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Visualizing the Flow of Energy-Related CO2 Emissions in the U.S.

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The following content is sponsored by the National Public Utilities Council

The Flow of Energy-Related CO2 Emissions in the U.S.

In 2021, U.S. carbon dioxide emissions from the generation and consumption of energy reached 4.9 billion tonnes. Fossil fuels including petroleum, natural gas, and coal made up 100% of these emissions.

To better understand how various energy sources and their end-uses contribute to carbon emissions, this graphic sponsored by the National Public Utilities Council visualizes the flow of energy-related CO2 emissions in the United States.

What Are Energy-Related CO2 Emissions?

Energy-related CO2 emissions refer to the release of carbon dioxide as a result of the combustion of fuels to produce energy. They arise through the direct use of fossil fuels for transport, heating, or industrial needs, as well as the use of fossil fuels for electricity generation.

In addition to the emissions that arise from the generation and consumption of energy, there are several other ways CO2 emissions can arise. To provide some context, they can result as a byproduct of industrial chemical reactions, deforestation, and agricultural activities.

As the largest contributor to carbon emissions, however, energy-related CO2 emissions account for approximately 85% of all emissions in the United States, which we will now explore in further detail.

U.S. Energy-Related CO2 Emissions in 2021

Followed by a pandemic-driven decline in 2020, energy-related CO2 emissions in the U.S. increased by 325 million tonnes in 2021, marking the largest-ever annual increase. Clean energy sources, namely solar, wind, nuclear, biomass and hydropower, accounted for 0% of these emissions.

Energy SourceCO2 emissions in million tonnes, 2021% of total energy-related emissions
Petroleum2,22345.7%
Natural Gas1,63733.7%
Coal1,00320.6%
Solar, Wind, Nuclear, Hydro, and Biomass00%
Total4,863100%

When we follow the CO2 emissions from the above fossil fuels to their end uses, transportation and electricity generation stand out as the biggest contributors.

In 2021, these two sectors accounted for more than 68% of all energy-related emissions in the country, roughly emitting 3.3 billion tonnes of CO2.

End-Uses CO2 emissions in million tonnes, 2021% of total energy-related emissions
Transportation1,80137.0%
Electricity Generation1,53731.6%
Industrial Uses96519.8%
Residential Uses3216.6%
Commercial Uses2394.9%
Total4,863100%

When it comes to transportation, petroleum accounted for 97% of emissions, largely due to motor gasoline and diesel consumption. On the other hand, coal and natural gas made up 99% of CO2 emissions related to electricity generation.

Due to its high carbon intensity, coal’s contribution to power sector emissions is of particular interest. As the share of coal rose from 20% to 23% in the U.S. electricity mix in 2021, electricity emissions from coal also increased for the first time since 2014.

Naturally, this shift raised the overall energy-related CO2 emissions in 2021. It also caused a 4% hike in the carbon intensity of the country’s electricity, hinting at the urgent need for a shift away from coal.

The Path to Decarbonization: Lowering Emissions

The impact of climate change has become increasingly clear in recent years. To avoid its worst impacts, it’s essential to achieve decarbonization across all sectors, which requires significant reductions in energy-related carbon emissions.

One of the most critical sectors for emissions reductions is transportation, which accounts for nearly 40% of all energy-related CO2 emissions. The good news is that there is enormous potential to reduce these emissions through the use of electric vehicles and the decarbonization of the electricity used to charge them.

To decarbonize the power sector, the U.S. must transition away from fossil fuels and towards clean energy sources such as wind, solar, and nuclear power. Once achieved, decarbonized electricity also has the power to reduce emissions from all other sectors that use electricity, including industrial, residential and commercial activities.

By taking bold action toward these objectives, the U.S. can accelerate the transition to a clean energy future within its borders and beyond.

Click here to learn more about how electric utilities and the power sector can lead on the path toward decarbonization.

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Emissions

The Most Polluted Cities in the U.S.

Here are the most polluted cities in the U.S. according to data from the American Lung Association’s 2024 State of the Air Report.

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Teaser image for an infographic showing the most polluted cities in the U.S. according to the American Lung Association's 2024 State of the Air report.

The Most Polluted U.S. Cities in 2024

According to the World Health Organization, air pollution is responsible for 7 million deaths annually, and could cost the global economy between $18–25 trillion by 2060 in annual welfare costs, or roughly 4–6% of world GDP.

And with predictions that 7 in 10 people will make their homes in urban centers by mid-century, cities are fast becoming one of the frontlines in the global effort to clear the air.

In this visualization, we use 2024 data from the State of the Air report from the American Lung Association to show the most polluted cities in the United States.

What is Air Pollution?

Air pollution is a complex mixture of gases, particles, and liquid droplets and can have a variety of sources, including wildfires and cookstoves in rural areas, and road dust and diesel exhaust in cities.

There are a few kinds of air pollution that are especially bad for human health, including ozone and carbon monoxide, but here we’re concerned with fine particulate matter that is smaller than 2.5 microns, or PM2.5 for short.

The reason for the focus is because at that small size, particulate matter can penetrate the bloodstream and cause all manner of havoc, including cardiovascular disease, lung cancer, and chronic pulmonary disease.

The American Lung Association has set an annual average guideline of 9 µg/m³ for PM2.5, however, the World Health Organization has set a much more stringent limit of 5 µg/m³.

The 21 Worst Polluted Cities in the U.S.

Here are the top 21 most polluted cities in the U.S., according to their annual average PM2.5 concentrations:

RankCity, StateAnnual average concentration, 2020-2022 (µg/m3)
1Bakersfield, CA18.8
2Visalia, CA18.4
3Fresno, CA17.5
4Eugene, OR14.7
5Bay Area, CA14.3
6Los Angeles, CA14.0
7Sacramento, CA13.8
8Medford, OR13.5
9Phoenix, AZ12.4
10Fairbanks, AK12.2
11Indianapolis, IN11.9
12Yakima, WA11.8
13Detroit, MI11.7
14Chico, CA11.6
14Spokane, WA11.6
15Houston, TX11.4
16El Centro, CA11.1
17Reno, NV11.0
18Pittsburgh, PA10.9
19Kansas City, KS10.8
19Las Vegas, NV10.8

Note: The American Lung Association uses Core Based Statistical Areas in its city and county rankings, which have been shortened here to the area’s principal city, or metro area in the case of the Bay Area, CA.

Six of the top seven cities are in California, and four in the state’s Central Valley, a 450-mile flat valley that runs parallel to the Pacific coast, and bordered by the Coast and Sierra Nevada mountain ranges. As a result, when pollution from the big population centers on the coast is carried inland by the wind—cities #5 and #6 on the list—it tends to get trapped in the valley.

Bakersfield (#1), Visalia (#2), and Fresno (#3) are located at the drier and hotter southern end of the valley, which is worse for air quality. The top three local sources of PM2.5 emissions in 2023 were farms (20%), forest management / agricultural waste burning (20%), and road dust (14%).

Benefit to Economy

While the health impacts are generally well understood, less well known are the economic impacts.

Low air quality negatively affects worker productivity, increases absenteeism, and adds both direct and indirect health care costs. But the flip side of that equation is that improving air quality has measurable impacts to the wider economy. The EPA published a study that calculated the economic benefits of each metric ton of particulate matter that didn’t end up in the atmosphere, broken down by sector, including utilities.

SectorBenefits per metric ton
Residential Woodstoves$429,220
Refineries$333,938
Industrial Boilers$174,229
Oil and Natural Gas Transmission$125,227
Electricity Generating Units$124,319
Oil and Natural Gas$88,838

At the same time, the EPA recently updated a cost-benefit analysis of the Clean Air Act, the main piece of federal legislation governing air quality, and found that between 1990 and 2020 it cost the economy roughly $65 billion, but also provided $2 trillion in benefits.

Benefit to Business

But that’s at the macroeconomic level, so what about for individual businesses?

For one, employees like to breathe clean air and will choose to work somewhere else, given a choice. A 2022 Deloitte case study revealed that nearly 70% of highly-skilled workers said air quality was a significant factor in choosing which city to live and work in.

At the same time, air quality can impact employer-sponsored health care premiums, by reducing the overall health of the risk pool. And since insurance premiums averaged $7,590 per year in 2022 for a single employee, and rose to $21,931 for a family, that can add up fast.

Consumers are also putting their purchase decisions through a green lens, while ESG, triple-bottom-line, and impact investing are putting the environment front and center for many investors.

And if the carrot isn’t enough for some businesses, there is the stick. The EPA recently gave vehicle engine manufacturer Cummins nearly two billion reasons to help improve air quality, in a settlement the agency is calling “the largest civil penalty in the history of the Clean Air Act and the second largest environmental penalty ever.”

Learn how the National Public Utilities Council is working toward the future of sustainable electricity.

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Emissions

Visualized: Global CO2 Emissions Through Time (1950–2022)

In this streamgraph, we break down global CO2 emissions between 1950 and 2022 using data from Berkeley Earth and Global Carbon Project.

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Preview image of a streamgraph showing global CO2 emissions between 1950-2022, broken down by region.

Visualized: Global CO2 Emissions Through Time (1950-2022)

Global CO2 emissions have grown six-fold since 1950.

But which countries have contributed the most to this growth?

In this streamgraph, created in partnership with the National Public Utilities Council, we answer that question using regional emissions data from Berkeley Earth and Global Carbon Project

Global CO2 Emissions: The Last 70 Years in Review

In the 1950s, the United States and the countries that later formed the European Union (EU) were the biggest emitters in the world, responsible for over 70% of total annual emissions.

However, this trend swiftly changed as other nations entered the fray.

For instance, China’s economic surge in the 1970s, particularly with the advent of Deng Xiaoping’s new economic strategy in 1978, triggered a notable uptick in the country’s CO2 output. From 1950 to 2000, China witnessed a surge of over 4,500% in emissions, reaching an annual 3.6 billion tonnes by 2000.

Similarly, India, Japan, and the broader Asian region, all experienced emission growth exceeding 1,000% between 1950 and 2000.

Metric tons of carbon dioxide (tCO2)195020002022Change 1950–2000Change 2000–2022
China0.1B3.6B11.4B4,529%213%
Asia (excl. China, Japan, and India)0.2B3.2B6.2B1,973%95%
United States of America2.5B6.0B5.1B136%-16%
European Union1.8B4.2B3.1B134%-26%
Rest of World0.4B2.5B2.9B465%16%
India0.1B1.0B2.8B1,500%189%
Russia0.4B1.5B1.7B256%12%
Africa0.1B0.9B1.4B876%52%
Japan0.1B1.3B1.1B1,132%-17%
South America0.1B0.8B1.1B621%34%
Canada0.2B0.6B0.6B268%-3%

Data note: 1950 was used as a beginning point for the graph due to the lack of available data for many countries prior to that year. 

As illustrated in the table above, the growth in global carbon emissions has slowed since 2000.

With that said, global emissions have still risen from 25 billion tonnes in 2000 to 37 billion in 2022, yet another all-time high. Today, over 40% of emissions come from the United States and China, underscoring their pivotal roles in shaping the global emissions landscape.

Where Are We Headed From Here?

The United Nations’ recent Emissions Gap report highlights a concerning reality: the ongoing rate of emissions combined with existing policies steers humanity towards a world that is 3°C warmer than pre-industrial levels. This contrasts starkly with the goals of 1.5–2°C agreed to in 2015.

The Intergovernmental Panel on Climate Change projects that such a degree of warming will bring catastrophic repercussions, from severe changes in weather patterns to rising sea levels, widespread extinctions, and critical disruptions to global food and water systems.

This underscores the critical need for swift, concerted action to curb emissions and mitigate the impending environmental challenges that are potentially before us.

Learn more about how electric utilities and the power sector can lead on the path toward decarbonization here.

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