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OverviewTotal Emissions in 2020 = 5,981 Million Metric Tons of CO2 equivalent. Percentages may not add up to 100% due to independent rounding.* Land Use, Land-Use Change, and Forestry in the United States is a net sink and removes approximately 13% of these greenhouse gas emissions. This net sink is not shown in the above diagram. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020. Larger image to save or print Greenhouse gases trap heat and make the planet warmer. Human activities are responsible for almost all of the increase in greenhouse gases in the atmosphere over the last 150 years.1 The largest source of greenhouse gas emissions from human activities in the United States is from burning fossil fuels for electricity, heat, and transportation. EPA tracks total U.S. emissions by publishing the Inventory of U.S. Greenhouse Gas Emissions and Sinks. This annual report estimates the total national greenhouse gas emissions and removals associated with human activities across the United States. The primary sources of greenhouse gas emissions in the United States are:
Emissions and TrendsSince 1990, gross U.S. greenhouse gas emissions have decreased by 7%. From year to year, emissions can rise and fall due to changes in the economy, the price of fuel, and other factors. In 2020, U.S. greenhouse gas emissions decreased 11% compared to 2019 levels. The sharp decline in emissions was primarily from CO2 emissions from fossil fuel combustion and was largely due to the coronavirus (COVID-19) pandemic-related reductions in travel and economic activity, including a 13% decrease in transportation emissions driven by less travel due to the COVID-19 pandemic. Electric power sector emissions decreased 10% due to a slight decrease in electricity demand from the COVID-19 pandemic and a continued shift from coal to less carbon-intensive natural gas and renewables. Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print References
Electric Power Sector EmissionsTotal Emissions in 2020 = 5,981 Million Metric Tons of CO2 equivalent. Percentages may not add up to 100% due to independent rounding.* Land Use, Land-Use Change, and Forestry in the United States is a net sink and removes approximately 13% of these greenhouse gas emissions. This net sink is not shown in the above diagram. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020. Larger image to save or print The Electricity sector involves the generation, transmission, and distribution of electricity. Carbon dioxide (CO2) makes up the vast majority of greenhouse gas emissions from the sector, but smaller amounts of methane (CH4) and nitrous oxide (N2O) are also emitted. These gases are released during the combustion of fossil fuels, such as coal, oil, and natural gas, to produce electricity. Less than 1% of greenhouse gas emissions from the sector come from sulfur hexafluoride (SF6), an insulating chemical used in electricity transmission and distribution equipment. Greenhouse Gas Emissions in the Electric Power Sector by Fuel SourceCoal combustion is more carbon-intensive than burning natural gas or petroleum for electric power production. Although coal use accounted for about 54% of CO2 emissions from the sector, it represented only 20% of the electricity generated in the United States in 2020. Natural gas use accounted for 39% of electricity generation in 2020, and petroleum use accounted for less than 1%. The remaining generation in 2020 came from non-fossil fuel sources, including nuclear (21%) and renewable energy sources (20%), which include hydroelectricity, biomass, wind, and solar.1 Most of these non-fossil sources, such as nuclear, hydroelectric, wind, and solar, are non-emitting. Emissions and TrendsIn 2020, the electric power sector was the second largest source of U.S. greenhouse gas emissions, accounting for 25% of the U.S. total. Electric power sector emissions decreased 10% from 2019 due to a slight decrease in electricity demand from the COVID-19 pandemic and a continued shift from coal to less carbon-intensive natural gas and renewables. Greenhouse gas emissions from electric power production have decreased by about 21% since 1990 due to a shift in generation to lower- and non-emitting sources of electricity generation and an increase in end-use energy efficiency. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print Greenhouse Gas Emissions by Electricity End-UsePercentages may not add up to 100% due to independent rounding. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print Electricity is used by other sectors—in homes, businesses, and factories, the greenhouse gas emissions from electricity generation can be attributed to the sectors that use the electricity. Looking at greenhouse gas emissions by end-use sector can help us understand energy demand across sectors and changes in energy use over time. When emissions from electric power production are allocated to the industrial end-use sector, industrial activities account for a much larger share of U.S. greenhouse gas emissions. Greenhouse gas emissions from commercial and residential buildings also increase substantially when emissions from electricity end-use are included, due to the relatively large share of electricity use (e.g., heating, ventilation, and air conditioning; lighting; and appliances) in these sectors. The transportation sector currently has a relatively low percentage of electricity use, but it is growing due to the use of electric and plug-in vehicles. Reducing Emissions from Electric Power ProductionThere are a variety of opportunities to reduce greenhouse gas emissions associated with electric power production, transmission, and distribution. The table below categorizes these opportunities and provides examples. For a more comprehensive list, see Chapter 7 (PDF)(88 pp, 3.6MB) of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.2 Example Reduction Opportunities for the Electric Power Sector
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Transportation Sector EmissionsTotal Emissions in 2020 = 5,981 Million Metric Tons of CO2 equivalent. Percentages may not add up to 100% due to independent rounding.* Land Use, Land-Use Change, and Forestry in the United States is a net sink and removes approximately 13% of these greenhouse gas emissions. This net sink is not shown in the above diagram. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020. Larger image to save or print The Transportation sector includes the movement of people and goods by cars, trucks, trains, ships, airplanes, and other vehicles. The majority of greenhouse gas emissions from transportation are carbon dioxide (CO2) emissions resulting from the combustion of petroleum-based products, like gasoline and diesel fuel, in internal combustion engines. The largest sources of transportation-related greenhouse gas emissions include passenger cars, medium- and heavy-duty trucks, and light-duty trucks, including sport utility vehicles, pickup trucks, and minivans. These sources account for over half of the emissions from the transportation sector. The remaining greenhouse gas emissions from the transportation sector come from other modes of transportation, including commercial aircraft, ships, boats, and trains, as well as pipelines and lubricants. Relatively small amounts of methane (CH4) and nitrous oxide (N2O) are emitted during fuel combustion. In addition, a small amount of hydrofluorocarbon (HFC) emissions are included in the Transportation sector. These emissions result from the use of mobile air conditioners and refrigerated transport. Emissions and TrendsIn 2020, greenhouse gas emissions from transportation accounted for about 27% of total U.S. greenhouse gas emissions, making it the largest contributor of U.S. greenhouse gas emissions. From 2019 to 2020, transportation sector GHG emissions decreased 13%, primarily a result of the COVID-19 pandemic and associated restrictions that led to less travel. During this period, GHG emissions from passenger transportation decreased by 16%, while GHG emissions from domestic freight transportation saw a 6% decrease. In terms of the overall trend, from 1990 to 2020, total transportation emissions have increased due, in large part, to increased demand for travel. The number of vehicle miles traveled (VMT) by light-duty motor vehicles (passenger cars and light-duty trucks) increased by 30% from 1990 to 2020, as a result of a confluence of factors including population growth, economic growth, urban sprawl, and periods of low fuel prices. Between 1990 and 2004, average fuel economy among new vehicles sold annually declined, as sales of light-duty trucks increased. Starting in 2005, average new vehicle fuel economy began to increase, while light-duty VMT grew only modestly for much of the period. Average new vehicle fuel economy has improved almost every year since 2005, slowing the rate of increase of CO2 emissions. The light-duty truck share is about 56% of new vehicles in model year 2020. Learn more about Greenhouse Gas Emissions from Transportation. Larger image to save or print Reducing Emissions from TransportationThere are a variety of opportunities to reduce greenhouse gas emissions associated with transportation. The table shown below categorizes these opportunities and provides examples. For a more comprehensive list, see Chapter 8 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.1 Examples of Reduction Opportunities in the Transportation Sector
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Industry Sector EmissionsTotal Emissions in 2020 = 5,981 Million Metric Tons of CO2 equivalent. Percentages may not add up to 100% due to independent rounding.* Land Use, Land-Use Change, and Forestry in the United States is a net sink and removes approximately 13% of these greenhouse gas emissions. This net sink is not shown in the above diagram. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020. Larger image to save or print The Industry sector produces the goods and raw materials we use every day. The greenhouse gases emitted during industrial production are split into two categories: direct emissions that are produced at the facility, and indirect emissions that occur off site but are associated with the facility's use of electricity. Direct emissions are produced by burning fuel for power or heat, through chemical reactions, and from leaks from industrial processes or equipment. Most direct emissions come from the consumption of fossil fuels for energy. A smaller amount of direct emissions, roughly one third, come from leaks from natural gas and petroleum systems, the use of fuels in production (e.g., petroleum products used to make plastics), and chemical reactions during the production of chemicals, metals (e.g., iron and steel), and minerals (e.g., cement). Indirect emissions are produced by burning fossil fuel at a power plant to make electricity, which is then used by an industrial facility to power industrial buildings and machinery. More information about facility-level emissions from large industrial sources is available through EPA's Greenhouse Gas Reporting Program's data publication tool. National-level information about emissions from industry as a whole can be found in the sections on Fossil Fuel Combustion and the Industrial Processes chapter in the Inventory of U.S. Greenhouse Gas Emissions and Sinks. Emissions and TrendsIn 2020, direct industrial greenhouse gas emissions accounted for 24% of total U.S. greenhouse gas emissions, making it the third largest contributor to U.S. greenhouse gas emissions, after the Transportation and Electric Power sectors. From 2019 to 2020, total energy use in the industrial sector decreased by 5% partially as a result of reductions in economic and manufacturing activity due to the COVID-19 pandemic. Including both direct emissions and indirect emissions associated with electricity use, industry's share of total U.S. greenhouse gas emissions in 2020 was 30%, making it the largest contributor of greenhouse gases of any sector. Total U.S. greenhouse gas emissions from industry, including electricity, have declined by 22% since 1990. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print Reducing Emissions from IndustryThere are a wide variety of industrial activities that cause greenhouse gas emissions, and many opportunities to reduce them. The table shown below provides some examples of opportunities for industry to reduce emissions. For a more comprehensive list, see Chapter 10 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. 1 Examples of Reduction Opportunities for the Industry Sector
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Commercial and Residential Sector EmissionsTotal Emissions in 2020 = 5,981 Million Metric Tons of CO2 equivalent. Percentages may not add up to 100% due to independent rounding.* Land Use, Land-Use Change, and Forestry in the United States is a net sink and removes approximately 13% of these greenhouse gas emissions. This net sink is not shown in the above diagram. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020. Larger image to save or print The residential and commercial sectors include all homes and commercial businesses (excluding agricultural and industrial activities). Greenhouse gas emissions from this sector come from direct emissions including fossil fuel combustion for heating and cooking needs, management of waste and wastewater, and leaks from refrigerants in homes and businesses as well as indirect emissions that occur offsite but are associated with use of electricity consumed by homes and businesses. Direct emissions are produced from residential and commercial activities in a variety of ways:
Indirect emissions are produced by burning fossil fuel at a power plant to make electricity, which is then used in residential and commercial activities such as lighting and for appliances. More national-level information about emissions from the residential and commercial sectors can be found in the U.S. Inventory's Energy and Trends chapters. Emissions and TrendsIn 2020, direct greenhouse gas emissions from homes and businesses accounted for 13% of total U.S. greenhouse gas emissions. Greenhouse gas emissions from homes and businesses vary from year to year often correlated with seasonal fluctuations in energy use caused primarily by weather conditions. Total residential and commercial greenhouse gas emissions, including direct and indirect emissions, in 2020 have decreased by 5% since 1990. Greenhouse gas emissions from on-site direct emissions in homes and businesses have increased by 2% since 1990. Additionally, indirect emissions from electricity use by homes and businesses increased from 1990 to 2007, but have decreased since then to approximately 10% below 1990 levels in 2020. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print Reducing Emissions from Homes and BusinessesThe table shown below provides examples of opportunities to reduce emissions from homes and businesses. For a more comprehensive list of options and a detailed assessment of how each option affects different gases, see Chapter 9 and Chapter 12 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Examples of Reduction Opportunities in the Residential and Commercial Sector
Agriculture Sector EmissionsTotal Emissions in 2020 = 5,981 Million Metric Tons of CO2 equivalent. Percentages may not add up to 100% due to independent rounding.* Land Use, Land-Use Change, and Forestry in the United States is a net sink and removes approximately 13% of these greenhouse gas emissions. This net sink is not shown in the above diagram. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020. Larger image to save or print Agricultural activities — crop and livestock production for food — contribute to emissions in a variety of ways:
More information about emissions from agriculture can be found in the agriculture chapter in the Inventory of U.S. Greenhouse Gas Emissions and Sinks. * Management of croplands and grasslands can also lead to emissions or sequestration of carbon dioxide (CO2). These emissions and removals are included under the Land Use, Land-Use Change, and Forestry sector. Emissions and TrendsIn 2020, greenhouse gas emissions from the agriculture economic sector accounted for 11% of total U.S. greenhouse gas emissions. Greenhouse gas emissions from agriculture have increased by 6% since 1990. This increase is largely driven by a 62% growth in combined CH4 and N2O emissions from livestock manure management systems, reflecting the increased use of emission-intensive liquid systems over this time period. Emissions from other agricultural sources have generally remained flat or changed by a relatively small amount since 1990. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print Reducing Emissions from AgricultureThe table shown below provides examples of opportunities to reduce emissions from agriculture. For a more comprehensive list of options and a detailed assessment of how each option affects different gases, see Chapter 11 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Examples of Reduction Opportunities for the Agriculture Sector
Land Use, Land-Use Change, and Forestry Sector Emissions and SequestrationPlants absorb carbon dioxide (CO2) from the atmosphere as they grow, and they store some of this carbon as aboveground and belowground biomass throughout their lifetime. Soils and dead organic matter/litter can also store some of the carbon from these plants depending on how the soil is managed and other environmental conditions (e.g., climate). This storage of carbon in plants, dead organic matter/litter and soils is called biological carbon sequestration. Because biological sequestration takes CO2 out of the atmosphere and stores it in these carbon pools, it is also called a carbon "sink." Emissions or sequestration of CO2, as well as emissions of CH4 and N2O can occur from management of lands in their current use or as lands are converted to other land uses. Carbon dioxide is exchanged between the atmosphere and the plants and soils on land, for example, as cropland is converted into grassland, as lands are cultivated for crops, or as forests grow. In addition, using biological feedstocks (such as energy crops or wood) for purposes such as electricity generation, as inputs to processes that create liquid fuels, or as building materials can lead to emissions or sequestration.* In the United States overall, Land Use, Land-Use Change, and Forestry (LULUCF) activities have resulted in more removal of CO2 from the atmosphere than emissions. Because of this, the LULUCF sector in the United States is considered a net sink, rather than a source, of CO2. In many areas of the world, the opposite is true, particularly in countries where large areas of forest land are cleared, often for conversion to agricultural purposes or for settlements. In these situations, the LULUCF sector can be a net source of greenhouse gas emissions.
* Emissions and sequestration of CO2 are presented under the Land Use, Land-Use Change, and Forestry sector in the Inventory. Emissions of methane (CH4) and nitrous oxide (N2O) also occur as a result of land use and management activities in the LULUCF sector. Other emissions from CH4 and N2O are also presented in the Energy sector. Emissions and TrendsIn 2020, the net CO2 removed from the atmosphere from the LULUCF sector was 14% of total U.S. greenhouse gas emissions. Between 1990 and 2020, total carbon sequestration in the LULUCF sector decreased by 9%, primarily due to a decrease in the rate of net carbon accumulation in forests, as well as an increase in CO2 emissions from urbanization. Additionally, while episodic in nature, increased CO2, CH4 and N2O emissions from forest fires have also occurred over the time series. *Note: The LULUCF sector is a net "sink" of emissions in the United States (e.g., more greenhouse gas emissions are sequestered than emitted from land use activities), so net greenhouse gas emissions from LULUCF are negative. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2020.Larger image to save or print Reducing Emissions and Enhancing Sinks from Land Use, Land-Use Change, and ForestryIn the LULUCF sector, opportunities exist to reduce emissions and increase the potential to sequester carbon from the atmosphere by enhancing sinks. The table shown below provides some examples of opportunities for both reducing emissions and enhancing sinks. For a more comprehensive list, see Chapter 11 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Examples of Reduction Opportunities in the LULUCF Sector
Which energy source contributes the most to climate change apex?Answer and Explanation: Fossil fuels contribute most to climate change. Fossil fuels are an energy source made of long-dead organisms that have been compressed into hydrocarbon-rich forms such as coal, oil, and natural gas.
Which energy source is the biggest polluter?This includes deaths from air pollution and accidents in the supply chain. Let's look at this comparison in the chart. Fossil fuels and biomass kill many more people than nuclear and modern renewables per unit of electricity. Coal is, by far, the dirtiest.
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