Methane (CH4) is a hydrocarbon that is a primary component of natural gas. Methane is also a greenhouse gas (GHG), so its presence in the atmosphere affects Earth's temperature and climate system. Methane is emitted from a variety of anthropogenic (human-influenced) and natural sources. Anthropogenic emission sources include landfills, oil and natural gas systems, agricultural activities, coal mining, stationary and mobile combustion, wastewater treatment and certain industrial processes.
Methane is the second most abundant anthropogenic GHG (greenhouse gas) after carbon dioxide (CO2), accounting for about 20% of global emissions. Methane is 25 times more potent than carbon dioxide in trapping heat in the atmosphere. In the last two centuries, their concentrations in the atmosphere have doubled, largely due to human-related activities. As methane is a powerful and short-lived greenhouse gas compared to carbon dioxide, achieving significant reductions would have a rapid and significant effect on atmospheric warming potential.
Who are the biggest methane emitters?
China, the United States, Russia, India, Brazil, Indonesia, Nigeria and Mexico are estimated to be responsible for almost half of all anthropogenic methane emissions. The main sources of methane emissions from these countries vary widely. For example, a major source of methane emissions in China is coal production, while Russia emits most of its methane from natural gas and oil systems. The biggest sources of methane emissions from human activities in the United States are oil and gas systems, enteric fermentation of livestock, and landfills.
Why aren't efforts to capture and profitably use methane emissions more widespread?
Despite the multiple benefits, methane recovery is not widespread for several reasons.
1 - Methane is generally a secondary by-product in the industrial processes from which it is emitted. Coal mines, for example, seek to release methane from the workings of the mine because it can cause explosions. Historically, miners have not viewed associated methane as an energy resource in its own right.
2 - Emissions officers may not be familiar with available technologies for methane recovery or the potential for profitable recovery projects. This is especially true in developing countries, where better access to information and technical training would be beneficial in generating support for methane recovery projects.
3 - Malfunctioning energy markets and financially insolvent utilities and municipalities in many countries fail to provide the private sector with a climate that will attract their investment in projects to capture and utilize methane.
Carbon Dioxide Emissions
Carbon dioxide (CO2) is the main greenhouse gas emitted by human activities. In 2020, CO2 was responsible for about 79% of all US greenhouse gas emissions from human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth's carbon cycle (the natural circulation of carbon between the atmosphere, oceans, soil, plants and animals). Human activities are altering the carbon cycle – both adding more CO2 to the atmosphere and influencing the ability of natural sinks such as forests and soils to remove and store CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.
The main human activity that emits CO2 is the burning of fossil fuels (coal, natural gas and oil) for energy and transport. Certain industrial processes and land use changes also emit CO2. The main sources of CO2 emissions are described below.
• Transport. Combustion of fossil fuels such as gasoline and diesel to transport people and goods was the biggest source of CO2 emissions in 2020, accounting for about 33% of total CO2 emissions and 26% of total greenhouse gas emissions. stove. This category includes domestic transport sources such as road and passenger vehicles, air travel, maritime and rail transport.
• Electricity. Electricity is a significant source of energy and is used to power homes, businesses and industries. In 2020, the combustion of fossil fuels to generate electricity was the second largest source of CO2 emissions, accounting for about 31% of total CO2 emissions and 24% of total greenhouse gas emissions. The types of fossil fuel used to generate electricity emit different amounts of CO2. To produce a given amount of electricity, burning coal will produce more CO2 than natural gas or oil.
• Industry. Many industrial processes emit CO2 through the consumption of fossil fuels. Several processes also produce CO2 emissions through chemical reactions that do not involve combustion, examples include the production of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals. The fossil fuel combustion component of several industrial processes accounted for about 16% of total CO2 emissions and 13% of total greenhouse gas emissions in 2020. Many industrial processes also use electricity and therefore result in indirectly in CO2 emissions from electricity generation.
Carbon dioxide is constantly being exchanged between the atmosphere, ocean and land surface as it is produced and absorbed by many microorganisms, plants and animals. The emissions and removal of CO2 by these natural processes, however, tend to balance out in the absence of anthropogenic impacts. Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change, adding CO2 and other heat-trapping gases to the atmosphere.
Reduction of carbon dioxide emissions
The most effective way to reduce CO2 emissions is to reduce the consumption of fossil fuels. Many strategies to reduce CO2 emissions from energy are transversal and apply to homes, businesses, industry and transport.
Examples of carbon dioxide reduction opportunities
Energy efficiency
Improving the insulation of buildings, traveling in more fuel-efficient vehicles and using more efficient electrical appliances are all ways to reduce energy use and therefore CO2 emissions.
Energy conservation
Reducing personal energy use by turning off lights and electronics when not in use reduces demand for electricity. Reducing the distance traveled in vehicles reduces oil consumption. Both are ways to reduce CO2 emissions from energy through conservation.
Fuel exchange
Producing more energy from renewable sources and using lower carbon fuels are ways to reduce carbon emissions.
Carbon Capture and Sequestration (CCS)
Carbon dioxide capture and sequestration is a set of technologies that can potentially significantly reduce CO2 emissions from new and existing coal and gas power plants, industrial processes and other stationary sources of CO2. For example, a CCS project might capture CO2 from the smokestacks of a coal-fired plant before it enters the atmosphere, transport the CO2 through pipelines, and inject the CO2 underground into a carefully selected and suitable subsurface geological formation, such as a field of oil abandoned nearby, where it is safely stored.
Methane Emissions
In 2020, methane (CH4) was responsible for about 11% of all greenhouse gas emissions from human activities. Human activities that emit methane include leaking natural gas systems and raising livestock. Methane is also emitted from natural sources such as natural swamps. In addition, natural processes in the soil and chemical reactions in the atmosphere help to remove CH4 from the atmosphere. The lifetime of methane in the atmosphere is much shorter than that of carbon dioxide (CO2), but CH4 is more efficient at capturing radiation than CO2. Kilogram for Kilogram, the comparative impact of CH4 is 25 times greater than that of CO2 over a 100-year period.
Globally, 50-65% of total CH4 emissions come from human activities. Methane is emitted by energy, industry, agriculture, land use and waste management activities, described below.
• Agriculture. Domestic animals such as cattle, pigs, sheep and goats produce CH4 as part of their normal digestive process. In addition, when animal manure is stored or handled in ponds or holding tanks, CH4 is produced. As humans raise these animals for food and other products, the emissions are considered human-related. The agricultural sector is the biggest source of CH4 emissions. CH4 emissions also occur as a result of land use and land management activities in the Land Use, Land Use Change and Forestry sector (e.g. forest and grassland fires, decomposition of organic matter in coastal wetlands ).
• Energy and Industry. Natural gas and oil systems are the second largest source of CH4 emissions. Methane is the main component of natural gas. Methane is emitted into the atmosphere during the production, processing, storage, transmission and distribution of natural gas and the production, refinement, transport and storage of crude oil. Coal mining is also a source of CH4 emissions.
• Waste from homes and businesses. Methane is generated in landfills as waste decomposes and in wastewater treatment. Landfills are the third largest source of CH4 emissions. Methane is also generated from the treatment of domestic and industrial effluents and from composting and anaerobic digestion.
Methane is also emitted from various natural sources. Natural wetlands are the biggest source, emitting CH4 from bacteria that break down organic materials in the absence of oxygen. Smaller sources include termites, oceans, sediment, volcanoes and wildfires.
Reduction of methane emissions
There are several ways to reduce CH4 emissions. Some examples are shown below.
Industry
Upgrading equipment used to produce, store and transport oil and natural gas can reduce many of the leaks that contribute to CH4 emissions. Methane from coal mines can also be captured and used as energy.
Agriculture
Methane from manure management practices can be reduced and captured by changing manure management strategies. In addition, changes in animal feeding practices can reduce emissions from enteric fermentation.
Waste from homes and businesses
As CH4 emissions from landfill gas are a major source of CH4 emissions, emission controls that capture CH4 from the landfill are an effective reduction strategy.