Methane emissions derive from both natural and human sources. The main natural sources, which account for 36% of methane emissions, include wetlands, termites and the oceans. Anthropogenic activities make up the majority of methane emissions at 64% that mainly comes from landfills, livestock farming, as well as the production, transportation and use of fossil fuels.
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NATURAL ACTIVITIES of METHANE EMISSIONS
WETLANDS
Wetlands are the largest natural source of methane that produce 78% of methane emissions. The water-logged conditions of wetlands are perfect for microbes who require environments with no oxygen and abundant organic matter. While part of wetland related emissions is absorbed by methane-consuming microbes, a large percentage escapes into the atmosphere. Wetlands create 147 million tonnes of methane each year.
Wetlands are the largest natural source of methane that produce 78% of methane emissions. The water-logged conditions of wetlands are perfect for microbes who require environments with no oxygen and abundant organic matter. While part of wetland related emissions is absorbed by methane-consuming microbes, a large percentage escapes into the atmosphere. Wetlands create 147 million tonnes of methane each year.
TERMITES
Termites are a significant natural source of methane. During the normal digestion process of a termite, methane is produced. Termites eat cellulose but rely on micro-organisms in their gut to digest it which produces methane during the process. This is responsible for 12% of natural methane emissions. Each termite produces very small amounts of methane on a daily basis. However, when this is multiplied by the world population of termites, their emissions add up to 23 million tonnes of methane annually.
Termites are a significant natural source of methane. During the normal digestion process of a termite, methane is produced. Termites eat cellulose but rely on micro-organisms in their gut to digest it which produces methane during the process. This is responsible for 12% of natural methane emissions. Each termite produces very small amounts of methane on a daily basis. However, when this is multiplied by the world population of termites, their emissions add up to 23 million tonnes of methane annually.
HUMAN ACTIVITIES of METHANE EMISSIONS
FOSSIL FUELS
Methane emissions are produced wherever there are fossil fuels. It is released whenever fossil fuels are extracted from the earth whether it is natural gas (which is mostly methane), coal or petroleum. During the geological process of coal formation, pockets of methane get trapped around and within the rock. Coal mining related activities (extraction, crushing, distribution, etc.) release some of this trapped methane. Methane is emitted from active underground and surface mines as well as abandoned ones. There are additional methane emission that are created during any type of handling, transportation (pipeline, truck delivery, etc.) or refinement of fossil fuels. Many times there is leakage throughout the different levels of industrial release. Because gas is often found in conjunction with oil, the production, refinement, transportation, and storage of crude oil is also a source of methane emissions. Finally some methane is also produced during fossil fuel combustion. Incomplete combustion of fossil fuels also produces methane emissions. No combustion process is one hundred percent efficient, so when fossil fuels are used to create electricity, heat or power vehicles these all contribute as sources. Henceforth, the largest human source of methane emissions is from the production, processing, storage, transmission, distribution and combustion of fossil fuels. This is responsible for around 29-33% of human methane emissions. Fossil fuel production, distribution and use creates 110 million tonnes of methane annually. |
LIVESTOCK FARMING
An important source of methane emissions is from enteric fermentation in farm animals. This is responsible for 26% of human methane emissions. Animals like cows, sheep and goats are examples of ruminant animals and during their normal digestion process they create large amounts of methane. Enteric fermentation occurs because of microorganisms in the stomach of these animals, which creates methane as a by-product that is either exhaled by the animal or released via flatus. Because humans raise these animals for food, their emissions are considered human-related. The meat that we eat everyday contributes significantly to total methane emissions because of this. Livestock farming creates 90 million tonnes of methane annually. Livestock related emissions have grown mainly because of the large growth of livestock populations worldwide over the last fifty years. Global livestock production has increased substantially since the 1960s with beef production more than doubling during this time.
An important source of methane emissions is from enteric fermentation in farm animals. This is responsible for 26% of human methane emissions. Animals like cows, sheep and goats are examples of ruminant animals and during their normal digestion process they create large amounts of methane. Enteric fermentation occurs because of microorganisms in the stomach of these animals, which creates methane as a by-product that is either exhaled by the animal or released via flatus. Because humans raise these animals for food, their emissions are considered human-related. The meat that we eat everyday contributes significantly to total methane emissions because of this. Livestock farming creates 90 million tonnes of methane annually. Livestock related emissions have grown mainly because of the large growth of livestock populations worldwide over the last fifty years. Global livestock production has increased substantially since the 1960s with beef production more than doubling during this time.
LIVESTOCK MANURE MANAGEMENT
Methane is produced during the anaerobic decomposition of organic material in livestock manure management systems. Liquid manure management systems, such as lagoons and holding tanks, can cause significant methane production 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, produces insignificant amounts of methane. Manure management is responsible for 10% of human methane emissions.
Methane is produced during the anaerobic decomposition of organic material in livestock manure management systems. Liquid manure management systems, such as lagoons and holding tanks, can cause significant methane production 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, produces insignificant amounts of methane. Manure management is responsible for 10% of human methane emissions.
LANDFILLS
Another important human source of methane emissions is from landfills.. Methane is generated by the decomposition of biodegradable solid waste in landfills as well as animal and human waste streams. Landfills and open garbage dumps are full of organic matter from our garbage (things like food scraps, newspapers, cut grass and leaves). Every time new garbage comes in it is pilled over the old garbage that was already there. The organic matter in our garbage gets trapped in anaerobic conditions where there is no oxygen. This provides excellent conditions for methane producing microbes to break down the waste, which produces large amounts of methane emissions. Even after a landfill is closed, the bacteria will continue to decompose the buried waste and emit methane for years. Landfills accounts for 16-18% of human methane emissions. Landfills and waste produces 55 million tonnes of methane annually.
Another important human source of methane emissions is from landfills.. Methane is generated by the decomposition of biodegradable solid waste in landfills as well as animal and human waste streams. Landfills and open garbage dumps are full of organic matter from our garbage (things like food scraps, newspapers, cut grass and leaves). Every time new garbage comes in it is pilled over the old garbage that was already there. The organic matter in our garbage gets trapped in anaerobic conditions where there is no oxygen. This provides excellent conditions for methane producing microbes to break down the waste, which produces large amounts of methane emissions. Even after a landfill is closed, the bacteria will continue to decompose the buried waste and emit methane for years. Landfills accounts for 16-18% of human methane emissions. Landfills and waste produces 55 million tonnes of methane annually.
WASTEWATER
Wastewater from domestic, municipal and industrial sources can also produce methane emissions. Wastewater can be either released, stored or sent for treatment to remove contaminants. 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 produce methane emissions if organic constituents in the wastewater are treated anaerobically and if the methane produced is released to the atmosphere. In addition, the sludge produced from some treatment processes may be further biodegraded under anaerobic conditions, resulting in methane emissions.
Wastewater from domestic, municipal and industrial sources can also produce methane emissions. Wastewater can be either released, stored or sent for treatment to remove contaminants. 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 produce methane emissions if organic constituents in the wastewater are treated anaerobically and if the methane produced is released to the atmosphere. In addition, the sludge produced from some treatment processes may be further biodegraded under anaerobic conditions, resulting in methane emissions.
BIOMASS BURNING
Biomass burning causes a substantial amount of methane emissions. Biomass is material from living or dead organic matter. Incomplete burning of biomass creates methane emissions and huge amounts can be produced during large scale burning. This is responsible for 11% of human methane emissions. Large open fires are mainly used by humans to destroy crop waste and clear land for agricultural or other uses. While natural wildfires can contribute to this, the great majority of biomass burning is caused by human beings. Biomass burning creates 38 million tonnes of methane annually.
Biomass burning causes a substantial amount of methane emissions. Biomass is material from living or dead organic matter. Incomplete burning of biomass creates methane emissions and huge amounts can be produced during large scale burning. This is responsible for 11% of human methane emissions. Large open fires are mainly used by humans to destroy crop waste and clear land for agricultural or other uses. While natural wildfires can contribute to this, the great majority of biomass burning is caused by human beings. Biomass burning creates 38 million tonnes of methane annually.
RICE AGRICULTURE
Another substantial human source of methane emissions is from rice agriculture. Paddy fields for rice production are essentially man-made wetlands. They are characterized by high moisture content, oxygen depletion and ample organic material. This creates a great environment for methane producing microbes that decompose the organic matter. Though some of the methane produced is absorbed by methane-consuming microorganisms, the vast majority is released into the atmosphere. Due to the swamp-like environment of rice fields, this crop is responsible for 9% of human methane emissions. Rice agriculture creates 31 million tonnes of methane annually.
Another substantial human source of methane emissions is from rice agriculture. Paddy fields for rice production are essentially man-made wetlands. They are characterized by high moisture content, oxygen depletion and ample organic material. This creates a great environment for methane producing microbes that decompose the organic matter. Though some of the methane produced is absorbed by methane-consuming microorganisms, the vast majority is released into the atmosphere. Due to the swamp-like environment of rice fields, this crop is responsible for 9% of human methane emissions. Rice agriculture creates 31 million tonnes of methane annually.
BIOFUELS
Annually 12 million tonnes of methane are produced by biofuels making it a significant source. Biomass that is used to produce energy for domestic, industrial or transportation purposes are called biofuels. Incomplete biofuel combustion leads to the production of methane. An estimated 80% of biofuels are used for domestic cooking, heating, and lighting mostly in open cooking fires burning wood, agricultural waste, or animal dung. This is the single largest contributor to global biofuel emissions. Almost half of the world's population, about 2.7 billion people, use solid biofuels to cook and heat their homes on a daily basis. Most are poor, and live in developing countries. 18% of biofuels are used by low-technology, largely unregulated, micro-enterprises such as brick or tile making kilns, restaurants, etc. The balance of the biofuels are consumed for transportation uses. Biofuels are responsible for 4% of human methane emissions.
Annually 12 million tonnes of methane are produced by biofuels making it a significant source. Biomass that is used to produce energy for domestic, industrial or transportation purposes are called biofuels. Incomplete biofuel combustion leads to the production of methane. An estimated 80% of biofuels are used for domestic cooking, heating, and lighting mostly in open cooking fires burning wood, agricultural waste, or animal dung. This is the single largest contributor to global biofuel emissions. Almost half of the world's population, about 2.7 billion people, use solid biofuels to cook and heat their homes on a daily basis. Most are poor, and live in developing countries. 18% of biofuels are used by low-technology, largely unregulated, micro-enterprises such as brick or tile making kilns, restaurants, etc. The balance of the biofuels are consumed for transportation uses. Biofuels are responsible for 4% of human methane emissions.