The Societal Value of Soil Carbon Sequestration

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The Societal Value of Soil Carbon Sequestration

• Rattan Lal
• Director, Carbon Management and Sequestration
  Center
• The Ohio State University, Columbus, Ohio

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Global Climate Change

• ?T over the 20th century. 0.60.2C
• Rate of ?T increase since 1950 0.17C/decade
• Sea level rise over 20th century.. 0.1-0.2 m
• Change in precipitation.. 0.5-1/decade
• Extreme events. 2-4
• ..IPCC (2001)

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Atmospheric Concentration of Trace Gases Between
1750 and 1999
IPCC (2001)
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Global Carbon Budget
IPCC (2001)
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How Much C is in Soil?

• (i) Soil organic C 1550 Pg
• Soil inorganic C 750 Pg
• Total 2300 Pg
• (ii) Atmosphere 720 Pg
• (iii) Biota 560 Pg
• (iv) Ocean 38,000 Pg
• SOC pool 40 - 100 Mg/ha

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Soil vs. Atmospheric C

• 1 Pg (billion tonnes) of soil C 0.47 ppm of CO2

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Mean Residence Time of C in Different Pools

• The average atom of C spends about
• 5 yrs in the atmosphere,
• 10 yrs in vegetation (including trees),
• 35 yrs in soil, and
• 100 yrs in the sea.
• Residence time pool / flux
• The residence time is longer in soils of high
  latitude.

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ra
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Effects of Soil Erosion and Redistribution on
Trace Gases Emissions.
CO2
CO2
CH4 N2O
Depressed oxidation of CH4
CH4 N2O
C burial
Erosion Redistribution Depression
C burial
DOC
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Soil erosion and C emission
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1.14 x 1015 g/yr decomposition and emission to
the atmosphere
1500 x 1015 C in world soil
C sequestration
3.99 x 1015 g/yr stored within the terrestrial
ecosystem
5.7 x 1015 g/yr C displaced due to erosion
0.57 x 1015 g/yr transported to the ocean
Global soil erosion and dynamics of soil organic
carbon (Lal, 1995).
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Historic Soil C Loss

• World soils.. 66-90 Pg
• U.S. soils.. 5 Pg
• Recoverable C. 50-75
• Time horizon25-50 yrs

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The magnitude of soil C loss

• 30-40 Mg/ha
• Agricultural soils now contain lower SOC pool
  than their potential, and thus have a C sink
  capacity.

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Anthropogenic emissions (1850-2000)

• 1. Fossil fuel 270 30 Pg
• 2. Land use change 136 55 Pg
• Soil 78 12

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Soils and Global Warming

• Can we use soils and vegetation for scrubbing a
  dirty atmosphere?

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Carbon Sequestration

• It is the net removal of CO2 from the atmosphere
  into the long-lived pools of C such as vegetation
  and soil by biotic and abiotic processes.

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A New Definition of Agriculture

• It is an anthropogenic manipulation of carbon
  through uptake, fixation, emission and transfer.
• CU CF CE CT

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How to Increase Soil C

• A. Increase
• (i) density of C in the soil
• (ii) depth of C in the profile
• B. Decrease
• (i) decomposition of C
• (ii) losses due to erosion

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Increasing Density of C in Soil

• Plow No till
• Residue removed Residue return
• Bare fallow Cover crops
• Low input Judicious input (precision
  farming, IPM)
• No water control Water conservation and
• supplemental irrigation
• Fence to fence cropping Forestation/vegetation
  on
• marginal lands/CRP

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Disposition of Organic Residues
CO2
60-80
Organic residues 100 grams
3-8
10-30
3-8
Nonhumic compounds (polyuronides, acids, etc.)
Biomass (soil organisms)
Complex humic compounds
Humus 10-35
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Mulch Rate and SOC Content in Ohio

• No till
• SOC (Mg ha-1) 15.2 0.321 M R 0.68
• Plow till
• SOC (Mg ha-1) 11.9 0.266 M R 0.72

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Cover Crop and SOC Pool in a Miamian Soil in Ohio
Lal (1998)
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SOC pool in 0-30 cm depth over a 60-year period
at Coshocton, OH (Hao, Lal, Owen, 2002)
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Biofuel vs. Fossil Fuel

• 1 gallon of biofuel 0.5 gallon of oil/diesel
  saving

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Global Cooling Potential

• GCP (GWP)-1
• Conservation tillage
• Cover crops
• Nutrient management
• Soil restoration
• CRP/WRP
• Land use and afforestation

100-1000 Kg C/ha/y
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Land Use and Soil C Sequestration in the U.S.
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U.S. Emissions and Soil C Sequestration

• Total U.S. gas emissions.1500 MMTC/yr
• Emission from agricultural activities133 MMTC/yr
• Net soil C sequestration potential..332 MMTC/yr

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Agricultural Soils and Mitigation of GHE

• 1 bbl of diesel 220 L
• 1 L of diesel 0.73 Kg C
• ? 1 ton of C 1370 L of diesel 6.2 bbl of
  diesel
• C sequestration potential of ag soils 2 billion
  barrels/yr

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Potential of Global Soil C Sequestration

• 1-2 Pg C/yr or
• 24 of the total emissions by fossil fuel
  combustion.

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Is Soil C Sequestration A Free Lunch?

• Not really!
• Additional N, P, S etc. are needed for
  humification of residue C.
• There are hidden C costs of RMPs.

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Building Blocks of Humus

• C is only one of several constituents of humus.
• Other constituents are H, O, N, P, S and
  micronutrients.

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Nutrients Needed for Humification

• How much N, P and S are needed to convert residue
  into humus?
• How to adjust fertilizer use for desired
  productivity and converting residue into humus?

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Elemental Composition of Humus and Crop Residues
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Additional Nutrients Required to Convert 10,000kg
of Carbon into Humus
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Energy-based Input and C Sequestration

• 1. What is the carbon budget in relation to
• (i) Fertilizer use
• (ii) Manure application
• (iii) Tillage practices
• (iv) Irrigation
• (v) Liming of acid soils
• 2. C sequestration occurs only if output gt input.

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Hidden C costs of tillage methods
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Hidden C cost of fertilizers
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Hidden C cost of pesticides
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Hidden C cost of irrigation
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Farming Carbon

• Commodification of C (price)
• Incentives

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Societal Value of Carbon

• Nutrients and H2O contained in 1 kg of humus
  0.2
• ?Rational price 200/ton

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Undervaluing a Commodity

• Undervaluing carbon has and will perpetuate its
  misuse.

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Cumulative C sequestration (M/ha)
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0
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Time after conversion (yrs)
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Economics of C Sequestration

• Assessing economics of C by itself is not
  adequate.
• Evaluate the entire package of benefits

(i) To the farmer (ii) To the society
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Can soil C sequestration mitigate the greenhouse
effect?
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Dependency on Carbon

• Modern civilization is hooked on carbon. It needs
  rehabilitation, in a big way.

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Role of soil and biomass C in global C
management. Source The Global Energy Technology
Strategy, Battelle, Washington, D.C., 1998
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Soil C Sequestration

• It is aDevelopment challenge in the tropics and
  sub-tropics.
• Policy reform and implementation challenge in
  developed countries.

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A Bridge to the Future

• C sequestration in soil and vegetation is a
  bridge to the future.
• It buys us time while alternatives to fossil fuel
  take effect.
• It is a good thing to do, regardless of what
  happens to the climate.

It is truly a win-win strategy.