Sources of Greenhouse Gas Emissions
Electricity Sector Emissions
Total U.S. Greenhouse Gas Emissions by Economic Sector in 2011
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 Electricity Sector by Fuel Source
Coal combustion is generally more carbon intensive than burning natural gas or petroleum for electricity. Although coal accounts for about 80% of CO2 emissions from the sector, it represents about 42% of the electricity generated in the United States. About 25% of electricity generated in 2011 was generated using natural gas, and this percentage has grown in recent years. Petroleum accounts for less than 1% of electricity generation. The remaining generation comes from nuclear (about 19%) and renewable sources (about 13%), which includes 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 2011, the electricity sector was the largest source of U.S. greenhouse gas emissions, accounting for about 33% of the U.S. total. Greenhouse gas emissions from electricity have increased by about 18% since 1990 as electricity demand has grown and fossil fuels have remained the dominant source for generation.
To learn about projected greenhouse gas emissions to 2020, visit the U.S. Climate Action Report 2010 (PDF) (193 pp, 3.1MB)
Greenhouse Gas Emissions from Electricity
Total U.S. Greenhouse Gas Emissions by Sector with Electricity Distributed
Greenhouse Gas Emissions by Electricity End-Use
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 4 of the Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change .
|Type||How Emissions are Reduced||Examples|
|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.||
|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.||In 2010, Americans using ENERGY STAR® products and retrofits saved the energy equivalent of approximately 45 power plants--preventing 195 million metric tons of CO2 emissions, and saving more than $20 billion in their energy bills. Learn more about opportunities to improve efficiency in the Industry sector and the Commercial and Residential sector.|
|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 CO2 as a by-product of fossil fuel combustion before it enters the atmosphere and then transferring the CO2 to a long-term storage area, such as an underground geologic formation.||Capturing CO2 from the stacks of a coal-fired power plant, and then transferring the CO2 via pipeline to a nearby abandoned oil field where the CO2 is injected underground. Learn more about CCS.|