(Image: Etienne Giradet)
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
- 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, it contributes 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.
Fig. 1: Instructions for this interactive graph (Credit: The 2°
- 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
- Ministry for the Environment: New Zealand Emissions Trading Scheme
- Ministry for the Environment: Climate Change Response (Zero Carbon) Amendment Act
- Ministry for the Environment: 2019 Measuring Emissions: A Guide for Organisations
- Ministry for the Environment: 2019 Measuring Emissions: A Guide for Organisations. 2019 Summary of Emission Factors
- Ministry for Primary Industries: Agricultural Inventory Advisory Panel
- Maanaki Whenua Landcare Research: Agricultural greenhouse gasses
- Maanaki Whenua Landcare Research: Modelling Nitrous Oxide Emissions
- 2020: Tian et al; A comprehensive quantification of global nitrous oxide sources and sinks, Nature 586, pp248–256
- 2019: IPCC: Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
- 2016: van d r Weerden et al; Nitrous oxide emissions from urea fertiliser and effluent with and without inhibitors applied to pasture, Agriculture, Ecosystems and Environment 219, 58-70
- 2013: IPPC; Chapter 8: Anthropogenic and Natural Radiative Forcing in: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change