Nitrous oxide (N₂O) is a greenhouse gas 270 times more potent than carbon dioxide, and levels are rising faster than expected, according to the United Nations Global Nitrous Oxide Assessment. The gas is at the top of the list of ozone-layer destroying substances, and it’s responsible for 10 percent of net global warming since the Industrial Revolution. Without urgent action, there will be no way to meet the goal of capping global warming at 1.5° Celsius, the assessment warns, as it was announced at the 2024 United Nations Climate Change Conference (COP29) in Baku, Azerbaijan.
There are measures using technology available today that can reduce anthropogenic N₂O emissions (emissions caused by people, as opposed to natural sources) by more than 40 percent. Further reductions are possible through deeper transformations in food production, chemical industries and the burning of fossil fuels and biomass.
“This Assessment sounds the alarm on a relatively forgotten super pollutant that contributes greatly to climate change and air pollution,” Martina Otto, at the Climate and Clean Air Coalition, said in a statement. “By using the abatement tools highlighted in the Assessment that are already available to us, we can yield multiple benefits across climate, clean air, and health,” she added.
These are the N₂O challenges and some of their solutions.
Where does N₂O come from?
Atmospheric nitrous oxide concentrations rose from 301 to 336 parts per billion between 1980 and 2022, an increase driven mostly by the world’s farms. Agriculture is responsible for 75 percent of anthropogenic N₂O emissions. Ninety percent of that stems from fertilizer, both synthetic and organic. Ten percent is linked to manure management. Chemical industries account for 5 percent of the N₂O people are dumping into the atmosphere. That includes nitric acid, which is key in the manufacture of fertilizers. The remaining 20 percent comes from burning fossil fuels and biomass, wastewater treatment and other activities.
A rising global temperature is catastrophic, but not the only consequence of N₂O emissions. The gas is at the head of the pack of ozone-depleting chemicals, posing a global threat of increased exposure to the sun’s ultraviolet light. The result may be higher risks of skin cancer and cataracts. It is also implicated in air pollution and linked to premature deaths. Curbing emissions could prevent up to 20 million premature deaths worldwide by 2050, according to the assessment.
“A sustainable nitrogen management approach not only reduces nitrous oxide emissions but also prevents the release of other harmful nitrogen compounds,” A.R. Ravishankara, Co-Chair of the Assessment at Colorado State University, said in a statement. “This could improve air and water quality, protect ecosystems, and safeguard human health, all while maintaining food security.”
How farms can halt the rise of N₂O
The UN’s assessment outlines measures that farms and industries can take today to stop the rise of N₂O and reduce the emissions by more than 40 percent of current levels by 2050. Most of the anthropogenic N₂O comes from farms, and most of the actions to reduce emissions are available to farms as well. This is a quick list of abatement measures, according to the assessment.
- Soil and plant nitrogen testing
- Controlled-release fertilizers, reduced rates of application; and increased manure recycling
- Crop management through integrating nitrogen-fixing crops in rotations; reduced tillage; and the use of cover crops
- Optimize the diets of livestock and reduce protein consumption in certain regions that consume high volumes of animal products
- Rotational grazing
- Store solid manure and slurry separately in dry containers, dry manure rapidly and employ anaerobic digestion
- Build buffer strips for drainage control
- Integrate crop and livestock production
One measure that’s missing from the list above is to increase the use of organic fertilizer. While it may seem a likely solution, organic fertilizer also emits N₂O. In fact, research suggests synthetic fertilizer might contribute less N₂O than organic manures and slurries under some conditions. Soil composition and climate could dictate which kinds of fertilizer are best for managing N₂O, according to a study published in the journal Agriculture, Ecosystems & Environment by Søren Petersen at Aarhus University in Denmark and colleagues.
Innovative designs that can have an impact
Startups have developed technological solutions that can reduce N₂O emissions by optimizing the usage of fertilizers and irrigation and testing for nitrogen. The list also includes biochar, which is included in the UN assessment and can change soil ammonium and nitrate concentrations in soil, research suggests. The following products and services are featured in the Engineering for Change Solutions Library, developed to serve low-income communities worldwide.
