Global N2O Budget Synthesis

Most of us know nitrous oxide as “laughing gas,” used for its anesthetic effects. But nitrous oxide (N2O) is the third most important long-lived greenhouse gas, after carbon dioxide (CO2) and methane. Nitrous oxide is also one of the main stratospheric ozone depleting substances.

The newest update to the global nitrous oxide (N2O) budget by Tian et al. has come out in 2024. About 60-70% and anthropogenic emissions of N2O are shown to come from agriculture. Unfortunately, N2O emissions are increased mostly unabated, and the rate of increase is accelerating.

Below us an updated diagram from the new paper:

Diagram depicting the global nitrogen dioxide budget from the paper by Tian et. al 2024.

Davidson summarized the agricultural sources of N2O and the many challenges to abate them in a 2023 Catalyst podcast interview with Shayle Kann.

The global N2O budget is also featured in a seminar presented by Dr. Davidson at the Appalachian Laboratory’s Fall 2020 Seminar Series.

Global emissions of N2O specifically from livestock manure are inventoried in a recent paper by Zhang et al in Global Change Biology.

Fortunately, we have the knowledge base and tools to mitigate N2O emissions from agriculture. An analysis of the global potential for mitigation of emissions from agriculture is provided by Cui et al. in One Earth.

In contrast to agricultural emissions, industrial emissions of N2O are smaller, However, Davidson and Winiwarter (2023) show that industrial N2O emissions produced as a side effect of synthesizing adipic acid (used for nylon) and nitric acid (used for fertilizers, explosives, and adipic acid) could be brought to nearly zero quickly with affordable technologies that already exist. This is a low-hanging fruit for near-term climate mitigation, but many governments, industries, and consumers don’t seem to be aware of it. For example, 65% of the N2O emissions embodied in nylon products globally are used in passenger cars and light vehicles; automobile manufacturers could require supply chains to source nylon exclusively from plants that deploy efficient N2O abatement technology, with only a trivial increase in cost for vehicle manufacturing.

A paper in Nature Climate Change (https://doi.org/10.1038/s41558-019-0613-7) by Thompson et al, (2019) uses inversions of observations of atmospheric concentrations of N2O to deduce spatial and temporal variation of sources from oceans and the continents.
“We see that the N2O emissions have increased considerably during the past two decades, but especially from 2009 onwards,” said lead scientist Rona L. Thompson from NILU–Norwegian Institute for Air Research. “Our estimates show that the emission of N2O has increased faster over the last decade than estimated by the Intergovernmental Panel on Climate Change (IPCC) emission factor approach.”

This publication and the recent global budget by Tian et al. demonstrate how current efforts are falling short in most regions of the world. In Europe and North America, we have succeeded in decreasing growth in nitrous oxide emissions, but unfortunately, the same can’t be said for Asia and South America, where fertilizer use, intensification of livestock production, and the resulting nitrous oxide emissions are growing rapidly.
Because N2O affects both climate change and stratospheric ozone depletion, calculation of the “social cost of N2O” must include both, which, as shown in the publication by Kanter et al. (2021. Improving the social cost of nitrous oxide. Nature Climate Change, https://doi.org/10.1038/s41558-021-01226-z), elevates its calculated cost to society.

The Climate and Clean Air Coalition (CCAC) of the United Nations Environment Program is launching a global assessment of N2O to highlight the urgent need for abatement actions. Davidson is a coordination lead author of the chapter on “Implementing Priority N2O Mitigation Measures.” The assessment will be presented to the UNFCCC Conference of the Parties ad to the Montreal Protocol Meeting of the Parties in November 2024.