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

Inventorying Agricultural Soil Greenhouse Gas Emissions:

Methods Used by Annex 1 Countries

Erandi Lokupitiya and Keith Paustian

Colorado State University

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

Major GHG sectors under the UNFCCC/Kyoto Protocol

Energy

Waste

Industrial processes Solvent and other product use

Agriculture Land-Use Change and forestry

Source/sink categories under the agricultural sector

Enteric fermentation

Manure management

Rice cultivation

Agricultural soils

Prescribed burning of savannas

Burning of agricultural residues

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

IPCC inventory methodology contd..

Estimation of N2O emissions from agricultural soils

1) 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)

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

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

Agricultural soil emissions as a percentage of total N2O emissions by Annex 1 countries

0.52

0.54

0.56

0.58

0.60

0.62

90' 91' 92' 93' 94' 95' 96' 97' 98' 99' 00'

year

% a

g so

il N

2O/ t

otal

N2O

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

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 managementD= Duration (default is 20 years).

IPCC inventory methodology contd..

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

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

Country specific methods developed by certain Annex1 countries

AustraliaNational Carbon Accounting System

(NCAS)• A model-based accounting system, based on resource

inventories, field studies, remote sensing and 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

Results from NCAS

Source: Australian Greenhouse Office

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

CanadaNational C and Greenhouse gas emission Accounting and Verification System for agriculture (NCGAVS)

• 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

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)

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

IPCC soil/ climate IPCC CMS HCA/ Cold temp dry 50 67 HCA/ Cold temp moist 95 84 Aquic 87 82 Volcanic 70-130 99

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

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.

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

Percentage of countries estimating N2O emissions

0

20

40

60

T1 T2 NR/NO

Method used

Per

cen

t co

un

trie

s percent countries

Percentage of countries estimating CO2 emissions

0

20

40

60

80

100

T1 T2 T3 NR/NO

Method used

pe

rce

nt

co

un

trie

s

mineral

organic

liming

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.

Acknowledgements

• National Greenhouse Offices• Consortium for Agricultural Soils Mitigation of

Greenhouse Gases (CASMGS) for financial support