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Tools for quantifying GHG emissions Tools for quantifying GHG emissions from Agroecosystemsfrom Agroecosystems
E. Pattey, R.L. Desjardins and W. Smith
Agriculture and Agri-Food Canada, Research Branch, Ottawa
CAgM Expert Team Meeting on the Contribution of Agriculture to the State of Climate
Ottawa, Canada, 27 - 30 September 2004
INTRODUCTIONINTRODUCTION
Goals:
Develop a set of reliable Models for estimating net GHG emissions from agricultural sources/sinks and for deriving emissions factors relevant of a given country situation.
Establish a series of databases of the various agricultural activities for integrating the GHG emissions over space and time domains (land use, mgt practices, animal production, climate…) .
INTRODUCTION (Cont’d)INTRODUCTION (Cont’d)
A “reliable” Model is:sensitive to input conditions such as management practices;adapted to the geographical and climatic conditions under which it will be used;based on sound scientific knowledge.…Ideally it requires a set of input descriptors easily available.
Framework:
Any national GHG emission accounting system needs to be transparent (well-documented), verifiable (pilot test sites, scaling-up experiments etc.) and consistent with the Kyoto Protocol.
OUTLINEOUTLINE
•Speaker more familiar with Canadian situation Example of Canada…
•GHG emission estimates from agricultural sources in Canada, CO2, CH4, N2O
•Tools for developing models (chamber, tower)
•Tools for verifying temporal dynamic and top-down constraints (tower, aircraft)
•Results from tower- aircraft-based measuring systems
•Modeling results from Ecosys, DNDC and Daycent
•Summary
Greenhouse Gas Emissions from Greenhouse Gas Emissions from Canada’s Agroecosystems Canada’s Agroecosystems
(100 Year Time Horizon - Tg of CO(100 Year Time Horizon - Tg of CO22 equivalents) equivalents)
CO2 8 7 5 2CH4 22 19 20 23N2O 27 30 28 38
1981 1986 1991 1996 2001
02440
Total 57 56 53 63 64
GHG flux measuring techniques only cover a limited portion GHG flux measuring techniques only cover a limited portion of the space and time domainsof the space and time domains
Aircraft
Atmospheric Inversion
Tower
Chamber
1 102 105 104 103
1
103
104
102
10
Area m2
Time h
Soil Cores
Mass Balance
10 107 106
BLS&
Tracer
109 108
Regional and sub-continental estimates using tall towers and
CBL budgets
Satellite
Au
dit
ing/
Mon
itor
i ng
Long Term Experimental Sites: Flux, Meteorological and Ancillary
MeasurementsFGHG
Regional/ National
Estimates
Regional (Spatial)databases
“Ecosystem Models”
Benchmark Sites Inventory/ Monitoring Sites
Cs
Regional Flux and Surface FeatureMeasurements
Process Studies
•climate•soils•topography•land use•land management
Data collection
Driving variables
VerificationVerification
Research Needs
Model Refinement
Scaling Up
Verification
Model Refinement
Proposed Framework for a Accounting/Verification System
How do we improve and verify models?How do we improve and verify models?
ModelingModeling ModelingModeling
Measuring Measuring chambers, chambers,
towerstowers
Measuring Measuring chambers, chambers,
towerstowers
Virtual FarmVirtual Farm(with uncertainty (with uncertainty
estimates)estimates)
Virtual FarmVirtual Farm(with uncertainty (with uncertainty
estimates)estimates)
timetimetimetime
Verifying Verifying temporal temporal dynamicdynamic
Verifying Verifying temporal temporal dynamicdynamic
Top-Down Top-Down constraintconstraintTop-Down Top-Down constraintconstraint Regional & Regional &
Nat’l GHG Nat’l GHG budgetbudget
(with uncertainty (with uncertainty
estimates)estimates)
Regional & Regional & Nat’l GHG Nat’l GHG
budgetbudget(with uncertainty (with uncertainty
estimates)estimates)
Measuring Measuring towers, blimps towers, blimps
aircraftaircraft
Measuring Measuring towers, blimps towers, blimps
aircraftaircraft
Developing new knowledge Developing new knowledge on mgt practiceson mgt practices
Developing new knowledge Developing new knowledge on mgt practiceson mgt practices
Fg = dC V Mw
dt A Mv
Non-Flow Through, Non-Steady State Non-Flow Through, Non-Steady State Chamber MeasurementsChamber Measurements
Experimental design for comparing management practices and environmental conditions
Experimental design for comparing management practices and environmental conditions
Tower-based MeasurementsTower-based Measurements
Closed-path Tunable Diode Laser
Air Intakes
zKF g
g
Sonic anemometer
Setup for quantifying NSetup for quantifying N22O fluxes for two management practicesO fluxes for two management practices
1 TDL connected to 2 micromet. towers
145 150 155 160 165 170 175 180 185 1900.0
0.5
1.0
1.5
2.0
2.5
Fig. 4
15.5 g N m -2
9.9 g N m -2
N2O
Flu
x (
mg
N m
-2 h
-1)
Day of Year
ECOSYS
Grant, R. and Pattey, E., 2003. Modelling variability in N2O emissions from fertilized agricultural fields. Soil
Biology and Biochemistry:35(2): 225-243.
Urea applied at the following rates:0.218 0.254
0.120 0.120
Meas. model
Non-linear increase of N2O emissions with fertilizer application rate
Flux Towers are the only suitable measuring approach …Flux Towers are the only suitable measuring approach …during Snow meltduring Snow melt ( (Permanent Site, Ottawa)Permanent Site, Ottawa)
Harvested corn field - Snow meltHarvested corn field - Snow melt
The global Fluxnetglobal Fluxnet project features towers tracking the movement of carbon dioxide between various ecosystems and the air with emphasis on forest
Ameriflux
Euroflux
Japanflux
Establish a network of towers for measuring N2O fluxes to verify temporal dynamics of models and assist in scaling up from individual agricultural fields to region
Biocap
Aircraft-Based Measurements
The REA sampling system and TDL Laser
Vent (Dead band)
PTFESample Bag
DC Power supply
3-wayValve
Mass-FlowController
2-mFilter
Reliefvalve
DiaphragmPump 12 l/min
Inlet
UP
DOWN
¼” PTFEtubing
Aircraft REA system
LaboratoryTDL Laser
Canada
Casselman Flight Track
Morewood Flight Track
0 5 10 15 km
Tower Site
AC/Tower Study Sites, Spring 2001, 2003 and 2004
Casselman Flight Track
12 km
13km
Casselman
Highway 417
N
soy
cereals
pasture/grass
alfalfa
forest
corn
town
LEGEND
Morewood Flight Track
N
Mean Crop Cover in 2000 within Footprint of Aircraft Transects
0
5
10
15
20
25
30
Hay Alfalfa Corn Soybean Forest Pasture Cereals
Per
cen
tag
e (%
)
Casselman
Morewood
Aircraft Results, 2001
-10
0
10
20
30
40
50
60
70
80
90
100
15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun
N2O
Em
issi
on
s (n
g N
2O-N
m-2
s-1
)
Casselman
Morewood
-10
0
10
20
30
40
50
60
70
80
90
100
15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun
N2O
Em
issi
on
s (n
g N
2O-N
m-2
s-1
)
Casselman
Morewood
Combining Tower and Aircraft N2O Fluxes
FN2O by ACkg N2O-N
ha day
FN2O by Towerkg N2O-N
ha day
FN2O by AC (1130 to 1430)
ng N2O-N
m2 s
FN2O by Tower (1130 to 1430)
ng N2O-N
m2 s
=
Unknown
Tower and Aircraft Results, 2004
-50
0
50
100
150
200
250
300
350
400
15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun
N2O
Em
issi
on
s (g
N2O
-N h
a-1)
CasselmanMorewoodTower
-50
0
50
100
150
200
250
300
350
400
15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun
N2O
Em
issi
on
s (g
N2O
-N h
a-1)
CasselmanMorewoodTower
Modeling and Aircraft Results, 2004
0
20
40
60
80
100
120
140
160
180
200
15-Mar 22-Mar 29-Mar 5-Apr 12-Apr 19-Apr 26-Apr 3-May 10-May 17-May 24-May 31-May 7-Jun
Date
N2O
Em
issi
on
s (g
N2O
-N h
a-1)
Observed
DNDC
DayCent
Cummulative N2O-N Emissions
Interpolated Data (Mar 29 - Jun 4)
Observed 1.17 kg N2O-N ha-1
DNDC 1.80 kg N2O-N ha-1
DayCent 1.32 kg N2O-N ha-1
Exact Comparison
Observed 0.35 kg N2O-N ha-1
DNDC 0.65 kg N2O-N ha-1
DayCent 0.36 kg N2O-N ha-1
Estimated Nitrous Oxide emissions for two process based models (DNDC, DayCent) at Casselman Ontario for the year 2004
0
20
40
60
80
100
120
140
160
180
200
15-Mar 22-Mar 29-Mar 5-Apr 12-Apr 19-Apr 26-Apr 3-May 10-May 17-May 24-May 31-May 7-Jun
Date
N2O
Em
issi
on
s (g
N2O
-N h
a-1)
Observed
DNDC
DayCent
Cummulative N2O-N Emissions
Interpolated Data (Mar 29 - Jun 4)
Observed 1.17 kg N2O-N ha-1
DNDC 1.80 kg N2O-N ha-1
DayCent 1.32 kg N2O-N ha-1
Exact Comparison
Observed 0.35 kg N2O-N ha-1
DNDC 0.65 kg N2O-N ha-1
DayCent 0.36 kg N2O-N ha-1
Estimated Nitrous Oxide emissions for two process based models (DNDC, DayCent) at Casselman Ontario for the year 2004
Ecological drivers
Climate Soil VegetationAnthropogenic
activity
DecompositionCrop Growth
Soil Climate
Soil environmental factors
Temperature Moisture pHAnaerobic
balloonSubstrates
(NH4+, NO3- and DOC)
Denitrification Nitrification
N Gas Emissions Fluxes of NO, N2O, N2 and NH3
Exchange of NO and N2O
Effect of temperature and moisture on decomposition
Schematic of the major components of the DNDC model
Using models for obtaining regional and national estimates
ModelingModeling ModelingModeling
timetimetimetime
Regional & Regional & Nat’l GHG Nat’l GHG
budgetbudget(with uncertainty (with uncertainty
estimates)estimates)
Regional & Regional & Nat’l GHG Nat’l GHG
budgetbudget(with uncertainty (with uncertainty
estimates)estimates)
MeasuringMeasuringMeasuringMeasuring
0 20 40 60 80 1000
1
2
3
4
5
Time (years)
Cu
mu
lati
ve C
(T h
a-1)
Cumulative CO2-C from N fertilizer (50 kg N ha-1)
Soil C gain
Net gain
Challenge: The net impact of management practices changes with time
timetime
Cu
mu
lati
ve n
et
Cu
mu
lati
ve n
et
GH
G e
mis
sio
ns
GH
G e
mis
sio
ns
00
Option AOption A
Option BOption B
Option COption C
Option AOption A
0
10
20
30
40
50
60
70
80
90
1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998
Year
Gg
N2O
-N
Estimated direct annual N2O-N emissions
Estimated direct spring N2O-N emissions
Estimated Direct N2O-N Emissions from Agriculture Soils in Canada Using DNDC
(1970-1999)
“Model”
province
region
SLC polygon
“Situations” defined by:
• Soil• Climate• Land use• Management
National C and GHG Accounting and National C and GHG Accounting and Verification SystemVerification System
country
SOC & GHGEmissions for each“situation”
Verification by direct measurement of national GHG Verification by direct measurement of national GHG estimates best done through holistic top-down estimates best done through holistic top-down national, continental, or global scale GHG budgetsnational, continental, or global scale GHG budgets
N2O emissions?
Scientific uncertaintyScientific uncertainty
CH4 N2O
GH
G e
mis
sio
n (
Mt
CO
2 e
qu
iv.
per
year)
-40
-20
0
20
40
60
80
CO2
Relativeuncertainty(estimated)
Scientific uncertaintyScientific uncertaintyUncertainty
Uncertainty
UnderstandingUnderstanding00
Tools to quantify uncertainties
•Sensitivity tests of models
•Monte-Carlo approach for evaluating uncertainty
•Sensitivity tests of models
•Monte-Carlo approach for evaluating uncertainty
SummarySummary
•Tools for measuring GHG fluxes only cover a limited
portion of the space and time domains
•The combination of tower and aircraft-based GHG
flux measurements provide valuable information to
estimate regional fluxes on a daily basis
•Models are essential for deriving national estimates
of GHG emissions
•Models still require lots of verification and
improvement to provide more accurate estimates
•Tools for measuring GHG fluxes only cover a limited
portion of the space and time domains
•The combination of tower and aircraft-based GHG
flux measurements provide valuable information to
estimate regional fluxes on a daily basis
•Models are essential for deriving national estimates
of GHG emissions
•Models still require lots of verification and
improvement to provide more accurate estimates