US Agricultural GHG Emissions: challenges and opportunities formitigating plot scale vs. whole farm       (and larger) emi...
OUTLINE• US Agricultural GHG Sources and Sinks• GHG intensity and Nitrogen Use Efficiency• Scaling paradox• Farm system em...
US Agricultural GHG Emissions             300             200Tg CO2 eq.             100               0             -100  ...
x                                                                                     F   lu                              ...
IPCC METHODOLOGY FOR N2O                            Direct Emissions   Indirect EmissionsSynthetic N Organic N Residue N  ...
Uncertainty Framework  InputUncertainty      PDF  Input       PDF                       Simulation           Scaling      ...
CO                             N2O gN ha-1 d-1            dr   CO           yla                     nd                    ...
As scale increases, simple models become more reliable                                     US major Crops N2O             ...
as scale decreases, CIs get wider                       1200%                       1000%                       800%      ...
US Corn, Wheat, Cotton, Sorghum Yields                         and N Fertlizer Applied                                    ...
GHG Intensity for N2O from US Corn and Soy                               0.22 g CO2 eq./                                  ...
0.12           Theoretical GHG IntensityN2O CO2-C eq./grain-C                         0.1                        0.08     ...
0.12              DayCent GHG Intensity                   N2O CO2-C eq./grain-C                                           ...
Global Warming Potential                              CO2 eqvt                           (kg CO2eqvt ha-1 y-1)System      ...
Greenhouse Gas Intensity                GHGnet                Crop Yield             GHGISystem        (kg CO2eqvt ha-1 y-...
California Annual Grassland                      Compost Addition Study                   Change in System Carbon due to E...
California Annual Grassland  Compost Addition Study
Current US Farming Practices and Mitigation Outlook50% employ conservation tillage or no tillSmall minority use improved...
Jevon’s Paradox• Many assume that increases in efficiency will solve our problems• Is increasing yield but keeping emissio...
Summary and Issues• Currently available technologies can reduce emissions (in at least some  regions) but incentives are n...
US agricultural GHG emissions: challenges and opportunities for mitigating plot scale vs. whole farm (and larger) emission...
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US agricultural GHG emissions: challenges and opportunities for mitigating plot scale vs. whole farm (and larger) emissions. Delgrosso

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Presentation from the WCCA 2011 conference in Brisbane, Australia.

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US agricultural GHG emissions: challenges and opportunities for mitigating plot scale vs. whole farm (and larger) emissions. Delgrosso

  1. 1. US Agricultural GHG Emissions: challenges and opportunities formitigating plot scale vs. whole farm (and larger) emissions Steve Del Grosso, et al.
  2. 2. OUTLINE• US Agricultural GHG Sources and Sinks• GHG intensity and Nitrogen Use Efficiency• Scaling paradox• Farm system emissions: conventional vs. organic• To what extent does Jevon’s paradox apply?
  3. 3. US Agricultural GHG Emissions 300 200Tg CO2 eq. 100 0 -100 Soil CO2 energy use Soil N2O enteric CH4 manure CO2 CH4+N2O
  4. 4. x F lu etUS Cropped Land Δ Soil C N ils So ic an rg O d te ga ri RP Ir C & o ps Cr er th O s1 in ra ay lG H al Sm p s& ro n C tio ow ta R Ro i n re stu / Pa ay H 40 30 20 10 0 -10 -20 -30 -40 Tg CO2 eq. yr-1
  5. 5. IPCC METHODOLOGY FOR N2O Direct Emissions Indirect EmissionsSynthetic N Organic N Residue N NH3 & NOx Volatilization (10% Synthetic N, 20% Manure N) NO3- Leaching/Runoff (30%) Mineral Soils Organic 0.75% Soils 1% Temperate: 8 kg N2O-N/ha1.0% (applied N) Subtopics: 2.0% (PRP N) 12 kg N2O-N/ha Atmospheric N2O
  6. 6. Uncertainty Framework InputUncertainty PDF Input PDF Simulation Scaling ResultsUncertainty Model Uncertainty PDF 95% Confidence Input Interval PDFUncertainty Structural Uncertainty
  7. 7. CO N2O gN ha-1 d-1 dr CO yla nd 0 5 10 15 20 25 30 35 40 dr w yla he nd at NE cr op dr pi yl ng an d wh ea M NE t Ic or gr IPCC n/ as so s y/ measured al DAYCENT fa lfa CO TNCO co irr irr ig rn ig at ed at ed co co rn rn /b ar le CO y gr O as nt ar s io co Site Level Mean N2O Emissions rn PA cr op perform better than simple models PA gr as s At plot level, process based models usually av er ag e
  8. 8. As scale increases, simple models become more reliable US major Crops N2O 0.6 0.4 Tg N 0.2 0.0 DAYCENT Lower bound DAYCENT Upper bound IPCC Global Anthropogenic N2O 8 6 Tg N 4 2 0 Top Down lower bound Top down upper bound IPCC Del Grosso et al. 2008
  9. 9. as scale decreases, CIs get wider 1200% 1000% 800% CI Width 600% 400% 200% 0%20 25 0 5 10 15 20ion Regional N2O Emisisons (gG N) Most of this uncertainty is due to model structure Del Grosso et al. 2010
  10. 10. US Corn, Wheat, Cotton, Sorghum Yields and N Fertlizer Applied N fert Tg45 grain yield Tg * 1040353025201510 5 0 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 0919 19 19 19 19 19 19 19 19 19 20 20 20 20 20 20 20 20 20 20 NUE is increasing
  11. 11. GHG Intensity for N2O from US Corn and Soy 0.22 g CO2 eq./ g grain 0.29 gCO2/ g grain GHG intensity is decreasing
  12. 12. 0.12 Theoretical GHG IntensityN2O CO2-C eq./grain-C 0.1 0.08 0.06 0.04 0.02 0 0 5 10 15 20 25 30 35 N inputs g N m-2
  13. 13. 0.12 DayCent GHG Intensity N2O CO2-C eq./grain-C 0.1 0.08 0.06 0.04 0.02 0 0 5 10 15 20 25 30 35 N inputs g N m-2 Irrigated Corn CO - N2O GHG Intensity 0.06 0.05CO2-C eq/grain-C 0.04 0.03 0.02 0.01 0 0 N NT no- corn 0-N, corn NT 0 N 0-N, corn Hi-N, no- High Hi-N, High N NT corn N CT till conventional- till conventional- till till
  14. 14. Global Warming Potential CO2 eqvt (kg CO2eqvt ha-1 y-1)System Soil C N2O Energy GHGnetNo-Till 0b 303 b 807 1110 bChisel Till 1080 a 406 ab 862 2348 aOrganic -1953 c 737 a 344 -872 c Cavigelli et al. 2009
  15. 15. Greenhouse Gas Intensity GHGnet Crop Yield GHGISystem (kg CO2eqvt ha-1 y-1) (Mg ha-1 y-1) (kg CO2eqvt Mg grain-1)No-Till 1110 b 7.25 a 153 aChisel Till 2348 a 7.14 a 330 aOrganic -872 c 5.12 b -169 b Cavigelli et al. 2009
  16. 16. California Annual Grassland Compost Addition Study Change in System Carbon due to Enhanced Production 1800 1600 Compost carbon 1400 Change in system carbon 1200g C m-2 1000 800 600 400 200 0 2008 2012 2016 2020 2024 2028 The change in system carbon is the total system carbon from the compost simulation minus the compost carbon. This represents the carbon sequestration due to enhanced plant production. Updated 13 July 2011
  17. 17. California Annual Grassland Compost Addition Study
  18. 18. Current US Farming Practices and Mitigation Outlook50% employ conservation tillage or no tillSmall minority use improved fertilizersMost farmers do not greatly exceed recommended ratesSlow release fertilizers and nitrification inhibitors aremore effective in the drier western USPractices that reduce direct N2O are also likely to reduceindirect N2OUrease inhibitors may increase direct N2OModel results suggest that rates could be reduced withstabilized N sources, but need observations to verify
  19. 19. Jevon’s Paradox• Many assume that increases in efficiency will solve our problems• Is increasing yield but keeping emissions constant (or decreasing) the same as deceasing emissions but keeping yield constant (or increasing)?• Probably not – as efficiency increases people tend to consume more• So absolute emissions will continue to increase
  20. 20. Summary and Issues• Currently available technologies can reduce emissions (in at least some regions) but incentives are needed• at small scales, fluxes can be measured precisely and accurately, but models usually do better at large scales.• Benefits of stabilized N likely scale up to the farm system level and include improved water and air quality• However, entity level observations are not feasible and model uncertainty at the farm scale is huge• If GHG intensity is minimized then yields would plummet• If increasing NUE is the goal then BAU is sufficient• If the goal is to increase yields and decrease absolute emissions then things get challenging• Need to define life cycle analysis boundaries carefully

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