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In 2016, the transportation sector caused 28.5% of emissions, with fossil fuels being the culprit. The typical passenger vehicle will emit 4.6 metric tons of carbon dioxide a year, not even counting what is used to create said car. With millions of cars being created and driven every year, these metric tons add up.

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A typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year. This number can vary based on a vehicle's fuel, fuel economy, and the number of miles driven per year. Click on the questions below to learn more about this estimate and see answers to common questions about greenhouse gas emissions from passenger vehicles.

How much tailpipe carbon dioxide (CO₂) is created from burning one gallon of fuel?

CO₂ emissions from a gallon of gasoline: 8,887 grams CO₂/ gallon

CO₂ emissions from a gallon of diesel: 10,180 grams CO₂/ gallon

Most of the weight of the CO ₂ doesn't come from the gasoline itself, but the oxygen in the air. When gasoline burns, the carbon and hydrogen separate. The hydrogen combines with oxygen to form water (H ₂O), and carbon combines with oxygen to form carbon dioxide (CO ₂). Visit fueleconomy.gov for more details, including the calculations.

How much tailpipe carbon dioxide (CO₂) is emitted from driving one mile?
The average passenger vehicle emits about 400 grams of CO₂ per mile.

What is the average annual carbon dioxide (CO₂) emissions of a typical passenger vehicle?

A typical passenger vehicle emits about 4.6 metric tons of CO₂ per year.

This assumes the average gasoline vehicle on the road today has a fuel economy of about 22.2 miles per gallon and drives around 11,500 miles per year. Every gallon of gasoline burned creates about 8,887 grams of CO₂.

Are there other sources of greenhouse gas (GHG) emissions from a vehicle?
In addition to carbon dioxide (CO₂), automobiles using gasoline produce methane (CH₄) and nitrous oxide (N₂O) from the tailpipe and all vehicles can emit hydrofluorocarbon (HFC) from leaking air conditioners. For gasoline vehicles, the emissions of HFCs are small in comparison to CO₂; however, the impact of these emissions can be important because they have a higher global warming potential (GWP) than CO₂. Electric vehicles (EVs) also emit a small amount of GHGs due to air conditioner/HFC leakage.

What are the tailpipe emissions from a plug-in hybrid electric vehicle (PHEV) or an electric vehicle (EV)? What about hydrogen fuel cell vehicles?

Electric vehicles (EVs) have a battery instead of a gasoline tank, and an electric motor instead of an internal combustion engine. EVs do not emit any tailpipe emissions. A fuel cell electric vehicle (FCEV) operating on hydrogen will emit only water vapor.

Calculating tailpipe emissions for PHEVs is more complicated because they use both gasoline and electricity as fuel sources. When operating on electricity only, a PHEV does not generate any tailpipe emissions. When a PHEV is operating on gasoline only, it creates tailpipe emissions based on its gasoline fuel economy. Tailpipe emissions for a PHEV operating on both electricity and gasoline cannot be calculated without detailed information about how the specific PHEV operates. The overall tailpipe emissions for a PHEV can vary significantly based on its battery capacity, how it is driven, and how often it is charged.

For more information, see the " My Plug-In Hybrid " calculator.

Are there any greenhouse gas (GHG) emissions associated with the use of my vehicle other than what comes out of the tailpipe?

Driving gasoline vehicles results in tailpipe GHG emissions. Producing and distributing the gasoline used to power your vehicle also creates GHGs. For example, the production of gasoline requires extracting oil from the ground, transporting it to a refinery, refining the oil into gasoline, and transporting the gasoline to service stations. Each of these steps can produce additional GHGs.

Electric vehicles (EVs) have no tailpipe emissions; however, emissions are created during both the production and distribution of the electricity used to fuel the vehicle. Visit the Beyond Tailpipe Emissions calculator to estimate GHG emissions for an EV in your region of the country.

I thought my gasoline was blended with ethanol. Does that change my tailpipe carbon dioxide (CO₂) emissions?
Most of the gasoline sold in the U.S. is a mixture of gasoline and up to 10% ethanol (often referred to as E10). The exact formulation of the gasoline in your vehicle will vary depending on season, region in the U.S., and other factors. While your fuel economy when using an ethanol blend in your vehicle will be slightly lower than when using gasoline without ethanol, the CO₂ tailpipe emissions per mile will be similar. This is because ethanol has less carbon per gallon than gasoline.

How does EPA measure carbon dioxide (CO₂) emissions from vehicles?

EPA and automobile manufacturers measure vehicle fuel economy and CO₂ emissions using a set of standardized laboratory tests. These tests were designed by EPA to mimic typical driving patterns. Both EPA and the Department of Transportation use these values to ensure that manufacturers meet federal greenhouse gas and corporate average fuel economy (CAFE) standards.

For every new vehicle, the test results are used to determine real world fuel economy and CO₂ emissions. These adjusted results are used on the Fuel Economy and Environment Labels and on Fueleconomy.gov.

How can I find and compare carbon dioxide (CO₂) emission rates for specific vehicle models?

Visit Fueleconomy.gov and click on "Find a Car." Select your vehicle of interest. From the vehicle search results page, click on the "Energy and Environment" tab. A vehicle's GHG emissions rate (g/mile) and GHG rating (1-10 scale) can be found on that search results page.

When shopping at a dealership, check out tailpipe CO₂ emission rates on vehicle Fuel Economy and Environment Labels. The labels also feature a 1-to 10 Fuel Economy and GHG rating to enable easy comparison shopping.

Other useful sources include:

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Greenhouse Gas Emissions from a Typical Passenger Vehicle | US EPA

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This page answers questions about GHG emissions from passenger vehicles and how these emissions are measured and calculated.

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In 2016, the production of electricity and the burning of fossil fuels equally cause 28% of carbon emissions. Electric cars are the solution to this. If we replaced gas with electricity, we would massively decrease the amount of fuel burned. Admittedly, carbon emitted from creating the electricity would increase, but in the long run we would benefit.

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Agriculture took up only 9% of emissions in 2016, mostly due to carbon emitted from animals, particularly cows. When cows "do their business" they expel methane, which contributes to carbon emissions. As more people are born, more food will be needed, which means more cows will be needed and born, which means more methane is released. Right now, cows account for about a third of agricultural carbon, which is likely to increase.

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Overview

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. 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:

(nearly 28.5 percent of 2016 greenhouse gas emissions) - The transportation sector generates the largest share of greenhouse gas emissions. Greenhouse gas emissions from transportation primarily come from burning fossil fuel for our cars, trucks, ships, trains, and planes. Over 90 percent of the fuel used for transportation is petroleum based, which includes gasoline and diesel.

(28.4 percent of 2016 greenhouse gas emissions) - Electricity production generates the second largest share of greenhouse gas emissions. Approximately 68 percent of our electricity comes from burning fossil fuels, mostly coal and natural gas.

(22 percent of 2016 greenhouse gas emissions) - Greenhouse gas emissions from industry primarily come from burning fossil fuels for energy, as well as greenhouse gas emissions from certain chemical reactions necessary to produce goods from raw materials.

(11 percent of 2016 greenhouse gas emissions) - Greenhouse gas emissions from businesses and homes arise primarily from fossil fuels burned for heat, the use of certain products that contain greenhouse gases, and the handling of waste.

(9 percent of 2016 greenhouse gas emissions) - Greenhouse gas emissions from agriculture come from livestock such as cows, agricultural soils, and rice production.

(offset of 11 percent of 2016 greenhouse gas emissions) - Land areas can act as a sink (absorbing CO₂ from the atmosphere) or a source of greenhouse gas emissions. In the United States, since 1990, managed forests and other lands have absorbed more CO₂ from the atmosphere than they emit.

Emissions and Trends

Since 1990, gross U.S. greenhouse gas emissions have increased by about 2 percent. From year to year, emissions can rise and fall due to changes in the economy, the price of fuel, and other factors. In 2016, U.S. greenhouse gas emissions decreased compared to 2015 levels. This decrease was largely driven by a decrease in emissions from fossil fuel combustion, which was a result of multiple factors including substitution from coal to natural gas consumption in the electric power sector; warmer winter conditions that reduced demand for heating fuel in the residential and commercial sectors.

References
¹ IPCC (2007). Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Exit Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

² Kahn Ribeiro, S., S. Kobayashi, M. Beuthe, J. Gasca, D. Greene, D. S. Lee, Y. Muromachi, P. J. Newton, S. Plotkin, D. Sperling, R. Wit, P. J. Zhou (2007). Transport and its infrastructure. In Climate Change 2007: Mitigation. Exit Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds.)], Cambridge University Press, Cambridge, United Kingdom.

3 U.S. Energy Information Administration (2016). Electricity Explained - Basics
Electricity Sector Emissions

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 percent 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 Electricity Sector by Fuel Source

Coal combustion is more carbon intensive than burning natural gas or petroleum for electricity. Although coal accounted for about 67 percent of CO ₂ emissions from the sector, it represented only about 32 percent of the electricity generated in the United States in 2016. Another 33 percent of electricity generated in 2016 was generated using natural gas, an increase relative to 2015. Petroleum accounted for less than 1 percent of electricity generation in 2016. The remaining generation in 2016 came from non-fossil fuel sources including nuclear (about 21 percent) and renewable sources (about 14 percent), which include hydroelectricity, biomass, wind, and solar. These other sources usually release fewer greenhouse gas emissions than fossil fuel combustion, if any emissions at all.

Emissions and Trends

In 2016, the electricity sector was the second largest source of U.S. greenhouse gas emissions, accounting for about 28.4 percent of the U.S. total. Greenhouse gas emissions from electricity have decreased by about 1 percent since 1990 due to fuel switching to lower emitting sources of electricity production.
1. U.S. Energy Information Administration (2016). Electricity Explained - Basics.
Greenhouse Gas Emissions by Electricity End-Use

Electricity is consumed by other sectorsin homes, businesses, and factories. Therefore, it is possible to attribute the greenhouse gas emissions from electricity production 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 electricity are allocated to the end-use sector, industrial activities account for a much larger share of U.S. greenhouse gas emissions. Emissions from commercial and residential buildings also increase substantially when emissions from electricity are included, due to their relatively large share of electricity consumption (e.g., lighting and appliances).

Reducing Emissions from Electricity

There are a variety of opportunities to reduce greenhouse gas emissions associated with electricity generation, transmission, and distribution. The table shown below categorizes these opportunities and provides examples. For a more comprehensive list, see Chapter 7 of the Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Exit

Increased Efficiency of Power Plants and Fuel Switching

Increasing efficiency of existing power plants by using advanced technologies or substituting fuels that combust more efficiently.

Converting a conventional coal-powered steam turbine into an advanced turbine that uses pulverized coal.

Converting a coal-powered turbine into a natural gas-powered turbine.

Converting a single-cycle turbine into a combined-cycle turbine.

Renewable Energy

Using renewable energy sources rather than fossil fuel to generate electricity.

Increasing the share of total electricity generated from wind, solar, hydro, and geothermal sources and from certain biofuel sources.

Increased Energy Efficiency (end-use)

Reducing energy demand by increasing efficiency and conservation in homes, businesses, and industry.

EPA's ENERGY STAR® partners removed over 320 million metric tons of greenhouse gases in 2016 alone, and helped Americans save over $30 billion in energy costs, approximately 400 billion kWh of electricity.

Nuclear Energy

Generating electricity from nuclear processes rather than the combustion of fossil fuels.

Building nuclear power plants as fossil fuel power plants are retired.

Carbon Capture Sequestration and Storage (CCS)

Capturing CO ₂ as a byproduct of fossil fuel combustion before it enters the atmosphere and then transferring the CO ₂ to a long-term storage area, such as an underground geologic formation.

Capturing CO ₂ from the stacks of a coal-fired power plant, and then transferring the CO ₂ via pipeline to a nearby abandoned oil field where the CO ₂ is injected underground. Learn more about CCS.

Reference

Transportation Sector Emissions

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, in internal combustion engines. The largest sources of transportation-related greenhouse gas emissions include passenger cars 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 freight trucks, 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 Trends

In 2016, greenhouse gas emissions from transportation accounted for about 28.5 percent of total U.S. greenhouse gas emissions, making it the largest contributor of U.S. greenhouse gas emissions. In terms of the overall trend, from 1990 to 2016, total transportation emissions 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 approximately 45 percent from 1990 to 2016, 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, and the truck share is about 43 percent of new vehicles in model year 2015.

Learn more about Greenhouse Gas Emissions from Transportation.

Reducing Emissions from Transportation

There 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. Exit

EPA's light-duty vehicle greenhouse gas rules are projected to save consumers $1.7 trillion at the pump by 2025, and eliminate 6 billion metric tons of greenhouse gas pollution.

Fuel Switching

Using fuels that emit less CO ₂ than fuels currently being used. Alternative sources can include biofuels; hydrogen; electricity from renewable sources, such as wind and solar; or fossil fuels that are less CO ₂-intensive than the fuels that they replace.

Learn more about Green Vehicles and Alternative and Renewable Fuels.

Using public buses that are fueled by compressed natural gas rather than gasoline or diesel.

Using electric or hybrid automobiles, provided that the energy is generated from lower-carbon or non-fossil fuels.

Using renewable fuels such as low-carbon biofuels.

Improving Fuel Efficiency with Advanced Design, Materials, and Technologies

Using advanced technologies, design, and materials to develop more fuel-efficient vehicles.

Learn about EPA's vehicle greenhouse gas rules.

Developing advanced vehicle technologies such as hybrid vehicles and electric vehicles, that can store energy from braking and use it for power later.

Reducing the weight of materials used to build vehicles.

Reducing the aerodynamic resistance of vehicles through better shape design.

Improving Operating Practices

Adopting practices that minimize fuel use.
Improving driving practices and vehicle maintenance.

Learn about how the freight transportation industry can reduce emissions through EPA's SmartWay Program.

Reducing the average taxi time for aircraft.

Driving sensibly (avoiding rapid acceleration and braking, observing the speed limit).

Reducing engine-idling.

Improved voyage planning for ships, such as through improved weather routing, to increase fuel efficiency.

Reducing Travel Demand

Employing urban planning to reduce the number of miles that people drive each day.

Reducing the need for driving through travel efficiency measures such as commuter, biking, and pedestrian programs.

Learn about EPA's Smart Growth Program.

Building public transportation, sidewalks, and bike paths to increase lower-emission transportation choices.

Zoning for mixed use areas, so that residences, schools, stores, and businesses are close together, reducing the need for driving.

Industry Sector Emissions

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 energy.

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, roughly a 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, iron and steel, and 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 Trends

In 2016, direct industrial greenhouse gas emissions accounted for approximately 22 percent of total U.S. greenhouse gas emissions, making it the third largest contributor to U.S. greenhouse gas emissions, after the and sectors. If both direct and indirect emissions associated with electricity use are included, industry's share of total U.S. greenhouse gas emissions in 2016 was 29 percent, making it the largest contributor of greenhouse gases of any sector. Greenhouse gas emissions from industry have declined by almost 14 percent since 1990, while emissions from most other sectors have increased.

Reducing Emissions from Industry

There 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. Exit

Energy Efficiency

Upgrading to more efficient industrial technology.
EPA's ENERGY STAR® program helps industries become more energy-efficient.

Identifying the ways that (87 pp, 1 M, manufacturers About PDF) can use less energy to light and heat factories or to run equipment.

Fuel Switching

Switching to fuels that result in less CO ₂ emissions but the same amount of energy, when combusted.

Using natural gas instead of coal to run machinery.

Recycling

Producing industrial products from materials that are recycled or renewable, rather than producing new products from raw materials.

Using scrap steel and scrap aluminum as opposed to smelting new aluminum or forging new steel.

Training and Awareness

Making companies and workers aware of the steps to reduce or prevent emissions leaks from equipment.
EPA has a variety of voluntary programs that provide resources for training and other steps for reducing emissions. EPA supports programs for the aluminum, semiconductor, and magnesium industries.

Instituting handling policies and procedures for perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF ₆) that reduce occurrences of accidental releases and leaks from containers and equipment.

Commercial and Residential Sector Emissions

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:

Combustion of natural gas and petroleum products for heating and cooking needs emits carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Emissions from natural gas consumption represent about 78 percent of the direct fossil fuel CO₂ emissions from the residential and commercial sectors. Coal consumption is a minor component of energy use in both of these sectors.

Organic waste sent to landfills emits CH₄.

Wastewater treatment plants emit CH₄ and N₂O.

Fluorinated gases (mainly hydrofluorocarbons, or HFCs) used in air conditioning and refrigeration systems can be released during servicing or from leaking equipment.

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.
¹ EPA (2012). Energy Efficiency for Water and Wastewater Utilities. Accessed 03/13/2012
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 Trends

In 2016, direct greenhouse gas emissions from homes and businesses accounted for approximately 11 percent of total U.S. greenhouse gas emissions. Greenhouse gas emissions from homes and businesses vary from year to year based on short-term fluctuations in energy consumption caused primarily by weather conditions. Total residential and commercial greenhouse gas emissions in 2016 have increased by about 7 percent since 1990. Greenhouse gas emissions from on-site direct emissions in homes and businesses have decreased by about 3 percent since 1990. Additionally, indirect emissions from use by homes and businesses have increased by 14 percent since 1990, due to increasing electricity consumption for lighting, heating, air conditioning, and appliances.

Reducing Emissions from Homes and Businesses

The table shown below provides some 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. Exit

Homes and Commercial Buildings

Reducing energy use through energy efficiency.

Homes and commercial buildings use large amounts of energy for heating, cooling, lighting, and other functions. "Green building" techniques and retrofits can allow new and existing buildings to use less energy to accomplish the same functions, leading to fewer greenhouse gas emissions. Techniques to improve building energy efficiency include better insulation; more energy-efficient heating, cooling, ventilation, and refrigeration systems; efficient fluorescent lighting; passive heating and lighting to take advantage of sunlight; and the purchase of energy-efficient appliances and electronics. Learn more about ENERGY STAR®.

Wastewater Treatment

Making water and wastewater systems more energy-efficient.

Drinking water and wastewater systems account for approximately 3 percent to 4 percent of energy use in the United States. Studies estimate potential savings of 15 percent to 30 percent that are "readily achievable" in water and wastewater plants.
Learn more about Energy Efficiency for Water and Wastewater Utilities.

Waste Management

Reducing solid waste sent to landfills.
Capturing and using methane produced in current landfills.

Landfill gas is the natural byproduct of the decomposition of solid waste in landfills. It primarily consists of CO ₂ and CH ₄.
Well established, low-cost methods to reduce greenhouse gases from consumer waste exist, including recycling programs, waste reduction programs, and landfill methane capture programs.

Refrigeration

Reducing leakage from refrigeration equipment.
Using refrigerants with lower global warming potentials.

Commonly used refrigerants include ozone-depleting hydrochlorofluorocarbon (HCFC) refrigerants, often HCFC-22, and blends consisting entirely or primarily of hydrofluorocarbons (HFCs), both of which are potent greenhouse gases. In recent years there have been several advancements in refrigeration technology that can help food retailers reduce both refrigerant charges and refrigerant emissions.
Learn more about EPA's GreenChill Program to reduce greenhouse gas emissions from commercial refrigerators.

References

Agriculture Sector Emissions

Agricultural activities - crop and livestock production for food - contribute to emissions in a variety of ways:

Various management practices on agricultural soils can lead to increased availability of nitrogen in the soil and result in emissions of nitrous oxide (N₂O). Specific activities that contribute to N₂O emissions from agricultural lands include the application of synthetic and organic fertilizers, the growth of nitrogen-fixing crops, the drainage of organic soil, and irrigation practices. Management of agricultural soils accounts for over half of the emissions from the Agriculture economic sector.*

Livestock, especially ruminants such as cattle, produce methane (CH₄) as part of their normal digestive processes. This process is called enteric fermentation, and it represents almost one third of the emissions from the Agriculture economic sector.

The way in which manure from livestock is managed also contributes to CH₄ and N₂O emissions. Different manure treatment and storage methods affect how much of these greenhouse gases are produced. Manure management accounts for about 15 percent of the total greenhouse gas emissions from the Agriculture economic sector in the United States.

Smaller sources of agricultural emissions include CO₂ from liming and urea application, CH4 from rice cultivation, and burning crop residues, which produces CH₄ and N₂O.

More national-level 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). However, these emissions and removals are included under the .

Emissions and Trends

In 2016, greenhouse gas emissions from the agriculture economic sector accounted for approximately 9 percent of total U.S. greenhouse gas emissions. Greenhouse gas emissions from agriculture have increased by approximately 17 percent since 1990. One driver for this increase has been the 68 percent growth in combined CH ₄ and N ₂ O 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 either remained flat or changed by a relatively small amount since 1990.

Reducing Emissions from Agriculture

The table shown below provides some 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. Exit

Land and Crop Management

Adjusting the methods for managing land and growing crops.

Fertilizing crops with the appropriate amount of nitrogen required for optimal crop production, since over-application of nitrogen can lead to higher N₂O emissions without enhancing crop production.

Draining water from wetland rice soils during the growing season to reduce CH₄ emissions.

Livestock Management

Adjusting feeding practices and other management methods to reduce the amount of CH ₄ resulting from enteric fermentation.

Improving pasture quality to increase animal productivity, which can reduce the amount of CH₄ emitted per unit of animal product. Also, increased productivity in livestock can be introduced through improved breeding practices.

Manure Management

Controlling the way in which manure decomposes to reduce N₂O and CH₄ emissions.

Capturing CH₄ from manure decomposition to produce renewable energy.

Handling manure as a solid or depositing it on pasture rather than storing it in a liquid-based system such as a lagoon. This would likely reduce CH₄ emissions but may increase N₂O emissions.

Storing manure in anaerobic containment areas to maximize CH₄ production and then capturing the CH₄ to use as an energy substitute for fossil fuels.

For more information, see EPA's AgSTAR Program, a voluntary outreach and education program that promotes recovery and use of methane from animal manure.

Land Use, Land-Use Change, and Forestry Sector Emissions and Sequestration

Plants absorb carbon dioxide (CO₂) from the atmosphere as they grow, and they store some of this carbon throughout their lifetime. Soils 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 and soils is called biological carbon sequestration. Because biological sequestration takes CO ₂ out of the atmosphere, it is also called a carbon "sink."

Emissions or sequestration of CO ₂, CH ₄ and N ₂ O can occur from management of lands in their current use or as lands are converted to other 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, since 1990, Land Use, Land-Use Change, and Forestry (LULUCF) activities have resulted in more removal of CO ₂ 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 CO ₂ over this time-period. 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 f rom c arbon s tocks are presented under the Land Use, Land-Use Change, and Forestry sector in the Inventory. However, e missions from methane (CH₄) and nitrous oxide (N₂O) are presented in the Energy sector.

Emissions and Trends

In 2016, the net CO ₂ removed from the atmosphere from the LULUCF sector offset about 11 percent of total U.S. greenhouse gas emissions. Between 1990 and 2016, total carbon sequestration in the LULUCF sector decreased by approximately 9 percent, primarily due to a decrease in the rate of net carbon accumulation in forests and cropland, as well as an increase in CO ₂ emissions from urbanization.

Reducing Emissions and Enhancing Sinks from Land Use, Land-Use Change, and Forestry

In 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. Exit

Change in Uses of Land

Increasing carbon storage by using land differently or maintaining carbon storage by avoiding land degradation.

Minimizing the conversion of forest land to other land uses, such as settlements, croplands, or grasslands.

Changes in Land Management Practices

Improving management practices on existing land-use types.

Utilizing reduced tillage practices on cropland and improved grazing management practices on grassland.

Planting after natural or human-induced forest disturbances to accelerate vegetation growth and minimize soil carbon losses.

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Sources of Greenhouse Gas Emissions | US EPA

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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. The largest source of greenhouse gas emissions from human activities in the United States is from burning fossil fuels for electricity, heat, and transportation.

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Some cars have gasoline alternatives, such as ethanol, which when used can reduce emissions by as much as 59%. Ethanol is also a renewable fuel, as it is an alcohol based blend, gotten from distilling crops such as corn and barley.

About:

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Driving Ethanol :: Is it Good for the Environment?

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DrivingEthanol.org is a website focused on demonstrating the benefits of ethanol. Learn about where you can find ethanol, how it's made, its positive impact on the environment and our economy, and what needs to be done to further expand the benefits of homegrown ethanol.

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Carbon dioxide isn't completely emitted by us. Though it is a minor percentage, carbon is emitted by volcanic eruptions and respiration. However, more and more occurrences such as volcanic eruptions may happen, which would be caused by human activity.

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Climate Change: Vital Signs of the Planet

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The Greenhouse Effect

Increasing Greenhouses Gases Are Warming the Planet

Scientists attribute the global warming trend observed since the mid-20 th century to the human expansion of the "greenhouse effect" ¹ - warming that results when the atmosphere traps heat radiating from Earth toward space.

Life on Earth depends on energy coming from the Sun. About half the light energy reaching Earth's atmosphere passes through the air and clouds to the surface, where it is absorbed and radiated in the form of infrared heat. About 90% of this heat is then absorbed by greenhouse gases and re-radiated, slowing heat loss to space.

Gases that Contribute

The Role of Humans

Human Activity Is the Cause of Increased Greenhouse Gas Concentrations

Over the last century, burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO ₂). This increase happens because the coal or oil burning process combines carbon with oxygen in the air to make CO ₂. To a lesser extent, clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases.

How do we know what greenhouse gas and temperature levels were in the distant past?

Ice cores are scientists' best source for historical climate data. Other tools for learning about Earth's ancient atmosphere include growth rings in trees, which keep a rough record of each growing season's temperature, moisture and cloudiness going back about 2,000 years. Corals also form growth rings that provide information about temperature and nutrients in the tropical ocean. Other proxies, such as benthic cores, extend our knowledge of past climate back about a billion years.

detailed answer

The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750 ². This increase is due to human activities, because scientists can see a distinctive isotopic fingerprint in the atmosphere.

In its Sixth Assessment Report, the Intergovernmental Panel on Climate Change, composed of scientific experts from countries all over the world, concluded thatit is unequivocal that the increase of CO ₂, methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere and biosphere.

"Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact."

- Intergovernmental Panel on Climate Change

The panel's AR6 Working Group I (WGI) Summary for Policymakers report is online at https://www.ipcc.ch/report/ar6/wg1/.

Is the Sun to Blame?

Evidence Shows That Current Global Warming Cannot Be Explained by Solar Irradiance

Scientists use a metric called Total Solar Irradiance (TSI) to measure the changes in energy the Earth receives from the Sun. TSI incorporates the 11-year solar cycle and solar flares/storms from the Sun's surface.

Studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity coupled with increased volcanic activity helped trigger the Little Ice Age.

The above graph compares global surface temperature changes (red line) and the Sun's energy that Earth receives (yellow line) in watts (units of energy) per square meter since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious.

The amount of solar energy that Earth receives has followed the Sun's natural 11-year cycle of small ups and downs with no net increase since 1880. Over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-century. Credit: NASA/JPL-Caltech

But several lines of evidence show that current global warming cannot be explained by changes in energy from the Sun:

Since 1750, the average amount of energy from the Sun either remained constant or decreased slightly³.

If a more active Sun caused the warming, scientists would expect warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere and a warming at the surface and lower parts of the atmosphere. That's because greenhouse gases are slowing heat loss from the lower atmosphere.

Climate models that include solar irradiance changes can't reproduce the observed temperature trend over the past century or more without including a rise in greenhouse gases.
References
References

1. IPCC 6 th Assessment Report, WG1, Summary for Policy Makers, Sections A, " The Current State of the Climate "

IPCC 6 th Assessment Report, WG1, Technical Summary, Sections TS.1.2, TS.2.1 and TS.3.1

2. P. Friedlingstein, et al., 2022: "Global Carbon Budget 2022", Earth System Science Data ( 11 Nov 2022): 4811-4900. https://doi.org/10.5194/essd-14-4811-2022

3. IPCC 6 th Assessment Report, WG1, Chapter 2, Section 2.2.1, " Solar and Orbital Forcing"

IPCC 6 th Assessment Report, WG1, Chapter 7, Sections 7.3.4.4, 7.3.5.2, Figure 7.6, " Solar"

M. Lockwood and W.T. Ball, Placing limits on long-term variations in quiet-Sun irradiance and their contribution to total solar irradiance and solar radiative forcing of climate," Proceedings of the Royal Society A, 476, issue 2228 (24 June 2020): https://doi 10.1098/rspa.2020.0077

Header image credit: Pixabay/stevepb

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Vital Signs of the Planet: Global Climate Change and Global Warming. What is the "greenhouse effect"? What is causing it? Are humans to blame? What does solar irradiance have to do with it? Answers here.