Context: The Global Nitrous Oxide Assessment has recently been published by the United Nations Environment Programme & the Food and Agriculture Organization.

• It is the first international report focused solely on N2O in more than a decade.

Key Findings

• Global Warming Impact:

• N2O currently contributes 0.1°C to global warming.

• Its continued increase in emissions makes it impossible to limit warming to 1.5°C.

• Anthropogenic Emissions:

• Increased by 40% since 1980, with 75% originating from agriculture (synthetic fertilizers and manure).

• Ozone Depletion and Health Risks:

• N2O is the leading ozone-depleting substance, increasing harmful UV exposure.

• Raises risks of cataracts (0.2–0.8%) and skin cancer (2–10%).

• Abatement measures: The report highlighted that currently, available abatement measures could reduce N2O emissions by more than 40 per cent below current levels.

• Emissions Sources:

• Agriculture: It is currently the source of 75% of those emissions, of which approximately 90% comes from the use of synthetic fertilisers and manure on agricultural soils and 10% from manure management.

• Industry: Industrial sources account for approximately 5% of emissions, and the remaining 20% come from fossil fuel combustion, wastewater treatment, aquaculture, biomass burning, and other sources.

• Rise in Emissions: Atmospheric abundance of the gas has risen by over 20% since pre-industrial era; its mean annual growth rate over the past five years (2017–2021) was 1.2 parts per billion a year and was nearly twice that of the early 2000s (2000–2004).

Suggested Measures

• Agriculture: Use of enhanced-efficiency fertilisers, nitrification inhibitors, & slow-release formulations can reduce emissions.

• Industry: Industries can eliminate N2O emissions by adopting existing and relatively low-cost abatement measures that could cost $1,600-6,000 per tonne of nitrous oxide. 

• Fossil Fuel Reduction: Transition to renewable resources in transportation & energy production.

• Manure Management: Balance nutrient inputs in animal feed, reduce grazing intensity, & apply anaerobic digestion of manure.

• Multilateral Options:  Adopting targets like the Gothenburg Protocol on ammonia & nitrogen oxides under the Convention on Long Range Transboundary Air Pollution.

• Transformations in food production: Transformations in food production and societal systems could lead to even deeper reductions in  Nitrous Oxide emissions.

About Nitrous Oxide (N2O)

• It is a Greenhouse gas (GHG) 300 times more potent than carbon dioxide (CO2).

• It has the third-highest concentration, after CO2 and methane (CH4), in Earth’s atmosphere among GHGs responsible for global warming.

• It can live in the atmosphere for up to 120-125 years and is approximately 270 times more powerful than carbon dioxide per tonne of emission at warming the Earth.

The Gothenburg Protocol

• The Gothenburg Protocol (was adopted in 1999) was established to address pollutants that cause acidification and ground-level ozone. 

• It sets limits on air pollutants including sulfur dioxide, nitrogen oxide, ammonia and volatile organic compounds that are hazardous to human health and the environment.

About Nitrous Oxide (N2O)

• It is a Greenhouse gas (GHG) 300 times more potent than carbon dioxide (CO2).

• It has the third-highest concentration, after CO2 and methane (CH4), in Earth’s atmosphere among GHGs responsible for global warming.

• It can live in the atmosphere for up to 120-125 years and is approximately 270 times more powerful than carbon dioxide per tonne of emission at warming the Earth.

Absorbent “Sinks” of Nitrous Oxide

• Soils: Microbial processes in soils can consume and reduce N2O emissions. 

• Denitrifying bacteria convert N2O to nitrogen gas (N2) under anaerobic conditions.

• Oceans:  Deeper and subsurface oceans absorb N2O from the atmosphere through dissolution at the air-sea interface.

• Marine phytoplankton play a role in consuming dissolved N2O

• Stratosphere: N2O reacts with ozone (O3) which leads to the formation of nitrogen oxides (NOx) and ultimately nitrogen gas (N2).