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