Nitrous oxide (N2O) is the third most prevalent of the anthropogenic greenhouse gases (GHGs) making up 6% of global emissions. [Note that this is NOT nitrogen dioxide (NO2)] Nitrous oxide has ~298 times the heat trapping power of carbon dioxide. In other words, one kilogram of nitrous oxide released into the atmosphere has the warming equivalent of 298 kgs of CO2.

More than three-quarters of N2O emissions in the US come from agriculture practices, specifically the addition of nitrogen-based fertilizers that are essential to industrial agriculture practices. Livestock manure also contributes to N2O emissions. Fossil-fuel combustion, mostly in cars, releases a portion of the N2O emissions. Like other GHGs, nitrous oxide concentrations in the atmosphere have increased exponentially since the 1950s. The figure below shows the rate of nitrogen fertilizers in the US since 1860.

Peiyu Cao, Chaoqun Lu, and Zhen Yu
Department of Ecology, Evolution, and Organismal Biology, Iowa State University
Earth Systems Science Data, 10, 969–984, 2018

The map below shows the varied rate of nitrogen fertilizers used per hectare in nations around the world in 2017. The darker the blue, the higher the rate of fertilizer use per hectare (~2.5 acres).

The figure below shows that increased rate of nitrogen fertilizer consumption over time by region. Remember that geographic regions are one unit of measure and they don’t account for different population sizes, levels of development, or measure equivalent areas of land.

Overall, the rate of nitrous oxide emissions in the US has remained flat or at a similar rate since 1990. Reductions have been achieved through policies that reduced automobile emissions but those reductions have been offset by increases in fertilizer use. Globally (which is an important measure when dealing with a global phenomenon) atmospheric concentrations continue to rise.

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