In order to avert and mitigate the most damaging effects of the climate crisis, countries must take action to reduce their greenhouse gas emissions. Although estimated to be 17 percent lower today than in 2005, U.S. emissions remain a major contributor to global greenhouse gas emissions, and therefore, to the climate crisis.
What Is the Biggest Contributor of Greenhouse Gas Emissions in the U.S.?
For many years the most polluting industry in the U.S. was the electrical power sector, but this changed in 2016 thanks to surging transportation industry emissions. Together with the transportation and energy production industries, animal agriculture and forestry also make major contributions to greenhouse gas emissions.
Fossil fuels such as gasoline and diesel are the primary fuel sources of the transportation industry. Burning fossil fuels results in the production of carbon dioxide, along with methane, nitrous oxide and hydrofluorocarbons. The greenhouse gas emissions of the transportation industry account for around 28 percent of all emissions in the U.S., making it the largest contributor to U.S. greenhouse gas emissions. In 2021 this equated to 1.8 billion tons of carbon dioxide being released into the atmosphere.
Around three-quarters of the transportation industry’s emissions globally come from road travel, meaning that our everyday transportation choices continue to have a huge impact on greenhouse gas emissions. The aviation industry also plays a significant role, contributing over 11 percent of the transportation industry’s overall emissions.
Electrical power production was responsible for 25 percent of U.S. greenhouse gas emissions in 2020, making it the second-largest source of greenhouse gas emissions in the U.S. The combustion of coal to produce electricity is the industry’s largest source of these emissions, with burning of other fossil fuels close behind. Producing electricity from coal and other fossil fuels results in the release of large quantities of carbon dioxide, as well as smaller quantities of methane and nitrous oxide. The greenhouse gases emitted through electricity production can be minimized by switching to wind, solar or other methods of renewable energy production. In recent years increasing amounts of energy have been produced through renewable sources, reaching 19.8 percent of utility-scale electricity generation in 2021 (and 12.4 percent of all energy use). Since 2005 the greenhouse gas emissions of the U.S. electrical power sector have decreased by 36 percent.
The industrial sector isn’t far behind energy generation in terms of its greenhouse gas emissions, responsible for 24 percent of U.S. emissions in 2020. Industrial production of greenhouse gases includes emissions released during the production of chemicals, refining of metals, iron and steel production and other industrial processes. The industrial sector is also responsible for greenhouse gas emissions due to its large energy consumption. In order to reduce its environmental impact, the industrial sector will need to commit to using more renewable sources of energy, and investment will need to be made into researching lower-emission manufacturing methods.
Commercial and Residential
Businesses and homes were responsible for 13 percent of U.S. greenhouse gas emissions in 2020, mostly due to heating, cooking and waste disposal. When production of electricity from homes and businesses is included in these statistics, the sector accounts for 30 percent of emissions. Reducing the greenhouse gas emissions from homes and businesses presents challenges, but their environmental impact can be decreased by reducing energy usage as much as possible, for example, through changes in construction that make buildings easier to keep at a constant temperature, as well as by replacing electricity that has come from burning fossil fuels with power generated from renewable energy sources
In 2020 the agriculture industry was responsible for 11 percent of U.S. greenhouse gas emissions, much of which comes from the animals themselves, particularly cattle. When ruminant animals such as cows and sheep digest their food, they release methane and nitrous oxide — two highly potent greenhouse gases — into the atmosphere. The vast numbers of animals raised by the animal agriculture industry each year, and therefore emitting these gases, make the industry a key contributor to U.S. greenhouse gas emissions. The industry also emits greenhouse gases through the production of huge quantities of animal feed, the manure it produces and synthetic fertilizer use.
In addition to direct emissions, the agriculture industry contributes to climate change as a result of land cleared to make space for cattle and feed production. Once cleared, this land is no longer able to absorb carbon dioxide from the atmosphere, which comes at a cost to the planet, often described as the “carbon opportunity cost.” Clearing tropical forests for animal feed production and grazing on a global scale poses a grave threat to the future of Earth’s climate.
Land Use and Forestry
The way in which an area of land is used has the potential to contribute to or reduce net greenhouse gas emissions. Forests, for example, can act as a carbon reserve, absorbing more carbon dioxide than they emit. Through activities such as deforestation, however, emissions are released, and these natural carbon reserves are destroyed — meaning that the carbon dioxide they previously stored is released back into the atmosphere
How Much Does the U.S. Contribute to Global Greenhouse Gases?
The U.S. significantly contributes to global greenhouse gas emissions. Although it only accounts for 5 percent of the population, the country’s carbon emissions equate to 30 percent of global carbon emissions.
U.S. Greenhouse Gas Emissions by State
The state of Texas makes the largest contribution to U.S. greenhouse gas emissions, releasing 13 percent of the country’s carbon dioxide. Because of the state’s large population, however, when U.S. states’ emissions are compared on a per capita basis, Texas ranks around ninth. Per person, Wyoming produces the highest volume of carbon dioxide, as Wyoming is where 40 percent of U.S. coal production takes place. The state of Vermont produces the lowest quantity of carbon dioxide per capita.
U.S. Greenhouse Gas Emissions by Sector
The largest producers of greenhouse gas emissions in the U.S. are the transportation and electrical energy production industries. The transportation industry is responsible for 28 percent of emissions and the electrical energy sector is responsible for 25 percent.
A less commonly known but still significant producer of greenhouse gases is the agriculture industry. The agriculture industry contributes to emissions through the large number of livestock it raises and kills each year, and the land management practices that this entails. In 2020 it contributed 11.2 percent of U.S. greenhouse gas emissions
U.S. Greenhouse Gas Emissions by Year
Like the rest of the world, the U.S. produced significantly fewer greenhouse gas emissions in 2020 than it had in previous years due to the COVID-19 pandemic. With a significant reduction in travel, which makes the largest contribution to greenhouse gas emissions, overall levels of emissions fell by 10 percent.
In 2021, however, emissions began to rise again, increasing by 6.2 percent and approaching pre-pandemic levels. Current predictions estimate that U.S. greenhouse gas emissions will increase by a further 1.5 percent, but then begin to fall again in 2023.
U.S. Greenhouse Gas Emissions by Gas
When fossil fuels, waste products or plants are burned, carbon dioxide is released into the atmosphere. Carbon dioxide is released in far higher volumes than any other greenhouse gas, and this scale means that among greenhouse gases, carbon dioxide creates the greatest warming potential. In 2020, human-caused greenhouse gas emissions were 79 percent carbon dioxide. The remaining emissions were composed of methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride and nitrogen trifluoride.
Methane production in the U.S. is mostly due to the oil and gas industry and animal agriculture. Methane gas has 80 times the capacity of carbon dioxide to trap heat in the planet’s atmosphere over a 20-year period. Cutting methane emissions would make a significant contribution to decreasing the current rate of global warming. It’s estimated that at least 25 percent of global warming today is related to human-caused methane production.
Although produced in smaller quantities than carbon dioxide or methane, nitrous oxide is a highly dangerous greenhouse gas, possessing 273 times the heat-trapping abilities of carbon dioxide over a 100-year period. Nitrous oxide is mainly emitted through the agriculture industry and other industrial activities, making up 7 percent of U.S. greenhouse gas emissions in 2020.
Hydrofluorocarbons, perfluorocarbons, hexafluoride and nitrogen trifluoride also contribute to the greenhouse effect and were responsible for 3 percent of greenhouse gas emissions from the U.S. in 2020. Although these are again produced in far smaller quantities than carbon dioxide, these gases, known as fluorinated gases, are significantly better at trapping heat than carbon dioxide. This makes them highly potent greenhouse gases with serious potential to impact climate change.
Is the U.S. a Major Emitter of Greenhouse Gases?
On the world stage, the U.S. is a major emitter of greenhouse gases. The U.S. contributed 6 billion metric tons of carbon dioxide-equivalent greenhouse gas emissions in 2020, making it the second-largest producer of greenhouse gases and therefore a serious contributor to global climate change.
What Is the U.S. Doing To Reduce Greenhouse Gas Emissions?
The U.S. is aiming to achieve net zero emissions by the year 2050. Efforts to do this include transitioning to clean energy sources, switching to clean fuels for transportation, reducing energy waste, and investing in methods of removing carbon dioxide from the atmosphere.
What You Can Do
The phenomenal scale of greenhouse gas emissions can make it easy to feel like there’s nothing that we as individuals can do to limit these emissions or have an impact on climate change. Yet there are several small practical steps you can take to help limit greenhouse gas emissions.
The contribution that the transportation industry makes to greenhouse gas emissions provides one opportunity for limiting our individual environmental impacts. By thinking more carefully about how we travel, reducing how much we travel and taking more environmentally friendly modes of transportation when possible, we can limit our household contribution to greenhouse gas production.
As energy production is the next largest source of greenhouse gas emissions in the U.S., reducing the amount of electricity you use on a daily basis helps to contribute to reducing emissions. As well as minimizing your individual energy usage, finding an energy supplier that uses hydropower, solar or wind power to generate its electricity is a great way to limit your contribution to greenhouse gas production.
When we think of reducing our environmental impact or carbon footprint we tend to think more of our energy usage or transportation methods, but dietary change is another effective method of climate action. You can help by replacing some or all of the meat-based products in your diet with plant-based alternatives, and curbing food waste.