Improved estimates of nitrous oxide emissions and emission factors for New Zealand
What is the problem?
New Zealand is required to produce an annual inventory of greenhouse gas (GHG) emissions under the UNFCCC (United Nations Framework Convention on Climate Change). Nitrous oxide emissions make up about 14% of our anthropogenic GHG emissions and are of growing importance because of agricultural intensification. But nitrous oxide emissions have proven very difficult to estimate because they are highly variable over space and time. When agriculture enters the Emissions Trading Scheme, estimates of nitrous oxide emissions produced by each participant will be needed. New Zealand therefore needs its own specific capacity to estimate nitrous oxide emissions so it can report accurately and develop technologies to reduce them.
How did we approach resolving the problem?
In association with the Ministry for Primary Industries (MPI) Policy and other national and international researchers, NzONet (New Zealand Nitrous Oxide Network), New Zealand Agricultural Greenhouse Gas Research Centre and Pastoral Greenhouse Gas Research Consortium, and Global DNDC (denitrification /decomposition) Network we identified the research priorities. We used especially designed chambers to collect nitrous oxide samples from dairy and sheep pastures, and successfully took measurements to paddock scale. We adapted the DNDC model to grazed pasture systems and tuned it to New Zealand’s climate conditions, soils, and pasture management.1 The adapted model was extended to assess the changes in farm-, regional- and national-scale GHG emissions resulting from expected changes in management and climate,2 and improved to capture the effect of uneven spatial distribution of urine deposits.3 We can now show where, and to what degree, emissions are a problem.4
Who has adopted our innovation?
MPI, the poultry industry, DairyNZ, New Zealand Beef & Lamb, the fertiliser industry; and national and international researchers and modellers.
What impact has this innovation had on adopters?
- Reduced the poultry industry emissions liability by 50% by improving estimates and replacing default values by New Zealand-specific information5
- Reduced annual indirect emissions from urease inhibitor treated total fertiliser N by 4.8 Gg CO2-equiv. with an overall annual reductions potential of 47.7 Gg CO2-equiv by using a NZ specific value of 0.055 for fraction of emitted as NH3 reduces6
- Confirmed 50% on average reduction in nitrous oxide emissions from urine patches by DCD application from 3-year nitrous oxide mitigation research (NOMR) in Manawatu (Landcare Research), Waikato and South Otago (AgResearch), and Canterbury (Lincoln University)7
- Potential to significantly reduce emissions liability of sheep and beef sector from improved nitrous oxide emission estimates from hill country pastures (With AgResearch, MPI, New Zealand Beef & Lamb)
1Saggar S, Giltrap DL, Li C, Tate KR 2007. Modelling nitrous oxide emissions from grazed grasslands in New Zealand. Agriculture, Ecosystems & Environment 119: 205–216.
2Saggar S 2009. Managing Climate Change (MC2): Whakamarama 58. (17 Dec 09).
3Giltrap DL, Saggar S 2010. Modelling the effects of spatial distribution of urine patches on N2O emissions using NZ-DNDC. In: Farming’s future: Minimising footprints and maximising margins. Occasional Report No. 23. Fertiliser & Lime Research Centre, Massey University, Palmerston North. Pp. 262–267.
4Giltrap D, Saggar S, Li C, Wilde H 2008. Using the NZ–DNDC model to estimate agricultural N2O emissions in the Manawatu–Wanganui region. Plant and Soil 309: 191–209.
5Saggar S, Giltrap D, Hill J 2011. Methane, nitrous oxide and ammonia emissions from poultry: emission factors and uncertainty analysis.Landcare Research Report LC265, prepared for PIANZ, Auckland. 58 p.
6Saggar et al. 2012. Science of the Total Environment (STOTEN): in press.
7Gillingham AG, Ledgard SF, Saggar S, Cameron KC, Di HJ, de Klein CAM, Aspin MD 2012. Initial evaluation of the effects of dicyandiamide (DCD) on nitrous oxide emissions, nitrate leaching and dry matter production from dairy pastures in a range of locations within New Zealand. Occasional Report No. 25. Fertiliser & Lime Research Centre, Massey University, Palmerston North. http://flrc.massey.ac.nz/publications.html. 16 p.