of carbohydrates in the glycolytic pathway produces carboxylic groups which, after dissociation, may decrease soil pH.