#human #activities, #energy, #trucks, #cars, #fossil #fuels, #ghg, #ghgs
Sources of Greenhouse Gas Emissions
* Land Use, Land-Use Change, and Forestry in the United States is a net sink and offsets approximately 11.8 percent of these greenhouse gas emissions, not included in total above. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 2015.
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:
- Electricity production (29 percent of 2015 greenhouse gas emissions) – Electricity production generates the largest share of greenhouse gas emissions. Approximately 67 percent of our electricity comes from burning fossil fuels, mostly coal and natural gas. 2
- Transportation (27 percent of 2015 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. 3
- Industry (21 percent of 2015 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.
- Commercial and Residential (12 percent of 2015 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.
- Agriculture (9 percent of 2015 greenhouse gas emissions) – Greenhouse gas emissions from agriculture come from livestock such as cows, agricultural soils, and rice production.
- Land Use and Forestry (offset of 11.8 percent of 2015 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, U.S. greenhouse gas emissions have increased by about 4 percent. From year to year, emissions can rise and fall due to changes in the economy, the price of fuel, and other factors. In 2015, U.S. greenhouse gas emissions decreased compared to 2014 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; and a slight decrease in electricity demand.
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 U.S. Energy Information Administration (2016). Electricity Explained – Basics .
3 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.
Electricity Sector Emissions
* Land Use, Land-Use Change, and Forestry in the United States is a net sink and offsets approximately 11.8 percent of these greenhouse gas emissions, not included in total above. All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 2015 .
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 (N2 O) 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 generally more carbon intensive than burning natural gas or petroleum for electricity. Although coal accounted for about 70 percent of CO2 emissions from the sector, it represented only about 34 percent of the electricity generated in the United States in 2015. Another 32 percent of electricity generated in 2015 was generated using natural gas, an increase relative to 2014. Petroleum accounted for less than 1 percent of electricity generation in 2015. The remaining generation in 2015 came from non-fossil fuel sources including nuclear (about 20 percent) and renewable sources (about 13 percent), which include hydroelectricity, biomass, wind, and solar. 1 These other sources usually release fewer greenhouse gas emissions than fossil fuel combustion, if any emissions at all.
Emissions and Trends
In 2015, the electricity sector was the largest source of U.S. greenhouse gas emissions, accounting for about 29 percent of the U.S. total. Greenhouse gas emissions from electricity have increased by about 4 percent since 1990 as electricity demand has grown and fossil fuels have remained the dominant source for generation.
Greenhouse Gas Emissions by Electricity End-Use
Larger image to save or print. Electricity is consumed by other sectors — in 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
Example Reduction Opportunities for the Electricity Sector
How Emissions Are Reduced