Greenhouse Effect – Natural and Man-made Sources of Methane

Methane is one of the greenhouse gases that contribute to the greenhouse effect. It is the major contributor to our planet. Let us look what are the natural and man-made sources that produce methane gas to our planet.

Greenhouse Effect from Natural sources

Greenhouse Effect (Methane): Wetlands

Wetlands are the major contributor for global methane emissions from natural resources where they are responsible for approximately 170 Tg of methane per year, ranging from 105 to 278 Tg per year.

The methanogenic bacteria live in wetlands and produce methane during the decomposition of organic material.  The bacteria require environments without oxygen to live and abundant of organic matter, to be their good habitat where both conditions are existed in wetland conditions.

Greenhouse Effect (Methane): Termites

Termites are types of insects, which are thought to produce somewhere between 2 and 22 Tg of methane per year as part of their normal digestive process. Since, the populations of these insects vary among different regions of the world thus the emission of methane also are depend on their populations.

Greenhouse Effect (Methane): Oceans, rivers, and estuaries

Oceans, rivers, and estuaries are accounted for approximately 9 Tg of methane per year ranging from 2 to 16 Tg per year. Generally the sources of methane from oceans could not be identified clearly; however there are two identified sources include the anaerobic digestion in marine zooplankton and fish, while another one is from methanogenisis in sediments and drainage areas along coastal regions.

Greenhouse Effect (Methane): Hydrates

Hydrates, aka methane clathrate or methane ice, range from 2 Tg to 9 Tg of global methane emissions per year. These are solid compounds within which methane is trapped in the crystal structures of water ice. The solids can be found in Polar Regions and in ocean floor sediments of the outer continental margin throughout the world. The changes in temperature, pressure, salt concentrations, and other factors release methane from these hydrates.

A conservative estimate based on information from the USGS and other studies projects that global amounts of carbon trapped in gas hydrates is very large than the amount of carbon in all known coal reserves on Earth. Because of this large potential for emissions, there is much ongoing scientific research related to analyzing and predicting how changes in the ocean environment affect the stability of hydrates.

Greenhouse Effect (Methane): Geologic

Geologic methane emissions amount to anywhere between 42 Tg and 64 Tg per year. Geologic emissions are more difficult to measure because there are so many small point sources around the globe. These sources include gryphons, steam vents, bubbling pools, and mud volcanoes.

The mud volcanoes are one of the most dominant geologic methane sources. These structures can be up to 10 kilometers in diameter and usually formed near fossil fuel deposits or on tectonic plate boundaries. They release methane gas along with smaller amounts of carbon dioxide, nitrogen, and helium. There are over 1,000 such structures have been located on land or in shallow water.

Greenhouse Effect (Methane): Wildfires

Wildfires are responsible for an estimated 2 Tg to 5 Tg of methane emissions per year. This number is an estimate and only relevant to natural forest fires and not human-caused deforestation which release a large amount of methane each year as well.

Incomplete combustion of organic material during fires results in the emission of methane. In certain areas, there are other considerations to take into account, such as the release of methane from the burning of permafrost in high latitude regions. The resulting warmer temperature of soil after a fire tends to encourage higher microbial activity. This activity increases the diffusion of methane from the soil to the atmosphere.

Greenhouse Effect (Methane): Wild animals

Wild animals such as bison and buffaloes are known to release methane in estimated quantities of up to 15 Tg per year. These estimates are based on the calculations of species population of wild animals.

Greenhouse Effect from Man-made Sources

Greenhouse Effect (Methane): Landfills

Landfills are the 3rd–largest man–associated source of methane , which is accounting for approximately 17 % of all methane pollutants. Basically, methane is generated inside landfills and open dumps as waste materials decompose under anaerobiotic conditions (without the need of oxygen).

The actual amount of methane created is determined by the quantity and humidity content of the waste and the management practices at the site.

Greenhouse Effect (Methane): Natural gas and petroleum systems.

Methane is a main element of natural gas. Methane losses occur during the production, processing, storage, transmission, and distribution of natural gas. Given that gas is frequently found in conjunction with oil, the production, refinement, transportation, and storage of crude oil is also an origin of methane emissions.

Greenhouse Effect (Methane): Coal mining

Methane caught in coal deposits and in the surrounding strata is released through typical mining operations both in underground and surface mines. Furthermore, handling of the coal right after mining results in methane emissions.

Greenhouse Effect (Methane): Livestock intestinal fermentation.

Among domesticated livestock, ruminant animals (cattle, buffalo, sheep, goats, and camels) produce a substantial amount of methane as part of their normal digestive processes. Inside the rumen, or large fore-stomach, of these animals, microbial fermentation turns feed into products that can be digested and used by the animal.

This microbial fermentation process, known as enteric fermentation, produces methane as a by-product, which can be exhaled by the animal. Methane is also produced in smaller quantities by the digestive processes of other animals, including humans, but emissions from these sources are insignificant.

Greenhouse Effect (Methane): Livestock manure management.

Methane is produced during the anaerobic (i.e., without the need of oxygen) decomposition of organic material in livestock manure management systems. Liquid manure management systems, for example lagoons and holding tanks, can trigger significant methane generation and these systems are commonly used at larger swine and dairy operations. Manure deposited on fields and pastures, or otherwise handled in a dry form, creates insignificant amounts of methane.

Greenhouse Effect (Methane): Wastewater treatment facility

Wastewater from domestic (municipal sewage) and industrial sources is treated to remove soluble organic matter, suspended solids, pathogenic organisms, and chemical contaminants.

These treatment processes can create methane emissions if organic constituents in the wastewater are treated anaerobically (i.e., without oxygen) and if the methane produced is released to the atmosphere. In addition, the sludge made out of some treatment processes may be additional biodegraded under anaerobic conditions, resulting in methane emissions.

These emissions can be avoided, however, by treating the wastewater and the associated sludge under aerobic conditions or by capturing methane released under anaerobic conditions.

Greenhouse Effect (Methane): Rice cultivation.

Methane is actually generated throughout flooded rice cultivation from the anaerobic (without oxygen) decomposition of organic matter inside the soil. Flooded soils are ideal conditions for methane production because of their high concentrations of organic substrates, oxygen-depleted conditions, and moisture.

The level of emissions may differ with soil conditions and generation practices as well as local climate. A number of farming practices have shown guarantee for reducing methane emissions from rice cultivation.

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