carbon sequestration on agricultural land in wisconsin christopher kucharik ([email protected])...
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Carbon Sequestration on Agricultural Land in Wisconsin
Christopher Kucharik ([email protected])
Center for Sustainability and the Global Environment (SAGE)
The Nelson Institute for Environmental Studies
University of Wisconsin-Madison
November 12, 2008
The questions:
• What is terrestrial carbon sequestration and why is it connected to bioenergy feedstocks derived from agricultural land?
• Which land management options best promote C sequestration in agriculture?
• Can carbon sequestration on WI agricultural land mitigate C emissions?
The geographic extent of pre-settlement prairie
Croplands of North America -- 1992
Blended Census and Satellite Data
Source: Ramankutty and Foley (1999)
Changes to Ecosystem Carbon Balance
Prairie C fluxes1850-1950 Agriculture
FluxesPla
nt
inp
uts
Soil
resp
irati
on
Soil C pool
Time (centuries)
C S
tock
s
Time (decades)
C S
tock
s
Soil C pool
Pla
nt
inp
uts
Soil
resp
irati
on
What is terrestrial carbon sequestration ?
The net removal of CO2 from the atmosphere into long-lived pools of carbon.
What is terrestrial carbon sequestration ?
The net removal of CO2 from the atmosphere into long-lived pools of carbon.
Soil organic CSoil organic C
roots roots
trees
Carbon Sequestration
• Cost effective way to give us a 20 to 50 year time window to help curtail atmospheric CO2 build-up until other alternatives to fossil fuel can be developed to de-carbonize global energy
• Landowners would receive payments in the future as local utilities/companies purchase “carbon credits” to help mitigate their emissions – Local programs are only voluntary at this point
• Chicago Climate Exchange (CCX)
Most Promising Agricultural Land Management Practices
– Conservation Tillage (minimize disturbance)
– Prairie and grassland restoration• Conservation Reserve Program (CRP)
Nebraska No-till corn
WI CRP land
Corn
Conservation tillageConventional tillage
Corn Stover as a Biofuel Feedstock:Conservation tillage impacts
• 8 million mT in Wisconsin annually produced
• Provides structural stability to soil– Erosion prevention– Nutrient retention
• Increased residue reduces soil water loss and reduces soil temperatures
• Need to consider impacts to soil organic matter and productivity of cropping systems
• Participants voluntarily remove environmentally sensitive (highly erodible) land from production for 10 or 15 yr contracts
– Established in 1985 (Food Security Act); payment incentives– 36.0 million cumulative acres enrolled in US– Largest U.S. conservation program on private lands– ~534,000 acres in WI (2008); payments $50-100/ac
Conservation Reserve Program (CRP)
Perennial Grasses as Biofuel Sources: Switchgrass, Miscanthus
• Extremely productive (2-4 m high)
• Can be used for electricity, heating, cooking or transportation (think cellulosic ethanol).
• Is renewable energy that can produce no net increase in global warming
• May store large amounts of carbon in plant roots, pulling further carbon from the atmosphere.
• Produces smaller amounts of nitrogen and sulfur oxides (both sources of acid rain) when burned for electricity
Biofuel feedstocks
WI Governor’s Task Force on Global Warming Recommendations
• Agriculture Sector
– Encourage Prairie Plantings• Current CRP acreage 533,830 acres (1/25/08)• Plant grasses on currently cropped highly erodible land
– 3.1 million acres
– Promote Improved Soil Management Practices• Increase soil C storage through conservation tillage
– Preserve existing C sequestration in CRP• Avoid release of 0.8-1.9 MMT CO2 through 2028
Emerging market for Carbon
• Chicago Climate Exchange (CCX)– www.chicagoclimateexchange.com– Self-regulatory exchange; administers voluntary
legally binding pilot program for reducing and trading GHG emissions in NA
– Goals:• Proof of concept• Inform public and policy• Provide leadership/opportunities• Enhance reputations
National Farmer Union’s Carbon Credit Program(http://nfu.org/issues/environment/carbon-credits)
Potential C Sequestration: State of Wisconsin
Land use type Total
Acres
Soil CO2
sequestered (tons)
WI CO2 + CH4 Emissions
% equiv
1. Conservation Reserve Program
(rate: 1.0 mT CO2 ac-1)
533,830 533,830 0.47%
2. Highly erodible cropland converted to prairie/switchgrass
(rate: 1.0 mT CO2 ac-1)
3,100,000 3,100,000 2.71%
3. All harvested cropland managed with conservation tillage
(rate: 0.5 mT CO2 ac-1)
8,928,083 4,464,041 3.90%
4. Idle cropland / pastureland
(rate: 0.2 mT CO2 ac-1)
3,135,259 689,757 0.60%
Total 15,697,000 8,787,628 114,500,000
( 7.7%)
Units are metric tons C per year
Mitigating Automobile Emissions:Land use type Total WI Acres Sequestered
Soil C (tons)Equivalent
Automobiles1
% WI Registered Cars (2007)2
1. Conservation Reserve Program
(rate: 1.0 mT CO2 ac-1)
533,830 533,830 97,414 4.1%
2. Highly erodible cropland converted to prairie/switchgrass
(rate: 1.0 mT CO2 ac-1)
3,100,000 3,100,000 565,693 23.8%
3. All harvested cropland managed with conservation tillage
(rate: 0.5 mT CO2 ac-1)
8,928,083 4,464,041 814,606 34.2%
4. Idle cropland / pastureland
(rate: 0.2 mT CO2 ac-1)
3,135,259 689,757 126,098 5.3%
Total 15,697,000 8,787,628 1,603,811 67.5%
1CO2 emissions per automobile = 5.48 MT CO2 yr-1; EPA publication 420-F-05--004
2 Wisconsin. Dept. of Transportation; 2,377,245 total automobiles
0
20
40
60
80
100
0 5 10 15 20 25 30CRP Age (years)
Annual soil C accumulation rate (g C m
-2 yr
-1)
?
Why could this trend be happening?
UW Agronomy Ph.D. student Gregg Sanfordat GLBRC field trials in Arlington, WI
Five take home points
• Carbon credits are economic arrangements where businesses or individuals pay someone else to counterbalance their CO2 emissions.
• For farmers and other landowners, growing bioenergy crops may increase future payments for carbon sequestration also.
• Buyers beware: the C offsets you pay for may not actually exist in nature.
• C mitigation is not a silver bullet to stop global warming.
• There are still good reasons to perform the management practices carbon offsets encourage -- they support increases in bioenergy feedstocks.