Us Pollution Output: A Comprehensive Overview

The United States is one of the world's largest emitters of pollution, with the country's greenhouse gas emissions totalling 6.3 billion metric tons in 2021. Carbon dioxide is the most common greenhouse gas, with human activities such as burning fossil fuels for electricity, heat, and transportation being the primary source of emissions. In 2019, the US emitted 5,130 million metric tons of energy-related carbon dioxide, contributing significantly to global emissions. While there have been improvements in air quality since 1980, pollution remains a pressing issue, with approximately 140 million people in the US living in counties with pollution levels above the primary NAAQS as of 2023.

Greenhouse gas emissions

The US emitted 5,130 million metric tons of energy-related carbon dioxide in 2019, while global emissions of energy-related carbon dioxide totalled 33,621.5 million metric tons. In 2020, the US produced 5.2 billion metric tons of carbon dioxide equivalent in greenhouse gas emissions, the second-largest in the world after China. The US has emitted a quarter of the world's greenhouse gases, more than any other country. Annual emissions are over 15 tons per person, and the richest decile in the US emits over 55 tons of CO2 per capita each year.

The top sources of greenhouse gas emissions in the US are the burning of fossil fuels for electricity and transportation. In 2020, the breakdown of greenhouse gas emissions by the economic sector in the US was as follows: transportation (27%), electricity (25%), industry (24%), commercial and residential (13%), and agriculture (11%). The transportation sector includes all forms of transportation, such as cars, trucks, buses, airplanes, and ships, which are mostly powered by fossil fuels. Passenger cars are responsible for the largest share of transportation sector greenhouse gas emissions in the US.

The US government has held shifting attitudes toward addressing greenhouse gas emissions. While the George W. Bush administration did not sign the Kyoto Protocol, the Obama administration entered the Paris Agreement, from which the Trump administration withdrew. In 2021, the Biden administration committed to reducing emissions to half of 2005 levels by 2030. In 2022, President Biden signed the Inflation Reduction Act, which is expected to provide around $375 billion over 10 years to fight climate change.

Carbon dioxide emissions

Carbon dioxide is the most common greenhouse gas produced by human activities. The burning of fossil fuels for electricity, heat, and transportation is the primary source of carbon dioxide emissions in the United States. From 1990 to 2022, greenhouse gas emissions per dollar of goods and services produced by the US economy (the gross domestic product or GDP) declined by 55%. This decrease may be due to increased energy efficiency and structural economic changes.

The transportation sector is the largest contributor to direct greenhouse gas emissions and the second-largest contributor when indirect emissions from electricity end-use are considered. Over 94% of the fuel used for transportation is petroleum-based, including gasoline and diesel, which results in direct emissions. The commercial and residential sectors also contribute significantly to greenhouse gas emissions, particularly when indirect emissions from electricity end-use are included. Buildings in the United States consume 75% of the electricity generated, primarily for heating, ventilation, air conditioning, lighting, and appliances.

In 2022, the United States emitted 5,130 million metric tons of energy-related carbon dioxide, while global energy-related carbon dioxide emissions totaled 33,621.5 million metric tons. The US greenhouse gas emissions increased by 0.2% in 2022 compared to 2021 levels. However, in 2023, US energy-related carbon dioxide emissions decreased slightly compared to 2022, primarily due to reduced coal-fired electricity generation and increased use of natural gas and solar power. The industrial sector emissions remained relatively unchanged, with a slight increase in natural gas emissions due to increased industrial production.

To address carbon dioxide emissions, the United States employs carbon sequestration, which involves capturing and storing atmospheric carbon dioxide. The USGS assesses geologic and biologic carbon sequestration methods, with an estimated mean storage potential of 3,000 metric gigatons of carbon dioxide. Additionally, land use, land-use change, and forestry practices act as carbon sinks, offsetting 13% of greenhouse gas emissions.

Fossil fuels and transport

Fossil fuels, such as coal, natural gas, and petroleum, are a significant source of pollution in the United States. In 2022, burning fossil fuels accounted for 74% of total greenhouse gas emissions in the country. The transportation sector is the largest contributor to these emissions, with cars, trucks, ships, trains, and planes burning fossil fuels for fuel. Over 94% of the fuel used for transportation is petroleum-based, and the sector is responsible for about 28% of total US greenhouse gas emissions.

The US Environmental Protection Agency (EPA) has implemented various measures to reduce greenhouse gas emissions from transportation. These include the Renewable Fuel Standard program, which aims to reduce reliance on imported oil and expand the use of renewable fuels produced from plants, crops, and biomass. The EPA has also developed international carbon dioxide emissions standards for aircraft in collaboration with the Federal Aviation Agency and the United Nations' International Civil Aviation Organization (ICAO). Additionally, the EPA provides resources like the Green Vehicle Guide and the SmartWay light-duty program to help consumers choose more fuel-efficient and environmentally friendly vehicles.

Despite these efforts, transportation emissions in the US have been on the rise. In 2022, vehicles on land, sea, and air in the US emitted almost two billion metric tons of carbon dioxide equivalents into the atmosphere. This accounts for more than a quarter of domestic greenhouse gas emissions and nearly a quarter of global transportation emissions, making the US the world's biggest polluter in terms of transportation-related activities.

Road travel is the largest source of transportation emissions in the US. In 2022, combustion-engine light-duty trucks and heavy-duty trucks were the highest emitting vehicles, with emissions of roughly 645 and 400 million metric tons of carbon dioxide equivalents, respectively. Passenger cars generated about 360 million metric tons, and while they were once the highest-emitting vehicles, improved efficiency and stricter emissions standards have reduced their environmental impact.

Commercial and residential emissions

Direct emissions in the residential and commercial sectors are produced through the combustion of natural gas and petroleum products for heating and cooking, which emit carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Natural gas consumption made up 78% of direct fossil fuel CO2 emissions in this sector in 2022. Other sources of direct emissions include waste and wastewater management, and leaks from refrigerants in homes and businesses.

Indirect emissions in the commercial and residential sectors are produced by burning fossil fuels at power plants to generate electricity, which is then used for lighting, appliances, and plug loads in homes and businesses. Buildings use 75% of the electricity generated in the US, and electricity consumption is a significant contributor to indirect emissions in this sector.

It is important to note that the commercial and residential sector emissions do not include emissions/sinks from the production of construction materials or emissions from land use changes. These emissions would be reflected in other sectors. Additionally, energy use in these sectors may also include energy used for equipment, exterior lighting, or construction, which can impact overall emissions.

From 1990 to 2022, US greenhouse gas emissions per dollar of goods and services produced by the US economy (GDP) declined by 55%. This decrease may be due to increased energy efficiency and structural changes in the economy. However, it is important to consider that emissions can fluctuate from year to year due to various factors such as economic activity, population changes, consumption patterns, energy prices, land use, and technology. For example, in 2023, emissions in the residential and commercial sectors decreased due to milder weather, which reduced the demand for space heating and cooling in buildings.

Agriculture and livestock

Livestock are responsible for a significant amount of methane emissions, which have a much greater planet-warming power than carbon dioxide. This is due to enteric fermentation, a normal part of the digestive process in ruminant animals like cows, sheep, and goats, where gut microbes decompose and ferment fibrous foods, producing methane. Livestock manure is also a major source of air pollution, as it emits ammonia, which combines with other air pollutants to create solid particles that can cause heart and lung diseases. In the United States, farms are responsible for more than 90% of airborne ammonia pollution, mostly from fertilizers and livestock manure.

Agricultural activities also contribute to water pollution. Livestock manure, which often contains antibiotics and hormones, can contaminate water sources, along with fertilizers and pesticides. Extensive plowing and other practices have also led to soil erosion, reducing its ability to absorb nutrients and allowing more chemicals to be washed away into waterways. Climate change further exacerbates these issues, as heavy rains can increase agricultural runoff, carrying pollutants into oceans, lakes, and streams, and leading to depleted oxygen levels, a phenomenon known as hypoxia, which can kill fish and shellfish.

The high demand for meat, dairy, and eggs in the United States has intensified the environmental impact of the agriculture and livestock industry. As disposable income has risen, meat consumption has increased, with Americans consuming an estimated 225 pounds of red meat and poultry per person annually in 2022. This demand has led to the intensive farming of billions of animals each year in concentrated animal feeding operations (CAFOs), which has significant environmental costs.

To mitigate the pollution generated by the agriculture and livestock industry, several solutions have been proposed, including adapting to a plant-based food system and implementing agroecology practices that work with nature to protect natural resources.

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