dndc model
DESCRIPTION
Publication from the Sustainable Food LabTRANSCRIPT
Energy and GHG Webinar:DNDC Model
June 23, 2009
Dr. William SalasApplied Geosolutions, LLC
87 Packers Falls RoadDurham, NH 03924 USA
Dr. Changsheng LiComplex Systems Res
University of NewDurham, NH 03924 USA
earch Center Hampshire
APPLIED GEOSOLUTIONS, LLC
Webinar Outline:What are process based models?DNDC Modeling frameworkManure-DNDC modeling framework Role of DNDC for C accounting and ag offsetsExample Application (tomato)DNDC demonstration for CA Rice production
Why do we need Process Models?
Figure Source: Guo, ARB
What are Process-based Models?Process-based modeling refers to biochemical and geochemical reactions or processes
Process modeling, in this case, does not refer to AFO practices or components (e.g. dairy drylots or manure lagoons) per se, but
Biogeochemical processes… like decomposition, hydrolysis, nitrification, denitrification, etc…True process-based models do not rely on constant emission factors. They simulate and track the impact on emissions of varying environmental and management conditions and drivers.
Example Process-based Models
Daycent ModelDaily time step version of the CENTURY ecosystem model (developed for soil carbon dynamics)Developed by CSU and ARSWebinar last week.
DNDC ModelDNDC stands for Denitrification and Decomposition, two processes dominating losses of N and C from soil into the atmosphere, respectivelyInitially developed for field level N2O emissions
DNDC and DAYCENT Models
Two of the leading N2O process models for agricultural systemsDNDC and Daycent share a lot in common in modeling approach: (1) plant growth, (2) soil climate and (3) soil organic matter turnover However, they differ in approach for trace gas (e.g. N2O) emissions.
DNDC: soil Eh and microbial population dynamics Daycent: leaky pipe approach (% of N mineralization subject to soil environment conditions)
DNDC resulted from a 20-year international effort with researchers from the U.S., China, Germany, the U.K., Canada, Australia, New Zealand, the Netherlands, Belgium, Finland, Japan and India.
The DNDC Modelecologicaldrivers
Climate Soil Vegetation Human activity
soil environmentalfactors
Temperature Moisture pH Substrates: NH4+, NO3
-, DOCEh
Denitrification Nitrification Fermentation
Decomposition
Plant growth
Soil climate
NH4+
clay-NH4
+NH3
DOC nitrifiers
NO3-
N2O NO NH3
DOC
NO3-
NO
N2O
N2
NO2-
nitrate denitrifier
nitrite denitrifier
N2O denitrifier
CH4CH4 production
CH4 oxidation
CH4 transport
soil Eh
aerenchyma
DOC
soil tempprofile
soil moistprofile
soil Ehprofile
O2diffusion
O2 use
verticalwaterflow
very labile labile resistant
litter
labile resistant
labile resistant
microbes
humads
passive humus
CO2
DOC
NH4+
roots
stems
grain
N-demand
N-uptake
water demand
water uptake
water stress
daily growth
root respiration
potentialevapotrans.
LAI-regulatedalbedo evap. trans.
effect of temperature and moisture on decomposition
annual averagetemp.
DOC
Electron acceptor
O2
NO3
Org-C
CO2 N2O CH4
Eh
DNDC Trace Gas Approach:
Farming practices affect GHG emissions through…
Tillage
Fertilization
Manure use
Irrigation
Crop rotation
Soil reclamation
Micro-meteorology
DNDC bridges between ecological drivers and GHG emissions
INPUTINPUTINPUT PROCESSES OUTPUT
Climate- Temperature- Precipitation - N deposition
Soil properties- Texture- Organic matter- Bulk density- pH
Management- Crop rotation- Tillage- Fertilization- Manure use- Irrigation- Grazing
DNDC
1. Soil water movement2. Plant-soil C dynamics3. N transformation
Availability of water, NH4, NO3, and DOC
Used by soil microbes
Used byplants
Emissions of N2O, NO, N2, CH4 and CO2
Growth of cropbiomass
Competition N leaching, NH3 emissions
Model Validation…Rigorous model validation is key for acceptance (scientific and market)Lack of appropriate field data for process-model validationDNDC has been validated extensively for agroecosystems worldwide (over 100 peer review papers)Additional validation efforts underway (e.g. CA).
Nitrous Oxide ValidationObserved and DNDC-Modeled N2O Fluxes from Agricultural Soils in the U.S., Canada,
the U.K., Germany, New Zealand, China, Japan, and Costa Rica
0.1
1
10
100
1000
0.1 1 10 100 1000
Observed N2O flux, kg N/ha/year
Mod
eled
N2O
flux
, kg
N/h
a/ye
ar
0.4
0.
0. 0.4
0.032
0.37
0.
0.
0.033
0.05
0.037
0.340.41
0.43
0.032
0.032
0.032
0.035
0.015
0.0350.029
0.035
0.028
0.011
0.031
0.05
0.0290.029
0.006
0.01
0.0190.019
0.02 0.025 0.025
0.010.015
R2 = 0.8366
Methane ValidationObserved and DNDC-modeled CH4 fluxes from rice paddies in China, Thailand, Japan, Italy and the U.S.
R2 = 0.948
0
100
200
300
400
500
600
700
800
900
0 100 200 300 400 500 600 700 800
Modeled CH4 flux, kg C/ha/yr
Mea
sure
d C
H4
flux,
kg
C/h
a/yr
Structure of Manure-DNDCManure production Housing Storage Field application
Milk or meat production
Intake of C, N and water
Quantity and quality of fresh manure: dung
and urine
Temperature, moisture, pH, bedding and ventilation
Decomposition, hydrolysis, nitrification,
denitrification, fermentation
Emissions of CO2, NH3, CH4,
N2O, NO
Quantity and quality of manure
Aerobic storage or compost,
lagoon, slurry tank, digester
Decomposition, hydrolysis, nitrification,
denitrification, fermentation
Emissions of CO2, NH3, CH4,
N2O, NO
Quantity and quality of
residue manure
Climate, soil, farming
management
Decomposition, hydrolysis, nitrification,
denitrification, fermentation
Emissions of CO2, NH3, CH4,
N2O, NO
Soil C and N storage
Emissions of CO2, CH4, N2O,
NO
Crop Production
Nitrogen Biogeochemistry of Manure
Manure production Manure organic pools N tranformation in manure
Dung
Bedding
Urine
Very labile litter N
Labile litter N
Resistant litter N
Labile microbial N
Resistant microbial N
Labile humad N
Resistant humad N
Passive humus NNH4+
NO3-
NH3
Clay-NH4+
NO2-
NO
N2O
N2
Atmospheric N deposit or fertilization
NH3N2NO N2O
Nitrification
Denitrification
Assimilation
DecompositionLeaching
Urea
Fresh manure
Chemical equilibrium Gas emissionLitter fallHydrolysis
Atmospheric deposition and fertilization
Chemodenitrification
Create Manure-DNDC by linking farm components to DNDC
DNDC
Feeding TreatmentStorageHousing
Field application
Crop Production
PC Menu Based Tool
Menu Driven Inputs for Each Component of Manure Management
Input parameters:- Daily climate data;
- Animal type and population; Intake protein and feed quality;
- House ventilation; floor surface and bedding; cleaning method;
- Compost size, density, storage time, litter addition;
- Lagoon capacity, surface area, coverage, draining frequency;
- Slurry tank capacity, coverage, storage time;
- Anaerobic digester capacity, hydraulic retention time,CH4 production;
- Manure field application: rate, C/N, timing, depth, crop, soil.
Output parameters:- Production of urine and dung;
- Enteric CH4, N2O and CO2;
- Emissions of CH4, N2O, NH3, NO, N2 and CO2 from feeding lot, compost, lagoon, slurry tank and field;
- N leaching and uptake in field;
- Crop growth and yield;
- Milk and meat production
- Soil C sequestration.
Mass Balance Approach: Tracking Nitrogen
Gas Source Assessment: Manure-DNDC quantifies gas emissions from each component of the dairy
CH4: >80% from enteric emission
NH3: 70% from field application
N2O: 60% from field application
N2: 99% from lagoon emission
Full GHG Accounting by Component and Farm
NC Swine Mass Balance Case
Why DNDC for GHG Offset Projects?Process models are needed for rigorous site specific GHG estimation (NRC).Full GHG accounting (CO2, CH4 and N2O) from soils and manure.Detailed microbial processes in both aerobic and anaerobic environmentsWorks in both upland and wetland agricultural environmentsApplicable for crops and manure management systems…
Why DNDC for GHG Offset Projects?
Validated across a broad range of agro-ecosystems
Not perfect (it is a model), but model results are very encouraging.More validation underway to quantifying uncertainties and confidence levels
Projects funded in CA (CEC, CDFA, ARB) to collect data for DNDC model validation: including some specialty crops (e.g. wine grape, almonds, tomato and lettuce)Will have detailed understanding where the model works well…and where it doesn’t (needs further development)
Next Steps for Use of DNDC for GHG Offset Projects…
Updated Rigorous Validation Exercise across a broad range of environmental drivers (soils and climate) and agro-ecosystems (commodities and specialty crops).Statistically rigorous uncertainty estimates with confidence intervals (market driven)
Model uncertainties (model structure – recent scientific improvements warrant updated validation)Uncertainties derived from input data (trade-offs between specificity, ease of use and accuracy).
Next Steps for Use of DNDC for GHG Offset Projects…
Link with full carbon accounting LCA/LCI tools to capture direct emissions from on farm energy use (fuels, electricity, etc) and embodied (upstream) from machinery, fertilizer, pesticide, herbicide, etc production.Make tool easy to use for wide range of crops and geographic domains: NUGGET Web-based toolAre there simple /cost effective field measures that can be used to reduce model uncertainty? (e.g. soil moisture during mid-season drainage)
Regional DNDC Applications:GIS Inputs
DNDC
Crop Data•Crop type•Management regime
Soil Data•Organic matter•pH•Clay content•Bulk density
Climate Data•Precipitation•Temperature
Watershed Scale Applications:
GIS Data on Land Use
NUGGET: Web Version of DNDCNext Steps: Point and Click Web Model System
Web Forms:Default agronomic practices
Web User Interface: modify defaults
Rice Yields, BiomassMethane EmissionsNet GHG
NUGGET: Web Version of DNDC
Model Demo…
