Rangelands and GHG Calculators

Peter R. Grace

Queensland University of Technology

Orange, NSW

19 November, 2008

Soil Carbon Sequestration

• Two principal approaches:

– Protecting ecosystems - Soil conservation

– Manage ecosystems

–Reduced tillage on croplands

–Increase inputs on degraded soils

–Convert to pasture

–Grazing management

Soil C SequestrationOverriding Influences

• Clay content

• Precipitation

• Temperature

Soil C vs CO2 v Temperature vs H2O

6% loss in topsoil C by 2100 (Grace et al, 2006)

Soil C SequestrationGrazing Systems

• No definitive information - ambiguous

• Grazed systems > Ungrazed

• Grazing stimulates

– Aboveground growth

– Belowground growth

– Plant community changes

• Just as important not to promote C loss

Global Dataset – Pasture Management

Predicted Soil C change (0-10 cm)6 t/ha pastureMudgee, NSW

1.5

1.6

1.7

1.8

1.9

2

clay clay loam sandyloam

Soil type

So

il C

(%

) 0-

10 c

m

5 yrs

10 yrs

Predicted Soil C change (0-10 cm)3 t/ha crop

Mudgee, NSW

1.5

1.6

1.7

1.8

1.9

2

clay clay loam sandyloam

Soil type

So

il C

(%

) 0-

10 c

m

5 yrs

10 yrs

Constraints to Soil C Accumulation in Grazing Systems

• Low water availability - Low biomass returns

• Low quality biomass

• High temperatures

Constraints to Claiming Credits

• Spatial variability

• Expensive to verify

• Permanence

Land Use

Soils

Potential Soil C Sequestration Rangelands (0-100 cm)

Soil type Area(Mha)

C increase (t/annum)

TotalMt C

TotalMt CO2

Calcarosol 42 0.12 5 18

Chromosol 16 0.74 12 43

Dermosol 7 0.74 5 19

Ferrosol 4 1.23 5 18

Kandosol 90 0.51 46 168

Kurosol 3 0.74 2 8

Rudosol 42 0.12 5 18

Sodosol 69 0.74 51 187

Tenosol 89 0.12 11 39

Vertosol 75 1.48 111 407

TOTAL 437 253 927*SOCRATES (Grace et al., 2006)

Actual (??) Soil C Sequestration Rangelands (0-100 cm)

Soil type Area(Mha)

C increase (t/annum)

TotalMt C

TotalMt CO2

Calcarosol 4.2 0.01 .05 .18

Chromosol 1.6 0.07 .12 .43

Dermosol 0.7 0.07 .05 .19

Ferrosol 0.4 0.12 .05 .18

Kandosol 9.0 0.05 .46 1.68

Kurosol 0.3 0.07 .02 .08

Rudosol 4.2 0.01 .05 .18

Sodosol 6.9 0.07 .51 1.87

Tenosol 8.9 0.01 .11 .39

Vertosol 7.5 0.15 1.11 4.07

TOTAL 43.7 2.53 9.3*SOCRATES (Grace et al., 2006)Methane oxidation < 1.0 Mt CO2

Main Sources of On-Farm GHGs

CH4CO2, CH4, N2O CO2

Soil type, climate and management specific

Anthropogenic Sources of Methane and Nitrous Oxide Globally

Total Impact 2.0 Pg Cequiv 1.2 Pg Cequiv

Source IPCC 2001; from Robertson 2004

(compare to fossil fuel CO2 loading = 3.3 PgC per year)

Industry Industry

Agriculturalsoils

Biomassburning

Cattle &feedlots

AgricultureAgriculture

Energy

Othercombustion

Landfills

Entericfermentation

Wastetreatment

Ricecultivation

Biomassburning

CH4 N2O

Greenhouse Gases – in brief

3 major gases = CO2, N2O, CH4

CH4 has global warming impact 23 X CO2

N2O has global warming impact 296 X CO2

CO2 equivalents

CO2e = 1 * CO2 + 23 * CH4 + 296 * N2O

Emissions Facts

1000 L diesel = 2.6 tonnes CO2

Irrigation (ca. 3 tonnes CO2/ha)

Cattle emit 60 kg CH4/yr = 1.4 tonnes CO2

Dependent on feed quality and age of cattle 1 tonne N fert emits 5 kg N2O = 1.5 t CO2

Residential electricity = 12 t CO2/annum

On-Farm GHG Emissions• Fuel:CO2

• Cultivation: CO2 • Residue decomposition : CO2 N2O• Nitrogen application: N2O• Burning crop residues: N2O CH4

• Biological N fixation: N2O• Waterlogging CH4

• Animal emissions CH4

• Urine and dung N2O• Manure management (feedlots) N2O CH4

Greenhouse Gas InventoryDarling Downs

• 416 ha total• 300 ha crop @ 84 kg N/ha• 12 ha trees• 100 head cattle

Category Source Total CO2(e)

(tonnes)Crop N2O

1 Pasture 0Dryland 8.9

Irrigated cereal 19

Irrigated cotton 7.1

Fertiliser N2O1 Direct loss 154.0

Other N2O1 Atmos. Deposit 12.2

Leaching 3.5

Dung and faeces 12.6

Soil CO2Dryland 8.2Irrigated 58.2

Fuel/power CO2Electricity 0.2Petrol 10.8

Diesel 106.4

CH4Animals 138

Sinks CO2Trees -47

TOTAL 492.5

11.25% loss

Category Source Total CO2(e)

(tonnes)Crop N2O

1 Pasture 0Dryland 8.9

Irrigated cereal 19

Irrigated cotton 7.1

Fertiliser N2O1 Direct loss 61.5

Other N2O1 Atmos. Deposit 12.2

Leaching 3.5

Dung and faeces 12.6

Soil CO2Dryland 8.2Irrigated 58.2

Fuel/power CO2Electricity 0.2Petrol 10.8

Diesel 106.4

CH4Animals 138

Sinks CO2Trees -47

TOTAL 431.5

10.5% loss

Nitrous oxide (N2O)

• Nitrogen gas emitted from added N sources

• Nitrogen fixation

• Nitrification (ammonium to nitrate)

• Denitrification (nitrate to nitrogen gases)

Portable Greenhouse Gas Monitoring

Global Greenhouse Gas Network

Reducing N2O Emissions - Benefits

• N2O reductions are

– immediate and permanent

– possible across a very wide range of crop lands and geographic areas

Greenhouse Gas Inventory

1. Soil carbon change (Gross C sequestration)

Greenhouse Gas Inventory

1. Soil carbon change (Gross C sequestration)

2. CO2 from fuel (planting, cultivation, harvesting, chemicals)

Greenhouse Gas Inventory

1. Soil carbon change (Gross C sequestration)

2. CO2 from fuel (planting, cultivation, harvesting, chemicals)

3. N2O from N fertilizer applied, N fixed and other N losses (leaching etc)

Greenhouse Gas Inventory

1. Soil carbon change (Gross C sequestration)

2. CO2 from fuel (planting, cultivation, harvesting, chemicals)

3. N2O from N fertilizer applied, and other N losses

4. N2O and CH4 from burning

Greenhouse Gas Inventory

1. Soil carbon change (Gross C sequestration)

2. CO2 from fuel (planting, cultivation, harvesting, chemicals)

3. N2O from N fertilizer applied, and other N losses

4. N2O and CH4 from burning

5. CH4 from animals

Net carbon sequestration = 1 - (2+3+4+5)

SE Australia Greenhouse Gas Assessment

Carbon Sequestration (no-till) South-East Australia (0-30 cm)

0

50

100

150

Mal

lee

Wim

mer

a

Hig

hR

ain

fall

Mid

-N

ort

h

Cen

tral

Wes

t

Slo

pes

Carbon sequestered(kg C/ha/yr)

Gross Net

Calculator website

• www.isr.qut.edu.au

Calculator website

• www.isr.qut.edu.au

Take home messages!

• High temperatures, low rainfall - difficult environment to sequester significant carbon mass

Take home messages!

• High temperatures, low rainfall - difficult environment to sequester significant carbon mass

• Rangelands and pastures may offer some benefit, but their usefulness will depend on market opportunities

Take home messages!

• High temperatures, low rainfall - difficult environment to sequester significant carbon mass

• Rangelands and pastures may offer some benefit, but their usefulness will depend on market opportunities

• Verification and transaction costs are high

Take home messages!

• High temperatures, low rainfall - difficult environment to sequester significant carbon mass

• Rangelands and pastures may offer some benefit, but their usefulness will depend on market opportunities

• Verification and transaction costs are high• Whole farming systems approach with all gases is

ESSENTIAL

Take home messages!

• High temperatures, low rainfall - difficult environment to sequester significant carbon mass

• Rangelands and pastures may offer some benefit, but their usefulness will depend on market opportunities

• Verification and transaction costs are high• Whole farming systems approach with all gases is

ESSENTIAL• Increased N use efficiency is a must for reducing

your greenhouse gas signature

Take home messages!

• High temperatures, low rainfall - difficult environment to sequester significant carbon mass

• Rangelands and pastures may offer some benefit, but their usefulness will depend on market opportunities

• Verification and transaction costs are high• Whole farming systems approach with all gases is ESSENTIAL• Increased N use efficiency is a must for reducing your greenhouse

gas signature• Maintaining soil C is key to long term productivity and

profitability

Questions?