The Science of Farm EmissionsMethane & Nitrous Oxide
Richard EckardAssociate Professor, The University of Melbourne
& Department of Primary Industries
Sectoral Greenhouse Gas Emissions Australia 2006
DCC 2008
Methane
Nitrous oxide
DCC 2008
Agricultural Greenhouse Gas Emissions 2006
• Agriculture – 58% of all methane
– 81% of all nitrous oxide
• Enteric Methane– 10.8% of National emissions
• Nitrous Oxide from soils – 2.8% of National emissions
Methane and Nitrous Oxide sources
Typical Farm Emissions
Dairy3 - 7 t CO2e/cow4 – 45 t CO2e/ha
Beef2 t CO2e/steer2 – 3 t CO2e/ha
Grains 0.2 - 1 t CO2e/ha
CH4 - Enteric74%
CH4 - Effluent ponds
1%
N2O - Effluent ponds
0%
N2O - N Fertiliser
4%
N2O - Indirect11%
N2O - Dung, Urine & Spread
10%
CH4 -Enteric82%
N2O - N Fertiliser
0%
N2O -Indirect
6%
N2O - Dung, Urine12%
CH4 -Burning
27%
N2O -Burning
17%N2O - N Fertiliser
30%
N2O -Indirect
26%
Carbon Pollution Reduction Scheme
• Agricultural emissions– Start by 2015, decision by 2013– If not in CPRS, other policies will be considered
• 16% of national account cannot be ignored• Other polices could provide less flexibility
• Either way– We will face some incentive to reduce emissions
on-farm
Enteric Methane Emissions• Produced by methanogens in rumen
– Anaerobic microbes of the Archaea Domain• Use H2 to reduce CO2 to form CH4
– >90% breathed or eructated
• Shorter lifetime in atmosphere & high GWP– 21 x CO2
• A significant loss of energy– 6 to 10% of energy intake lost as methane
Animal Class Methane (kg/year) Equivalent grazing days of energy lost per animal
Potential km driven in 6-cylinder LPG car
Mature ewe 10 to 13 41 to 53 90 to 116
Beef steer 50 to 90 32 to 57 450 to 800
Dairy cow 90 to 146 24 to 38 800 to 1350Eckard 2006
8
Methane MeasurementMethane from Individual animals in the field using SF6 Tracer
Permeation tubes
Evacuated Yolk
Grainger et al. 2007
9
Methane MeasurementPrecise Methane from Individual Animals -
Chambers/Calorimeters
Grainger et al. 2007
10
Wind
Reflector
Reflector
Laser
Methane MeasurementMethane from herds in the field - Open Path Laser & FTIR
Griffiths et al. 2007
Enteric Methane Potential Abatement Options
Management 10-15%
Rumen Manipulation & Ecology
20-30%
Diet Manipulation
10-30%
Rumen pH, Starch Forage ProcessingFeed Conversion
Efficiency (NFI)
Pasture & Grazing Management
Feed Additives
Fats & Oils
SyntheticChemicalsProbiotics
Animal numbers
Forage quality
Alternative livestock systems
Efficiency
Biological Control
Vaccination
Bacteriocins, Archaeal Viruses, Fungal Pathogens
Antibiotics
Ionophores eg. Monensin
Defaunation (eg. Ciliate protozoa)
Eckard 2002
Microbial Innoculants
eg. Acetogens
Breeding 10-30%
Plant Breeding
Genomics
Enzymes
Plant Secondary Compounds
Tannin & Saponin
Methane Abatement OptionsAnimal Management
• Reducing unproductive animal numbers– Extended lactation in dairy– Earlier finishing of beef
• 10-15% less methane
Grainger et al. 2008Wilson & Edwards 2008
Methane Abatement Options Animal Breeding
• Heritability– Methanogenesis (15%)
• Conflicts with breeding objectives?
– Net Feed Intake (13%)• Compatible with efficiency gains
– Angus, Vasse, WA– Dairy cattle, Ellinbank & NZ
Clark et al. 2005; Grainger et al. 2008; Hegarty et al. 2007; Waghorn et al 2006
Methane Abatement Options Dietary Supplements
• Dietary Oils (5-25%)
Beauchemin et al. 2007 Grainger et al. 2007
1% added fat = 6% less methane
Methane Abatement Options Dietary Supplements
• Tannins (10-25%)– Less
• Methane loss• Urinary N loss
– More• Dung N
• Soil retention
• Sources of Tannin– Acacia spp– Commercial beverage additives– High tannin legumes– Plant breeding
0
5
10
15
20
25
30
0
50
100
150
200
250
300
350
400
450
Control T1 T2 C T1 T2
CH
4(g
/kg
DM
I)
Ave
rage
CH
4E
mis
sion
s (g
/d)
Average CH4 Emissions (g/d) Estimated CH4 (g/kg DMI)
Waghorn et al 2006 Grainger et al. 2008
Methane Abatement Options Longer-Term Options (5 – 20 yrs)
• Biological control– Vaccination– Bacteriophages, Bacteriocins, – Archaeal Viruses, Fungal Pathogens
• Acetogenesis – Kangaroo, wallaby
• Faster gut rate of passage = acetogens• Same function as methanogens
– But produce acetate, not methane
Nitrous Oxide• Long residence time in atmosphere
• High GWP– 310 x CO2
• Denitrification– Warm, water-logged soils– Excess N in soil
• Inefficient use of nitrogen– >60% N inputs lost from grazing systems
N fertiliser
Legumes
Excreta
Mineralisation
NH4 NO3 N2
N2O
Denitrification
Technologies to reduceNitrous Oxide emissions
Animal10-50%
Soil10%
Management10-50%
ChemicalIntgerventions
Waterlogging / drainage (10%)
Physical interventions
Dietary Interventions
Nitrification inhibitor in urine
(30-60%)
Diuretics (eg. Salt)?
Urine distribution?
Tannins (59%)
Balancing Protein: Energy
(10-45%)
Irrigation?
Compaction/ pugging?
Minimum tillage (40%)
Nutrients2-13%
Inhibitor sprays(27-90% from urine)
Stand off pads / herd homes / winter
grazing (7-11%)
Rate
Source
Timing
Breeding
Feed Conversion Efficiency?
Formulation (inhibitors, polymers)
Genetic engineering of soil microbes?
Salt (5-10%)
Plant breeding eg. tannins
EffluentDe Klein & Eckard 2008
N2O MeasurementAutomatic Chambers & Micromet Systems
Automatic Chambers
Micromet system
Temporal Variability in Daily N2O Irrigated dairy pastures
Phillips et al. 2006
Rate of N on N2O EmissionsIrrigated Cotton
0
2
4
6
8
10
0 100 200 300N rate
Nitr
ou
s o
xid
e-N
(kg
/ha
) Cotton
Wheat-Vetch-CottonWheat-Cotton
Grace et al. 2007
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Autumn Winter Spring Summer
Nit
rous
Oxi
de l
oss
(kg
N/h
a)
Control Ammonium nitrate Urea
Season and N Source on N2O EmissionsDryland Pastures
Eckard et al. 2002
Nitrification Inhibitors on N2O Emissions Pastures
• 50% less N2O for 50 days mid-spring
• 25% less N2O for 25 days in mid-summer Kelly et al;. 2008
Refining N2O Emission Factors Low Rainfall Cropping
02468
101214
CC+NCC-NDD+N
N2O-N g ha-1 day-1 A
0
40
80 rainfall (mm) C
0.0
0.5
1.0
WFPS
D
0
20
40 soil temp (C) E
Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-050
10
20total Min N 0-200 mm (mg kg-1) F
0
1
2N2O-N g ha-1 day-1B
02468
101214
CC+NCC-NDD+N
N2O-N g ha-1 day-1 A
0
40
80 rainfall (mm) C
0.0
0.5
1.0
WFPS
D
0
20
40 soil temp (C) E
Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-050
10
20total Min N 0-200 mm (mg kg-1) F
0
1
2N2O-N g ha-1 day-1B
Cunderdin Rutherglen Horsham
EF (% of N) 0.02 % <0.01 % 0.14 %
Annual Loss (kg N2O-N/ha)
0.09 - 0.11 0.17 – 0.24 0.42 – 0.5
Barton et al. 2007 Barker-Reid et al. 2007 Officer et al. 2008
Managing Nitrous Oxide from Nitrogen
• Fertiliser management– Rate, Timing, Source and Placement
• Soil management– Soil structure– Stubble retention
• Fertiliser formulation– Controlled Release
– Inhibitors
• Urine– Tannins
– Protein : Energy ratios
– Spray inhibitors
Key Challenges
• Point of Obligation for CPRS– Up-stream and Down-Stream
• Fertiliser company – Coat all fertilisers at a cost
• Processor, abattoir• No incentive for on-farm action
– But lower cost
– On-Farm• Higher Transaction Costs
– 130,000 extra reporting
– No agreed method for reliable & cost-effective reporting
Key Challenges
• No low cost ‘measurement’ methods• Need agreed modelling method
– Method must allow incentive through differentiation • Is a cow a cow?
– Inventory vs on-farm models• Industries have developed DSS Tools
– Dairy, Beef, Sheep, Grains, Wine calculators– Cotton (QUT), FarmGas (AFI) and DGAS (Dairy)
• Industries have developed models & Tools– Grains – APSIM
– Dairy – DairyMod
– Beef/Sheep – GrassGro / SGS
In Conclusion• Farmers will face emissions restrictions in future
– BUT HOW?
– Less options for extensive systems
– Research may take 5 to 20 years still
• Should we be imposing new costs?– Global economic crisis
– Predicted food shortages
– Drought & climate change
• World Food Price Increases• BUT - Clearly we cannot farm in the future as we have in the past• Need on-farm technologies that deliver
– Abatement of methane and nitrous oxide
– PLUS improving profitability & resilience
– Meeting world demand & in a changing climate
www.greenhouse.unimelb.edu.au