Inventorying Agricultural Soil Greenhouse Gas Emissions: Methods Used by Annex 1 Countries

1. Inventorying Agricultural Soil Greenhouse Gas Emissions: Methods Used by Annex 1 Countries Erandi Lokupitiya and Keith Paustian Colorado State University

2. Global commitment towards mitigating greenhouse gas emissions • Adoption of the United Nations Framework Convention on Climate Change (UNFCCC) in 1992 • Adoption of the Kyoto) Protocol in 1997 (Ratified and implemented Feb 2005 • Member countries are expected to submit national GHG inventories prepared using comparable methodologies (IPCC revised guidelines and Good Practice Guidance) • Annual submissions are made by Annex 1 (developed) countries

3. Major GHG sectors under the UNFCCC/Kyoto Protocol Energy Industrial processes Solvent and other product use Agriculture Land-Use Change and forestry Waste

4. Source/sink categories under the agricultural sector Manure management Enteric fermentation Rice cultivation Agricultural soils Burning of agricultural residues Prescribed burning of savannas

5. IPCC inventory methodology • Tier 1- simple equations and default emission factors • Tier 2- default equations with country-specific parameters that better account for climate, soil, management and other local conditions • Tier 3- country-specific methods that may include more complex models and inventory systems

6. IPCC inventory methodology contd.. Estimation of N2O emissions from agricultural soils • direct N2O emissions from agricultural soils 2) direct soil emissions of N2O from animal production (livestock grazing) 3) indirect emissions of N2O from N used in agriculture (losses from N volatilization and leaching)

7. IPCC inventory methodology contd.. Estimation of direct N2O emissions: N2O DIRECT (kg N/yr) = [FSN + FAW + FCR + FBN] * EF1 + FOS * EF2 FSN =N input from synthetic fertilizer use; FAW = N from livestock manure applied to soil; FBN = total N input in N-fixing crops; FCR = N input from crop residues; FOS = Area of cultivated Organic Soils; EF1 = Emission factor for emissions from N inputs EF2= Emission factor for emissions from organic soil cultivation

8. Evaluation of IPCC default methodology for N2O estimation • Universal, and allows comparability among the national estimates by different countries • Likely statistical bias in data - for N2O. Most studies have been done in temperate countries • Method does not reflect variation among different crops, soils and climates that can influence N2O production

10. IPCC inventory methodology contd.. Estimation of emissions/ removals of CO2 from agricultural soils: 1) Changes in C stored in mineral soils due to changes in land-use practices 2) Cultivated organic soils 3) Liming of agricultural soils

11. IPCC inventory methodology contd.. Estimation of changes in mineral soil C stocks SC = [(SCt – SC(t-D)* A]/D SCi = SCR* FLU* FMG* FI SC = annual SOC stock change SCt = SOC stock at time t SC(t-D) = SOC stock at time t-20 years SCR = reference carbon stock FLU, FMG, FI = stock change factors for LU and management D= Duration (default is 20 years).

12. Evaluation of IPCC methodology for estimation of CO2 emissions • allows comparability among countries • Takes into account the spatial variability associated with soil type, climate and management regime. • Relatively high uncertainty in global default stock change and emission factors

13. CORINAIR (CORe INventory of AIR emissions in Europe) methodology- European Union • Includes an improved methodology for N2O based on multivariate regression analyses incorporating climate, weather and soil conditions, etc. • No alternative methodology suggested for estimating CO2 emissions. But higher emission factors compared to IPCC has been suggested for CO2 released from cultivated organic soils • can be transformed to IPCC format based on the information in the Annex 2 of the Volume 1 of revised IPCC guidelines

14. Country specific methods developed by certain Annex1 countries

15. Australia National Carbon Accounting System (NCAS) • A model-based accounting system, based on resource inventories, field studies, remote sensingand modeling • Full C Accounting Model (FullCAM) for estimating land use change emissions associated with biomass and soil C pools • Five component models: 3PG (forest growth), CAMFor (forest systems), CAMAg (agricultural systems), GENDEC (microbial decomposition), Roth-C (agricultural soil C) • Requirement of time-series consistency in estimating GHG from land use change is well met by NCAS

16. Results from NCAS Source: Australian Greenhouse Office

17. AustriaAustrian Carbon Balance Model (ACBM) • Model covers five national subsystems including agriculture • Agricultural soil C dynamics are estimated using a three pool model. • Net emissions from agricultural soil using the ACBM was 13% lower than estimates made using the IPCC default method

18. Estimates soil C change and direct N2O emissions from agricultural soils • Model-based system using integrated databases of information on climate, land use change and management • Basic geographic units are Soil Landscapes of Canada (SLC) polygons • CENTURY based estimates showed an overall CO2 loss of 7.08 Mt. in 1990, and a net sink of 0.5 Mt in 2002 Canada National C and Greenhouse gas emission Accounting and Verification System for agriculture (NCGAVS)

19. Germany • Using two dynamic models for estimating NO and N2O emissions - Denitrification and Decomposition (DNDC) model (for agricultural soils) - Photosynthesis and Evapotranspiration- Nitrification- Denitrification and Decomposition (PnET-N-DNDC) model (for forest soils) • Better estimates from multi-year simulations at regional scale • Consistent with IPCC default (ag soil estimates only 10% higher compared to IPCC)

20. New ZealandCarbon Monitoring System (CMS) • to estimate C stock changes due to land cover changes, based on a simple empirical model, similar in concept to the IPCC Tier 1 approach • Soil C estimated for land cover/use categories in 18 different soil-climate classes • more detailed breakdown of climate zones, and inclusion of an erosivity index compared to IPCC method • encouraging results at local site scale, but sometimes overestimated the observed soil C at regional scale, due to variation in local factors such as stoniness and slope • Major data gaps need to be filled before efficient operation

21. CMS and IPCC GPG/default soil C values (t C ha-1, top 30cm) for arable soils (Tate et al., 2002, IPCC GPG, 2003)

22. SwedenIntroductory Carbon Balance Model (ICBM) • a two pool model calibrated using long-term field data, incorporated into a regional framework to estimate changes in soil C • Conceptually simple; can be run and optimized in a conventional spreadsheet program • Input data- agricultural statistics, daily weather data, climate region, soil type, crop type, etc. • This model approach is still in the testing phase, and currently only the emissions from organic soils are reported in the NIR.

23. United States • a Tier2 versopm of the IPCC methodology with US-specific reference C stocks and stock change factors (+11 Tg for mineral soils and -9 Tg for organic soils) • Dynamic approach using CENTURY model (+23 Tg for mineral soils) • incorporates information from National Resources Inventory (NRI) data on land use, crop type, irrigation, pasture management, soil type, etc., and tillage information • For estimating N2O emissions, a simulation based approach using the DAYCENT model is being developed. • DayCent estimates are about 10% lower than those with IPCC default method

26. Conclusions • Currently, less comprehensive reporting of GHG emissions and methods for soils • IPCC default methodology still mostly being used- simple with default emission and stock change factors • Country-specific methods, usually process-based models, are being rapidly developed in several Annex1 countries. • Simulation models with detailed activity data are used in most country-specific methods. • One constraint for fully utilization of country-specific methods is the lack of comprehensive national databases.

27. Acknowledgements • National Greenhouse Offices • Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS) for financial support