the role of soil organic matter in the global carbon cycle · the role of soil organic matter in...

The Role of Soil Organic Matter in the Global Carbon

Cycle

R. LalCarbon Management and

Sequestration CenterThe Ohio State University

Columbus, Ohio 43210 USA

The Carbon Civilization

World Primary Energy Consumption, 1970-2025

1 Quad = 1.06 EJ

Energy Release by Fossil Fuel Combustion

C + O2 CO2 + 394 kJ/mole

The addiction of C civilization

Story, 2008

Price of Oil

2001 May 2008

Story, 2008

The March of Oil Price

The Energy Cost

Increase in oil price by $1/barrel means additional $7.4 billion cost to the car-driven culture of the U.S.

World Population Growth and CO2 Emissions

1

2

3

4

5

6

7

1900 1920 1940 1960 1980 2000Yea

250

280

310

340

370

400

CO

2 (pp

m)

Global population

Atmospheric carbon dioxide

Population growth and CO2emissions in China

CO2

Emissions

Population

Years

Popu

latio

n(m

illio

ns)

CO

2E

mis

sion

(Mill

ion

met

ric

ton,

Tg/

yr)

Population growth and CO2emissions in India

Population

CO2Emissions

Popu

latio

n (m

illio

ns)

Years

CO

2E

mis

sion

(Mill

ion

met

ric

ton,

Tg/

yr)

Energy Use and CO2 Emission

a. 1 MWh of energy = 0.14-0.28 Mg Cb. Total emissions:

I. Between 1850 and 2000 = 300 PgII. Between 2000 and 2100 = 950-2195 Pg

c. Rate of emission:I. 1990 = 5.5 Pg/yrII. 2100 = 20-35 Pg/yr

Global Carbon Budget

9.47.97.1TOTAL

1.81.61.6•Land Use Conversion

2.4380s

1.6370s

1.4360s

III. Fugitive CO2

IV. CO2 ppm

7.06.35.7TOTAL

0.70.70.5•Land

2.22.32.0•Ocean

4.13.33.2•Atmosphere

II. Known Sinks

7.66.35.5•Fossil Fuel Combustion

I. Sources-----------------Pg C/yr-------------------

2000’s1990’s1980’sParameter

Fossil Fuel Combustion and Atmospheric CO2

• 4 Pg of fossil C combustion = 1ppm of CO2 in the atmosphere

• Stabilization of atmospheric CO2 at 580 ppm = (580-380) x 4 = 800 Pg of C emission

• 1 Pg of SOC pool = 0.47ppm CO2 in the atmosphere

Biota560 Gt

Atmosphere780 Gt

+3.3 Gt/yr

Soils2,500 Gt

(i) SOC - 1,550 Gt(ii) SIC - 950 Gt

Ocean38,400 Gt + 2.3 Gt/yr

(i) Surface layer: 670 Gt(ii) Deep layer: 36,730 Gt(iii) Total organic: 1,000 Gt

Fossil Fuels4,130 Gt

(i) Coal: 3,510 Gt(ii) Oil: 230 Gt(iii) Gas: 140 Gt(iv) Other: 250 Gt

120 + 2.0 Gt/yr (photosynthesis)Plant respiration

60 + 1.6 Gt/yr

60 Gt/yr

7.5 Gt/yrFossil fuelcombustion

90 Gt/yr

0.6+0.2 Gt/yr(deposition)

60 Gt/yr (soil respiration)

Accelerated soil erosion

1.1+ 0.2 Gt/yr (erosion)MRT = 5Yr

MRT = 25Yr

Mean Residence Time (MRT) = 400Yr

1.6 + 0.8 Gt/yrDeforestation

MRT = 6Yr

92.3 Gt/yr

Biofuel offset?

Biotic Pool = 600 Pg

SOC Pool = 1550 PgSOC Pool = 1550 Pg

SIC Pool = 950 PgSIC Pool = 950 Pg

AnthropogenicEmissions9.4 Pg/yr

AtmosphericEnrichment4.1 Pg/yr

Geologic Pool

TerrestrialPool

Geologic Sequestration (EOR, CBM)

Fossil FuelCombustion7.5 Pg/yr

DeforestationSoil Cultivation1.9 Pg/yr

Terrestrial Sequestration

Terrestrial and Geologic Sequestration

Uses of Crop/Agricultural Residues

AgriculturalResidues

Retentionon Soil

Fodder

Fuel

Burning/BiocharIncorp-orating

Mulching(NT)

Grazing

StallFeeding

ManureManage-

ment

TraditionalFuel

ModernFuel Cellulosic

Ethanol

Co-Combustion

Managing Crop Residues for Carbon Sequestration

CarbonSequestration

With CropResidue

Management

Soil Application

Burial UnderOcean

Biofuel

Humification10-15%

Off-SettingEmissions

•Energy Cost of Transport•Erosion•Loss of Nutrients

CO2 Utilization and Recycling

Rather than treating it as a waste (garbage) to be disposed of underground or under the ocean, industrially emitted CO2 is a resource and an important raw material for:(i) chemical and biological products

(bio-economy)(ii) Photosynthetic products

(terrestrial/marine biosphere)

Terrestrial C Pool= 2860 Pg

+ 2-4 Pg C/yrSOC = 1550 PgSIC = 750 Pg

Biotic Pool = 560 Pg(-1.6 Pg yr–1)

Link between terrestrial and

atmospheric C pool

AtmosphericC pool =760 Pg

(+ 3.5 Pg yr-1)

Residence Time in Soil

Depletion of Soil Organic Matter

Decline in Productivityof Aquatic Ecosystems

Disruption inElemental Cycling

Decline inSoil Structure

Reduction in SoilFauna & Flora

Decline in BiomassInput into Soil

CrustingCompaction

Decline in MicrobialProcesses

Depletion of SoilFertility

Reduction inNPP

Increase in NonpointSource Pollution

and Hypoxiaa

Runoff andErosion

Loss of SoilBiodiversity

ElementalImbalance

Adverse Effects onPlant Growth

Decline in Quantityand Quality of

Water Resources

Soil Physical DegradationSoil Biological DegradationSoil Chemical Degradation

Decline in Soil Quality

Adverse Impacts of Depletion of Soil Organic Matter onAdverse Impacts of Depletion of Soil Organic Matter onSoil Quality Soil Quality and Ancillary Ecosystem Servicesand Ancillary Ecosystem Services

Management•Conservation Tillage•Prescribed Grazing•Integrated Nutrient Management

•High Biomass Rotations(Bioenergy Plantations)

Soil Quality•SOC•Soil Organisms•Water Holding Capacity

•Infiltration Rate•Soil Structure

Ecosystem Services•Air Quality•Water Quality•Productivity•Fewer Pollutants•Less Dust•Less Sediment•Drought and Disease Resistance

•Mitigation of climatechange

Land Use

Change

Managing soil organic matter as the key to soil, air, and water quality(Redrawn from Andrews et al., 2006)

Estimates of Global and Estimates of Global and Regional Potential of Soil C Regional Potential of Soil C

SequestrationSequestration1. World: 0.6 - 1.2 Pg C yr-1

2. USA: 144 - 432 Tg C yr-1

3. India: 40 - 50 Tg C yr-1

4. Iceland: 1.2 - 1.6 Tg C yr-1

5. Brazil: 40 - 60 Tg C yr-1

6. Western Europe: 70 - 190 Tg C yr-1

Terrestrial Carbon Sink Capacity

Prehistoric C loss = 320 Pg (Ruddiman, 2003)Loss since 1850 = 136 Pg (IPCC, 2000)Total loss = 456 Pg = 114 ppm CO2

(Boeckert, 2007)Assuming recovery of 40-50% = 45-55 ppm

(50 ppm)

Fig. 3 A schematic of the soil C dynamics upon conversion from a natural to agriculturalecosystem, and subsequent adoption of recommended management practices(RMPs). In most cases, the maximum potential equals the magnitude of historic Closs. Only in some soil-specific situations, the adoption of RMPs can increase SOCpool above that of the natural system. An example of this is acid savanna soils ofSouth America (Llanos, Cerrados) where alleviation of soil-related constraints candrastically enhance the SOC pool.

Time (Yrs)

100

80

60

40

20

0

20 40 60 80 100 120 140 160

Rel

ativ

e M

agn

itu

de

of

SO

C P

oo

l

land useconversion

subsistencefarming,

none or lowoff-farm

input, soildegradation

newequilibrium

adoption ofRMPs

soil

C s

ink

cap

acit

y

Accelerated erosion

Attainablepotential

Maximumpotential

Innovativetechnology I

Innovativetechnology II

∆X

∆YRate

Soil C Dynamics

Production Agriculture: Production Agriculture: A Success StoryA Success Story

PedospherePedosphere BiosphereBiosphere

AgronomicAgronomic

ProductionProduction

Linked Cycles in the SoilLinked Cycles in the Soil--PlantPlant--Atmosphere ContinuumAtmosphere Continuum

Carbon Cycle

Water Cycle

Nitrogen Cycle

Atmosphere

Soil

KEY PROCESSESKEY PROCESSES

PhotosynthesisPhotosynthesis PrecipitationPrecipitation FixationFixationRespirationRespiration EvapotranspirationEvapotranspiration MineralizationMineralizationBiomass DecompositionsBiomass Decompositions InfiltrationInfiltration DecompositionDecompositionHumus FormationHumus Formation RunoffRunoff Leaching LossLeaching Loss

(SSSA, 1992)(SSSA, 1992)

Linked Cycles in the SoilLinked Cycles in the Soil--PlantPlant--Atmosphere Atmosphere

ContinuumContinuum

Carbon Cycle

Water Cycle

Nitrogen Cycle

Atmosphere

Soil

KEY PROCESSESKEY PROCESSES

PhotosynthesisPhotosynthesis PrecipitationPrecipitation FixationFixationRespirationRespiration EvapotranspirationEvapotranspiration MineralizationMineralizationBiomass DecompositionsBiomass Decompositions InfiltrationInfiltration DecompositionDecompositionHumus FormationHumus Formation RunoffRunoff Leaching LossLeaching Loss

(SSSA, 1992)(SSSA, 1992)

Strategies for Soil C SequestrationStrategies for Soil C Sequestration

Baseline

ResidenceAnalysis

Life CycleAnalysis

CoupledCycling

DepthDistribution

Measurement& Monitoring

SoilAggregation

RootTurnover

Humification

Illuviation

Processes

MulchFarming

No-till

INM

Water/SoilConservation

CoverCropping

ComplexSystems

Practices

Soil CarbonSequestration

SoilQuality

NutrientCycling

MicrobialProcesses

NPP

Impact

Recommended Agricultural Practices and Soil Carbon

0.05-0.10Water table management/irrigation0.20-0.30Organic amendments0.05-0.10Use of improved varieties0.05-0.20Forages based rotation0.05-0.20Elimination of summer fallow0.05-0.10Soil fertility management0.05-0.20Winter cover crop0.10-0.40Conservation tillage

C sequestration potential (Mg C/ha/yr)

Recommended practices

Lal et al., 1998 CCX=500 lbs CO2/acre/yr

Rates of Soil C Sequestration in Ohio

• No-Till Farming = 300-500 kgC/ha/yr• NT + Cover Cropping = 500-800 kgC/ha/yr• NT+CC+Manure = 800-1200 kgC/ha/yr

U. S. Millennium Goals (2015)1. Eradicate extreme poverty and hunger2. Achieve universal primary education3. Promote gender equality and empower women4. Reduce child health5. Improve maternal health6. Combat HIV/AIDS, malaria and other diseases7. Ensure environmental sustainability8. Develop a global partnership for development

VersusFood Fuel

Converting corn grains and soybeansinto biofuel is creating competition between1 billion hungry stomachs and car tanks

Crop yield and productivity effects of SOC pool

SOC Pool

Cro

p Yi

eld Unfertilized

Fertilized

SOC Pool

∆Yi

eld

U.S. and Global Energy Needs

• 1 Quad = 1015 BTU• Current U.S. Energy Consumption = 100 Quads/yr• Projected Increase in Demand = 1.5%/yr in the

U.S.• World Energy Consumption = 400 Quads/yr• Projected Increase in Demand = 2.5%/yr

Biofuels From Crop Residue• Modern agriculture can generate = 10 Mg/ha of biomass• Biomass energy value = 16x106BTU/Mg• Tal cereal residue produced in the U.S. = 350 Tg/yr• Gross biofuel energy value of residues = 6 Quads/yr• Net energy value = 3 Quads/yr• Energy Value of 33% of the residue = 1 Quad/yr

Energy conservation can save upto 30% of energy use

One Billion Ton CellulosicFeedstock

• The goal is to produce 1 billion ton of lignocellulosic feedstock

• 2030 vision: 30% biofuel by 2030

Rates of Corn Stover Retention and Soil Properties at Coshocton, OH

0.970.92

0.920.710.970.93

Y= 1.7x + 2.6Y= -0.06 x2 + 0.9x - 0.02

Y= 0.003x2 - 0.05x + 1.42Y= -0.11x2 - 1.57x + 15.14Y= -0.81x2 + 14.4x + 235Y= -0.06x2 + 0.9x + 9.6

Middens (#/m2)

Hydraulic conductivity (mm/h)Bulk density (g/cm3)Organic Carbon (Mg/ha)Corn Height (cm)Grain yield (t/ha)

R2Regression equation

Soil Property/yield

Blanco-Canqui, Lal and Owen (2006).

Biofuel From Industrial CO2 and SOC Sequestration

Ethanol

Biodiesel

Biochemicals

Nutrient-Enriched &

Biochar/Compost

Residues

Bioreactors

Soil Carbon Sequestration

Algae

Cynobacteria

Algae

Cynobacteria

App

licat

ion

on A

g. S

oils

Bioenergy

Cellulosic ethanol

Sugar Fermentation

CO2 evolution

Decomposition of lignin and cellulose

Conversion of starch to sugar

Grain-basedethanol

Ecological Footprints of Crop Residues Removal for Biofuel Production

Microbial Processes

Energy Efficiency vs. Residue Removal

• Meeting 1% of energy needs can seriously jeopardize nations/world soil and water resources

• Improving energy use efficiency can reduce demand by 20-30%

Carbon Debt Upon Conversion of Native Ecosystems to Biofuel Plantations (Fargione et al., 2008)

No debt2.1100000Prairie Biomass Ethanol

Marginal Cropland

11.21002-2Corn EthanolAbandoned Cropland

480.338319118Corn EthanolAbandoned Cropland

930.338337334Corn EthanolCentral Grassland

370.253923122Soybean BiodieselCerradoWoodland

172.7100451431Sugarcane Ethanol

CerradoWooded

3190.253920013565Soybean BiodieselTropical Rainforest

4231.987353135218Palm BiodieselPeatlandRainforest

861.98719013555Palm BiodieselTropical Rainforest

Time to Repay C Debt (yr)

Annual Payment (Mg C/ha/yr)

Debt Allocated to Biofuel (%)

Carbon Debt (Mg C/ha)

BiofuelFormer Ecosystem

Soil Biomass Total

Economist, 2007

1850 1900 50 20070

50010001500

2000

100

The Economist $ food index1845-50-100

Estimates of Under-Nourished People (FAO, 2006)

96.1820Developing Countries100854TOTAL1.19Industrialized Countries1.19Transition Countries4.438Near East/North Africa6.152Latin America/Caribbean17.6150China19.0162Asia/Pacific24.1206Sub-Saharan Africa24.8212India

% of TotalPopulation (106)

Region

Estimates of Under-Nourished People (FAO, 2006)

26%

25%19%

18%

6%

4%

1%

1%

India

SSA

Asia/Pacific

China

LatinAmerica/CaribbeanNear East/NorthAfricaTransition Countries

IndustrializedCountries

Mean Crop Yield in India, Kenya and Developed Countries (FAO, 2005)

79808141026Chickpea1790332730Cowpea39107971455Sorghum834019072006Maize311026011469Wheat681032841872Rice

Developed Countries

IndiaEthiopiaYield (kg/ha)Crop

Areas where current population exceeds potential agricultural capacity

Economics of Residue Removal for Biofuel

Estimated Increase in Food Production in Africa by Increase in SOC Pool by

1 Mg C/ha/yr (Lal, 2006)

6.3 - 11.6Total

3.0 - 6.2Roots and Tubers

3.3 - 5.4Grains

Total Annual Increase (106 Mg/yr)Type

Commodification of soil C

How can soil C be made a commodity that can be traded like any other farm product?

The value of soil carbon

• Value to farmer: for soil quality enhancement

• Value to society: for ecosystem services

Societal value of soil carbon

• Reduction in erosion and sedimentation of water bodies.

• Improvement in water quality.• Biodegradation of pollutants.• Mitigation of climate change.

On-farm value of soil carbon

• The quantity of NPK, Zn, Cu etc. and H2O retention in humus.

• Improvements in soil structure and tilth.• Decrease in losses due to runoff, leaching and

erosion.~ $200/ton

Need for determining a just value of soil carbon

• Under valuing a resource can lead to its abuse.

• It is important to identify criteria for determining the societal value of soil C, and using it for trading purposes.

Trading C Credits

The C market may reach $ trillion by 2020. We need to make this market accessible to land managers.

Trading Carbon

Tragedy of Crop RemovalTragedy of Crop Removal

Indiscriminate removal of crop residue is taking soil for granted and treating it as dirt.

Why is this so?

Taking Soils for Granted

Is it because:• We are seduced by the short-term economic

gains?• Our knowledge of soil processes is fragmentary

and distorted?• We forget history (e.g., The Dust Bowl)?• We are desperate about the energy needs? and• We are not cognizant of the basic laws of

ecology?

Four Laws of EcologyFour Laws of Ecology1. Everything is connected to

everything else.2. Everything must go somewhere.3. Nature knows best.4. There is no such thing as a free

lunch.. . . Barry Commoner

(1971)

Soil and Survival

“Upon this handful of soil our survival depends. Husband it and it will grow our food, our fuel, and our shelter and surround us with beauty. Abuse it and the soil will collapse and die, taking humanity with it”.

From VedasSanskrit Scripture 1500 BC

The Balancing Act

“We may utilize the gifts of Nature just as we choose, but in Her books, the debits are always equal to the credits.”

…M.K. Gandhi