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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