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Causes: Nitrous oxide N20


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Nitrous oxide (N2O)

Summary

“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

  • Most N2O emissions in Aotearoa are from agriculture, from manure, dung and urine (cover image & Fig. 2) and adding too much fertiliser to soils. 
  • Once in the ground, 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 poor management of manure (Fig. 3). 
  • 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 have to account for these emissions.
Nitrogen pollution one of the most pressing pollution problems facing humanity

  Causes

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Home > Climate wiki > What causes climate change? > Greenhouse gases > Nitrous Oxide

Summary

“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

  • Most N2O emissions in Aotearoa 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). 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.
Nitrogen pollution one of the most pressing pollution problems facing humanity

Fig. 1: Instructions for this interactive graph (Credit: The 2° 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. 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. 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.
Fig. 4: How combustible fuels are calculated for N2O emissions in New Zealand.

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