United States of America's Sources of N2O Emissions
Key Insights
Agricultural Emissions Dominate
Throughout the decades, agricultural activities have consistently been the largest contributor to N₂O emissions in the USA. The post-World War II industrial boom and subsequent agricultural intensification in the 1980s significantly increased emissions from this sector. The use of synthetic fertilizers and mechanization led to a notable rise in N₂O emissions, reflecting the sector's growing impact on the environment.
Industrial and Energy Shifts
The industrial sector saw a dramatic rise in N₂O emissions during the mid-20th century, peaking in the 1960s and 1970s. This increase was driven by the post-war industrial expansion and the establishment of coal-fired power plants. However, the Clean Air Act Amendments of 1990 marked a turning point, leading to a reduction in emissions as industries adopted cleaner technologies. Meanwhile, energy-related emissions fluctuated, with significant decreases observed in recent decades, partly due to the shift towards renewable energy sources and the impact of the COVID-19 pandemic.
Waste and Other Sources
Emissions from waste and other sources have shown a steady increase over the years, albeit at a smaller scale compared to agriculture and industry. The rise in waste emissions reflects the growing population and urbanization, while emissions from other sources have seen a decline in recent decades, indicating improvements in waste management and environmental policies. These trends highlight the complex interplay of economic growth, policy interventions, and technological advancements in shaping the USA's N₂O emissions profile.
Background
The chart shows a national breakdown by source of the yearly nitrous oxide (N2O) emissions from human activities and processes, expressed as weight in megatonnes (Mt). Human-induced emissions are the main driver of the increasing atmospheric nitrous oxide that is warming our planet. The sources of human nitrous oxide emissions are
- Agriculture
- Energy
- Industry
- Waste
- Other
Agriculture
Emissions related to agriculture are mainly from the use of synthetic fertilizers and manure management.
Synthetic fertilizer, used for agricultural processes, contains a lot of nitrogen. That nitrogen in the soil reacts and causes considerable N2O emissions. The use of excess fertilizer, meaning more fertilizer than the plants can use to grow, causes even higher relative emissions. Applying the right amount of fertilizer at the right time can reduce N2O emissions. There are many technical solutions to reduce emissions while keeping, or even increasing, agricultural yields.
When manure is left on the field or otherwise managed in dry processes, it emits considerable amounts of nitrous oxide. Manure can be managed by wet processes, which reduces nitrous oxide emissions but increases methane emissions. Some technical solutions focus on modifying the animal feed to reduce the nitrogen in the manure, thereby reducing nitrous oxide emissions.
Energy, Industry, Waste, and Other
All non-agricultural categories together have much lower emissions than agricultural emissions alone.
N2O emissions related to energy are almost all from the combustion of fossil fuels. For example, the combustion of fossil fuels in power plants, cars, and airplanes not only causes CO2 emissions but also emits nitrous oxide (N2O). Any advances to reducing fossil fuel dependency will thus also reduce nitrous oxide emissions.
Most industry-related emissions are from the chemical industry for producing fertilizer, nylon, and similar products. Technologies are available to reduce emissions in these processes.
Nitrous oxide emissions from waste come from, for example, wastewater treatment and landfills.
Wikipedia: Nitrous oxideIPCC: AR6, 5.16 Anthropogenic nitrous oxide (N2O) emissions
Units and Measures
N2O emissions are expressed in the total weight in megatonnes per year. 1 Megatonne is equal to 1 million tonnes.
Wikipedia: MegatonneWikipedia: Global warming potential
About the Data
The last available year in all the emission datasets is 2023. N2O emissions come from the PRIMAP-Hist dataset. It is a rich dataset that combines several published sources to create a historical emissions time series for various greenhouse gases.
The Key Insights paragraph was generated using a large language model (LLM) using a structured approach to improve the accuracy. This included separating the context generation from the interpretation and narrative.
Data Sources
PRIMAP-hist The PRIMAP-hist national historical emissions time series (1750-2023)
Update cycle: Every few monthsDelay: Less than 1 yearCredits: Gütschow, Johannes; Busch, Daniel; Pflüger, Mika (2024): The PRIMAP-hist national historical emissions time series (1750-2023) v2.6. Zenodo.