Nitrous oxide (N2O), after carbon dioxide (CO2) and methane (CH4), is the third most important greenhouse gas for the enhanced greenhouse effect. Nitrous oxide (N2O) is naturally present in the atmosphere as part of the Earth's nitrogen cycle and can come from a variety of sources such as agriculture, fossil fuel combustion, wastewater management, and industrial processes. In this article, we will discuss Nitrous Oxide as a Greenhouse Gas which will be helpful for UPSC exam preparation.

What is Nitrous Oxide?

• Nitrous oxide (N2O) gas is different from nitric oxide (NO) or nitrogen dioxide (NO2). Although nitric oxide and nitrogen dioxide are not greenhouse gases, they do play a role in the formation of tropospheric ozone.
• NO and NO2 emissions cause global cooling by forming (OH) radicals that damage methane molecules, thereby balancing the effect of GHGs.
• N2O is 300 times more potent than carbon dioxide (CO2).
• N2O is also the only remaining threat to the ozone (O3) layer because, like CO2, it accumulates in the atmosphere over time and can survive in the atmosphere for up to 125 years.
• Its global concentration levels grew by 20% from 270 parts per billion (ppb) in 1750 to 331 ppb in 2018.
• Agriculture, fuel combustion, wastewater management, and industrial processes all contribute to an increase in the amount of N2O in the atmosphere.

Nitrous Oxide as a Greenhouse Gas

• Nitrous oxide is naturally present in the atmosphere as part of the Earth's nitrogen cycle, and it comes from a variety of sources.
• Nitrous oxide molecules spend an average of 114 years in the atmosphere before being removed by a sink or destroyed by chemical reactions.
• As a greenhouse gas, nitrous oxide has significant global warming potential.
• Nitrous oxide has 298 times the atmospheric heat-trapping ability of carbon dioxide (CO2) per molecule over 100 years.
  • However, due to its low concentration (less than 1/1,000 of that of CO2), its contribution to the greenhouse effect is less than one-third that of CO2, and also less than water vapor and methane.
• Nitrous oxide is primarily produced by humans through the combustion of fossil fuels, biomass burning, the industrial production of nitric acid, and the application of fertilizers to agricultural crops.
• Nitrous oxide, like carbon dioxide, contributes to the greenhouse effect by absorbing reradiated infrared radiation from the Earth's surface and warming the troposphere (lower atmosphere).
• It is chemically inert in the troposphere and remains there for about 120 years before moving into the stratosphere, where it eventually destroys stratospheric ozone.
• Human activity has increased the concentration of nitrous oxide in the atmosphere.

Sources of Nitrous oxide

Natural Sources

• Nitrous oxide emissions occur naturally from a variety of sources related to the nitrogen cycle, which is the natural circulation of nitrogen among the atmosphere, plants, animals, and soil and water microorganisms.
• Nitrous oxide is naturally produced by microbial activity in soils and the ocean, and the gas produced by the microbes is released into the atmosphere.

Anthropogenic Sources

• Nitrous oxide can be produced by a variety of agricultural soil management activities, including the application of synthetic and organic fertilizers and other cropping methods, manure management, and agricultural residue burning.
• Nitrous oxide is emitted when people add nitrogen to the soil using synthetic fertilizers.
• According to a research paper published in October 2020, agricultural soils is responsible for more than 70% of N2O emissions from India in 2010, followed by wastewater (12%) and residential and commercial activities (6%), and N2O has surpassed methane as the second-largest greenhouse gas from Indian agriculture since 2002.
• Nitrous oxide is also emitted during the breakdown of nitrogen in livestock manure and urine, accounting for 6% of N2O emissions in 2010.
• Nitrous oxide is emitted when transportation fuels are burned.
• Nitrous oxide is produced as a byproduct of the production of nitric acid, which is used to manufacture synthetic commercial fertilizer, and adipic acid, which is used to manufacture fibers such as nylon and other synthetic items.
• Nitrous oxide is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.
• Nitrous oxide is also produced during the nitrification and denitrification of nitrogen present in domestic wastewater, which is typically in the form of urea, ammonia, and proteins.

Measures to Reduce Nitrous Oxide Emission

• Emissions can be reduced by using less nitrogen-based fertilizer and applying it more efficiently, as well as by changing a farm's manure management practices.
• Because nitrous oxide is a byproduct of fuel combustion, reducing fuel consumption in automobiles and secondary sources can help to reduce emissions.
• Implementation of pollution control technologies can reduce N2O emissions.
• Because nitrous oxide is generally emitted from industry through the combustion of fossil fuels, technological advancements and fuel switching are effective methods of reducing N2O emissions from industry.
• There are well-established methods and technology for mitigating N2O emissions, such as crop and manure management and the use of bio-fertilizers, that must be fully utilized.
• Globally revised industrial and agricultural policies will significantly reduce such emissions.
• Reducing GHG emissions will also result in less air and water pollution.
• There is a need to include non-carbon sources in key global climate change negotiations.
• It is possible to reduce N2O emissions if countries execute the United Nations Global Campaign on Sustainable Nitrogen Management.

Conclusion

The agriculture industry contributed significantly to N2O emissions over the last four decades, primarily due to the use of nitrogen-based fertilizers. Since 2015, India has been able to restrict the growth of nitrogen emissions due to a neem-coating of urea policy that has reduced atmospheric loss of the element as well as soil contamination. Dedicated and coordinated efforts by member countries to commit to a goal and develop innovative technologies may help reduce nitrous oxide emissions.

FAQs

Question. What is nitrous oxide (N₂O)?

Question. How does N₂O contribute to climate change?

Question. What are the primary sources of nitrous oxide emissions?

Question. Why is N₂O more potent than CO₂?

Question. What measures can reduce N₂O emissions?

MCQs

1. Which of the following gases is commonly referred to as 'laughing gas'?

A) Carbon dioxide

B) Methane

C) Nitrous oxide

D) Sulfur dioxide

2. Nitrous oxide has a global warming potential (GWP) approximately how many times higher than CO₂?

A) 10 times

B) 100 times

C) 300 times

D) 1,000 times

3. The main anthropogenic source of nitrous oxide is:

A) Automobile emissions

B) Fertilizer usage in agriculture

C) Coal combustion

D) Aerosol sprays

4. In addition to being a greenhouse gas, N₂O also affects:

A) Soil acidity

B) Ozone depletion

C) Ocean currents

D) Solar radiation

5. Which strategy would most effectively reduce N₂O emissions from agriculture?

A) Increasing pesticide use

B) Promoting precision farming and reduced nitrogen fertilizers

C) Utilizing more fossil fuels

D) Introducing more tilling practices

GS Mains Questions and Model Answers

Q1: Discuss the role of nitrous oxide in global warming and the challenges in mitigating its emissions.

Answer: N₂O has high global warming potential and contributes to ozone depletion. Its emissions largely stem from agriculture, waste management, and industry. Challenges in mitigation include overuse of nitrogen-based fertilizers, inadequate waste treatment, and difficulty in managing diffuse sources across sectors.

Q2: Examine the environmental impact of agricultural practices on nitrous oxide emissions and suggest measures to reduce them.

Answer: Agricultural activities, especially through fertilizers and manure management, are primary sources of N₂O. Reduction strategies include optimizing fertilizer application, promoting nitrogen-use efficiency, adopting crop rotation, and precision agriculture techniques.

Q3: Why is controlling nitrous oxide emissions critical in climate change mitigation efforts?

Answer: N₂O's long atmospheric lifespan and high warming potential make it crucial in climate action. Effective control can be achieved through targeted agricultural reforms, emissions monitoring, and international cooperation.

Previous Year Questions on Nitrous Oxide

1. UPSC CSE 2020

Question: "Discuss the impact of greenhouse gases other than carbon dioxide on global warming."

Answer: While CO₂ is widely recognized, gases like N₂O, methane, and CFCs have higher per molecule warming potentials. N₂O persists in the atmosphere for decades and impacts both warming and ozone depletion. Addressing these gases requires targeted emission controls and international treaties like the Kigali Amendment to the Montreal Protocol.

2. UPSC CSE 2018

Question: "What are the major sources and environmental impacts of nitrous oxide emissions in India?"

Answer: Major sources in India include agriculture, especially from nitrogen fertilizers, and waste management. Environmental impacts involve climate warming, stratospheric ozone depletion, and regional air quality issues. Policy interventions like fertilizer management and waste processing reforms are essential for mitigation.