What is the Breakdown of Human-Induced Yearly N₂O Emissions?

This is a 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: 72% of total N₂O in 2021
• Energy: 11%
• Industry: 6%
• Waste: 5%
• Other: 6%

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.

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 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.

Units and measures

The unit megatonne (Mt) describes the weight of emitted nitrous oxide per year.

Insights from this chart

N₂O emissions from agricultural sources, mostly due to synthetic fertilizer and manure, have by far the largest emissions. These emissions have increased rapidly since the 1940s and are continuing to grow. Emissions in the energy sector from fossil fuel combustion have steadily grown and are now the second-largest contributor to human-induced nitrous oxide emissions, at roughly 10% of total emissions. Historically, there was a period between 1960 and 1990 when emissions from the chemical industry had significant growth, but they have also declined since then.

About the data

The PRIMAP-hist dataset is a rich dataset that combines several published sources to create a historical emissions time series for nitrous oxide and many other greenhouse gasses.

Data sources

PRIMAP-hist The PRIMAP-hist national historical emissions time series (1750-2021)
Credits: Gütschow, J. and Pflüger, M.: The PRIMAP-hist national historical emissions time series (1750-2021) v2.4.2 (2.4.2), https://doi.org/10.5281/zenodo.7727475, 2023.Update cycle: yearlyDelay: 1-2 years