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Causes: nitrous oxide

Causes: nitrous oxide


Nitrous Oxide (N2O)


  • Nitrous oxide (N2O) is 298 times more potent than carbon dioxide (298CO2-e) and is the third-largest contributor to man-made (anthropogenic) greenhouse gasses after carbon dioxide and methane, itcontributes to the destruction of the ozone layer, and the amount in the atmosphere is dramatically increasing (Fig. 1).
  • Most N2O emissions in NZ are from agriculture, mainly manure, dung and urine in soils (cover image & Fig.2) where microorganisms reduce nitrogen oxides to nitrogen gas (denitrifying microbes) or by converting soil ammonium to nitrate (nitrifying microbes). It’s also produced in meat and dairy processing, and through the management of manure (Fig. 3). Plus nitrogen fertilisers break down to N2O and carbon dioxide. (Limestone and dolomite fertilisers break down to produce CO2).
  • Sources from burning fuel depend on how that fuel is burned (combusted) (Fig. 4).
  • Under the current  NZ Emissions Trading Scheme and Climate Change Response (Zero Carbon) Amendment Act, the agricultural sector does not yet have to account for these emissions.

“The recent growth in N2O emissions exceeds some of the highest projected emission scenarios, underscoring the urgency to mitigate N2O emissions.” – Tian et al, 2020

Fig. 1: Instructions for this interactive graph (Credit: The Institute.)

  • Mouse over anywhere on the graph to see the changes in global atmospheric N2O over the last thousand years.
  • To see details for time periods of your choice, hold your mouse button down on one section then drag the mouse across a few years, and release it.
  • To see how this compares to the past 771,000 years, click on the ‘time’ icon on the top left.
  • Compare this to rising global temperatures by clicking the planet/thermometer icon at the top left corner.
  • To return the graph to its original position, double-click the time icon to the left of the thermometer/planet icon
Fig. 2: Emissions from soils used for agriculture in NZ. The yellow highlight show the amount of N2O that comes from soil used per animal. As the total CO2-e (blue highlight) in soils comes exclusively from N2O, the values in both highlighted columns is the same.
Fig. 3: Emissions from agricultural manure (urine and dung) in NZ. The proportion of N20 emitted is much less than that of methane (CH4).
Fig. 4: How combustible fuels are calculated for N2O emissions in New Zealand.

References and further reading