Global nitrous oxide emissions from human activities have increased by 40% between 1980 and 2020, primarily due to farming practices, according to a new study by international research project, the Global Carbon Project.
In 2020, more than 10 million metric tonnes of nitrous oxide – a greenhouse gas (GHG) “more potent” than carbon dioxide (CO2) or methane – were released into the atmosphere, mainly through farming, the study shows.
Agricultural production accounted for 74% of human-driven nitrous oxide emissions in the 2010s, which can be attributed primarily to the use of commercial fertilisers and animal waste on croplands, researchers said.
The report Global Nitrous Oxide Budget 2024 published in the journal Earth System Science Data today (Wednesday, June 12), was led by researchers from Boston College in Massachusetts, US.
Nitrous oxide
The rate at which nitrous oxide was released into the atmosphere in 2020 and 2021 was faster than in any previous year since measurements began in 1980, the study produced by 58 researchers from 55 organisations in 15 countries shows.
Nitrous oxide has a global warming potential approximately 300 times larger than CO2. Once emitted, the GHG stays in the atmosphere for 117 years, according to the Global Carbon Project.
While global CO2 emissions from human activities, such as fossil fuels and land use change, have been “rather stable” over the past decade, global nitrous oxide emissions, largely from food production, continue to rise, the study shows.
Agricultural emissions reached eight million metric tonnes in 2020, a 67% increase from the 4.8 million metric tons released in 1980, which the researchers attributed to an increase in the use of commercial nitrogen (N) fertilisers and manure production.
The use of N fertilisers in agriculture, including livestock manure production and use, is the “single largest” human-driven source of nitrous oxide in the atmosphere, according to the international researchers.
Emissions from agriculture continue to grow, while other sectors, such as fossil fuels and the chemical industry, are globally not growing or declining.
Fossil fuel combustion and certain industrial processes contribute 17% to these emissions, the study shows.
Which countries emit the most?
The top five emitting countries of human-driven nitrous oxide emissions in 2020 were China (16.7%); India (10.9%); the US (5.7%); Brazil (5.3%); and Russia (4.6%).
Pakistan, Australia, Indonesia, Turkey, and Canada are in the top 10 emitters.
China, India, the US, Brazil, and Russia also have the highest nitrous oxide emissions per person. These are influenced by both domestic consumption and the trade of food and food products, the researchers said.
The EU, Japan and Korea have reduced their human-driven nitrous oxide emissions over the past decades, while in China emissions have been declining for the past five years due to increased nitrogen use efficiency, the study shows.
The EU reduced its nitrous oxide emissions by 31%, the largest decrease of any region, mostly due to reductions from fossil fuel and industry emissions in the 1990s. However, agricultural emissions have not declined over the past two decades.
Developing countries in Africa and south and southeast Asia show a “significant increase” in N fertiliser use, albeit coming from low values.
Nitrous oxide emissions in Pakistan and Ethiopia grew by over 200%, according to the research.
Brazil’s nitrous oxide emissions grew strongly over the past two decades, with direct emissions from the use of fertilisers and manure more than double, according to latest research by the Global Carbon Project.