|CWR Presents: : The contribution of soil N2O emissions to the carbon footprint of wheat and biodiesel production in Western Australia
Correctly accounting for soil nitrous oxide (N2O) emissions is necessary when assessing the carbon footprint of agricultural and bioenergy cropping systems. Although soil N2O emissions appear low in relation to N fertiliser inputs [e.g., 1.0% if Intergovernmental Panel on Climate Change (IPCC) default factor employed], the high global warming potential of N2O (298 times greater than CO2), and the increasing amount and area to which N fertiliser is applied, means accurate estimates are required when calculating net greenhouse gas (GHG) emissions from grain and biodiesel production. We measured soil N2O emissions from a rain-fed, cropped soil in a semi-arid region of the Western Australian grainbelt for three years on a sub-daily basis.
The site included N fertiliser (75–100 kg N ha-1 yr-1) and no N fertiliser plots (‘control’). Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (-1.8–7.3 g N2O-N ha-1 day-1) and culminated in 0.09–0.13 kg N2O-N ha-1 yr-1 from the N fertiliser soil and 0.07–0.09 kg N2O-N ha-1 yr-1 from the control. The proportion of N fertiliser emitted as N2O each year, after correction for the control emission (‘background’), was 0.02–0.07%. The emission factor was up to 50 times lower than the IPCC default value for the application of synthetic fertilisers to land (1.0%).
Incorporating locally measured N2O values greatly decreased the carbon footprint of wheat and biodiesel produced from the Western Australian grainbelt. Greenhouse gas emissions decreased from 487 to 304 kg CO2-equivalents per tonne of wheat using local N2O emissions rather than the international default value. Furthermore, utilising locally measured soil N2O fluxes decreased GHG emissions from the production and combustion of one GJ canola based biodiesel from 63 CO2 to 37 CO2 equivalents; with GHG emissions up to 2.1-times lower than that from the production and combustion of one GJ mineral diesel.
We recommend utilising regionally specific estimates of direct soil N2O emissions, and include estimates of indirect N2O emissions, when assessing GHG emissions from grain and biodiesel production from agricultural soils.
LOUISE BARTON1, WAHIDUL BISWAS2, KLAUS BUTTERBACH-BAHL3, RALF KIESE3, DANIEL CARTER4, DANIEL MURPHY1
1School of Earth & Environment, The University of Western Australia, Crawley 6009, Australia
2Centre of Excellence in Cleaner Production, Curtin University, Bentley 6845, Australia
3Karlsruhe Institute of Technology, Institute for Meteorology & Climate Research, Garmisch-Partenkirchen, Germany
4 Department of Agriculture and Food WA, 3 Baron-Hay Court, South Perth 6151, Australia.
Louise Barton,Earth and Environment, Plant Biology, UWA
Blakers Lecture Room, Ground Floor, Mathematics Building, UWA
: 6488 7565
Wed, 16 Nov 2011 16:00
Wed, 16 Nov 2011 17:00
Askale Abebe <[email protected]>
Tue, 22 Nov 2011 17:08
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