Greenhouse gas emissions from food and biofuel production: Contribution of soil N2O emissions - Louise Barton
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Greenhouse gas emissions from food and biofuel production: Contribution of soil N2O emissions - Louise Barton
- 1. Greenhouse gas emissions from food and biofuel production: Contribution of soil N 2 O emissions Louise Barton 1 , Wahidul Biswas 2 , Klaus Butterbach-Bahl 3 , Ralf Kiese 3 , Daniel Carter 4 and Daniel Murphy 1 1 University of Western Australia 2 Curtin University of Technology 3 Department of Agriculture & Food Western Australia 4 Institute for Meteorology & Climate Research, Germany.
- 2. CARBON FOOTPRINTING: Gaining the “Competitive Advantage” “ Climate change affects your company’s competitive landscape in ways you might not realize . Here’s how to map your risks ‒ and opportunities.” Harvard Business Review, 2007 “ As a global business we have an important role in helping to minimise climate change” http://cr2010.tescoplc.com/environment.aspx “ Plan A: We have now set ourselves the ambitious target of becoming the world’s most sustainable retailer by 2051, so that we can lead the way in making a positive contribution to environment and society” http://plana.marksandspencer.com/about
- 3. GREENHOUSE GASES & AGRICULTURAL PRODUCTION Source: Forster et al. 2007. Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , Cambridge University Press. CO 2 -EQU (100 years) SOURCES CO 2 X 1 Transportation, manufacturing inputs, electricity CH 4 X 25 Transportation, manufacturing inputs N 2 O X 298 N fertiliser production, land emissions
- 4. N 2 O FROM SOILS NO 2 - NO N 2 O N 2 N 2 O NO 3 - NH 3 NH 2 OH NO 2 - NO N 2 O N 2 Nitrification Nitrifier Denitrification Denitrification
- 8. REFINING N 2 O EMISSIONS
- 10. 50 cm x 50 cm x variable height (15–95cm)
- 11. DAILY N 2 O EMISSIONS: 3 Years Source: Barton et al. 2010. GCBB 2: 1 ‒ 15 ; Barton et. al. 2008 . GCB 14: 177-192. Wheat Wheat Canola
- 12. ANNUAL N 2 O EMISSIONS In Australia’s <550 mm rainfall regions: N 2 O EF Fert will change from to 0.3% to 0.08% N applied Total loss Emission factor (kg N ha -1 yr -1 ) (%) Canola 2007/08 75 0.13 0.06 Wheat 2006/07 75 0.13 0.02 Wheat 2005/06 100 0.11 0.02 AUST Rainfed crops 0.11–1.2 0.3 GLOBALLY Crops 0.11–17 1.00
- 13. LIFE CYCLE ASSESSMENT: Wheat Production
- 15. WHEAT PRODUCTION GHG EMISSIONS: International N 2 O default value (1.0%) 487 kg of CO 2 equ- per tonne Source: Biswas et. al. 2008. Water and Environment Journal 22: 206-216 Production of urea and superphosphate 24% Production of herbicide 6% N 2 O emissions from paddock 36% Farm machinery production 6% CO 2 emission from urea hydrolysis (from paddock) 19% Transportation of inputs and wheat 9%
- 16. WHEAT PRODUCTION GHG EMISSIONS: ‘ Local’ N 2 O value 304 kg of CO 2 equ- per tonne 35% Source: Biswas et. al. 2008. Water and Environment Journal 22: 206-216 12% operation 27% Prduction of Production of urea and superphosphate 35% Production of herbicide 9% N 2 O emissions from paddock 9% Farm machinery production 8% CO 2 emission from urea hydrolysis (from paddock) 27% Transportation of inputs and wheat 12% 9% 8% paddock 2
- 17. LIFE CYCLE ASSESSMENT: Biodiesel Production & Combustion
- 19. GHG EMISSIONS FROM BIODIESEL PRODUCTION & COMBUSTION : International N 2 O default value (1.0%) 63 kg CO2 equ-/GJ Source: Biswas et. al. 2011. Environmental Science & Technology (accepted). Paddock N 2 O emissions 49% Urea hydrolysis 15% Farm machinery operation 3% Canola seed to oil 2% Fertiliser production 17% 10% Transportation 3% Herbicide & Pesticide production Canola oil to biodiesel 1%
- 20. GHG EMISSIONS FROM BIODIESEL PRODUCTION & COMBUSTION : ‘Local’ N 2 O value 37 kg CO2 equ-/GJ 35% Source: Biswas et. al. 2011. Environmental Science & Technology (accepted). Paddock N 2 O emissions 13 % Urea hydrolysis 25% Farm machinery operation 6% Canola seed to oil 4% Canola oil to biodiesel 2% Fertiliser production 29 % Pesticide production 1 % Herbicide production 16 % Transportation 4 %
- 23. GHG Emissions: Biodiesel vs. Diesel Mineral Diesel Sources: Beer et al. 2007. Report Number KS54C/1/F2.29, CSIRO ; Grant et al . 2008. Report KN29A/WA/F2.5, DAFWA.
Notes de l'éditeur
- Thanks Annette There are two key messages I hope you take away from my presentation this morning: firstly, when calculating the carbon-footprint of agricultural production systems, it is very important that we correctly account for soil N2O emissions; and secondly, obtaining good estimates of these emissions is hard work, but is made easier when we work in national, multidisciplinary teams. Hence the number of authors, which I would like to acknowledge.
- Carbon foot-printing of agricultural products is only likely to increase, especially if it provides a competitive or marketing advantage to business. For example in the UK, both TESCO and Marks & Spencer have commenced a carbon-footprinting program; with TESCO’s stating that they wish to decrease the emissions from the products they sell by 30% by 2020. But unless met targets are underpinned by reliable carbon-foot print calculations, the desired decrease in human-induced GHG may not be achieved.
- There are three main GHG that are considered when calculating the carbon foot print of agricultural products: CO2, CH4 and N2O. And as we all know, these gases vary in their capacity to as GHG . Nitrous oxide is particularly nasty. Its estimated radiative forcing is 298 times that of CO2, which often results in this gas having quite an impact of food and fuel LCAs.
- The single greatest source of nitrous oxide is soil, and in particular soil microbes going about their day-to-day business. A ‘business’ that is highly stimulated by the addition of N fertiliser to the soil.
- Indeed, it is estimated that 1% of N applied to soil will be emitted as N2O. And in the absence of country specific data, this is the value used for calculating their national GHG inventories.
- This default value has been calculated utilising over 200 published data sets. However, data is mainly derived from climates and agricultural management systems very different to ours here in Australia.
- Consequently, we were set the task of measuring soil N2O emissions continuously for three years from a grain production system in south western Australia, and then incorporating these local values into various LCAs to assess their impact. (4.0 min)
- So our first step was to better understand soil N2O emissions from an Australian rain-fed system.
- A site was established at the Cunderdin Agricultural College, in the central wheatbelt of Western Australia, and in a region considered to have a semi-arid environment.
- N2O emissions was measured continuously, every day, seven days a week using an automated chamber system connected to a gas chromatograph designed by our German collaborators.
- Measuring losses every day is time consuming, but important if you take a look at this graph. Here I have plotted daily losses, with time. You can see that these losses vary from 0 to 8 g N/ha. Importantly the greatest losses are not necessaryily in response to N fertiliser, but instead occurred in summer following rainfall events. Without the automatic equipment we would not have captured these fluxes are short-lived.
- The annual losses from the site were consistent, and at the lower end of what has been reported for other Australia soils, and much lower than what is reported internationally. Currently, Australia used an EF of 0.3% for rainfed crops, however this is soon to be further lowered for <550 mm rainfall regions. Fluxes as this site are at the lower end of the range measured for the other N fertilised cereal crops.
- So what is the impact of soil N2O emissions on wheat production in the central wheatbelt of southwestern Australia?
- To answer this question, we conducted a LCA …
- When we utilised the international default factor for calculating soil N2O emissions, we found that soil N2O emissions contributed 36% to the total carbon footprint of the producing and delivering one tonne of wheat to port. CO2 from feriliser production and from the urea fertiliser as it dissolved after it’s application, were also major contributors. Overall, 487 kg CO2 equ- was estimated to be emitted per tonne of wheat.
- Utilising our local N2O values, rather than the default values, lowered the carbon foot print by almost 40%. Soil N2O emissions were now longer single largest source of emissions, but instead CO2 emissions from the production and application of urea to land now account for 62% of the emissions.
- A similar analysis was conducted for biodiesel produced from canola oil.
- Here the goal ….
- When we utilised the international default factor for calculating soil N2O emissions, we found that soil N2O emissions contributed 49% to the total carbon footprint producing and combusting a GJ of energy.
- Utilising our local N2O values, rather than the default values, lowered the carbon foot print by 40%. Soil N2O emissions were now longer single largest source of emissions, but instead CO2 emissions from the production and application of urea to land now account for just over half of the emissions.
- So conclusion …
- Finally, … (11.5 min)
- Out of interest, we compared these GHG emissions with the those produced the production and combustion of 1 GJ of mineral diesel. If we used 100% BD, we found total losses were more than half that of mineral diesel. However, as the biodiesel was blended with mineral diesel, as is generally the case, this advantage was lost. (10.5 min)