Transcript Slide 1

Carbon implications
of different biofuel pathways
Pep Canadell
Global Carbon Project
CSIRO Marine and Atmospheric Research
Canberra, Australia
Key Messages
1.
Most biofuels on existing agricultural lands have a significant
C offset capacity (20%-80%), there are exceptions.
2.
Direct (or indirect) expansion of biofuels into forest systems
leads indisputably to net carbon emissions for 10s to 100s.
3.
Expansion of biofuels on abandoned and degraded lands
can produce net C offsets immediately or in < 10 years and
generate 8% of global current primary energy demand, an
amount most significantly in regions such as Africa.
4.
A full radiative forcing approach needs to be explored.
Life-cycle and Impacts on Climate
1. Industrial life-cycle
•
•
•
Cultivation, harvest, conversion, including fertilizers, energy requirements,
embedded C in machinery, etc. (sensitive to boundary conditions)
Co-products (easy for electricity and heat co-generation, difficult for others)
Full GHGs life cycle (CO2 equivalents)
GHG emissions reduction
Biofuels are NOT carbon neutral
Ethanol
Thow & Warhurst 2007
Biodiesel
Potential Annual C offsets (tons C/ha/year)
Gibbs et al 2008, ERL, in press
Most Studies Show Benefits from Corn Ethanol
Net GHG emissions to the atmosphere
Net GHG emissions avoided
Full GHGs: Large contribution from N2O
Global Warming Potential: 300 x CO2
Mid-range values
GHG Emissions (kg CO2equiv/GJ)
CO2
CH4
N2O
Total
Biofuel
Rape Methyl Ester
25
0.69
15
40.7
Sugarbeet Ethanol
34
0.32
5.6
39.9
Wheat Ethanol
24
0.69
3.7
28.4
Wheat straw Ethanol
Pure Rapeseed Oil
0
15
- 0.59
0.49
13.3
14.3
12.7
29.8
New inversion calculations by Paul Crutzen show that biofuels such as rapeseed
may produce large quantities of nitrous oxides, and for corn and canola it is
worse than using gasoline.
Elsaved et al 2003; Crutzen et al. 2007, ACPD
Life-cycle and Impacts on Climate
1. Industrial life-cycle
•
•
•
Cultivation, harvesting, processing including fertilizers, energy, embedded C
footprints in machinery, etc.
Co-products (easy for electricity and heat co-generation, difficult for others)
Full GHGs life cycle (CO2 equivalents)
2. Ecological life-cycle
•
•
•
•
Land use change and ecosystem carbon lost (Ecosystem Carbon Repayment
Time, ECRT)
Soil carbon sequestration
CO2 sink lost
Additional full GHGs work (N2O) emissions)
Ecosystem Carbon Payback Time (ECPT)
Number of years after conversion to biofuel production required for
cumulative biofuel GHG reductions, relative to fossil fuels they displace, to
repay the biofuel carbon debt.
Fargione et al. 2008, Science
Ecosystem Carbon Payback Time (Tropics)
Only Carbon taken into account
With current crop yields
Peatlands
918 years
Gibbs et al 2008, ERL, in press
Ecosystem Carbon Payback Time (ECPT)
Using 10% percentile global yield
Peatlands
587 years
Gibbs et al 2008, ERL, in press
Bioenergy Potential on Abandoned Ag. Lands
Abandoned
Crop
385-472 M ha
Abandoned agricultural land
%Area
4.3 tons ha-1 y-1
Area weighted mean
production of above-ground
biomass
Abandoned
Pasture
32-41 EJ
8% of current primary
energy demand
Abandoned
Agriculture
Campbell et al 2008, ESC, in press
Biofuel Crops
versusemissions
Carbon Sequestration
Cumulative
avoided
over 30 years
Cumulative avoided emissions
per hectare over 30 years for a
range of biofuels compared with
the carbon sequestered over 30
years by changing cropland to
forest
Land would sequester
2 to 9 times more
carbon over 30-years
than the emissions
avoided by the use of
biofuels
Righelato and Spracklen 2007, Science
Lost of C Sink Capacity by Deforestation
A1 SRES
Lost of biospheric C sink due to
land use change
Additional 61 ppm by 2100
Life-cycle and Impacts on Climate
1. Industrial life-cycle
•
•
•
Cultivation, harvesting, processing including fertilizers, energy, embedded C
footprints in machinery, etc.
Co-products (easy for electricity and heat co-generation, difficult for others)
Full GHGs life cycle (CO2 equivalents)
2. Ecological life-cycle
•
•
•
•
Land use change and ecosystem carbon lost (Ecosystem Carbon Repayment
Time, ECRT)
Soil carbon sequestration
CO2 sink lost
Additional full GHGs work (N2O) emissions)
3. Full radiative forcing life-cycle
•
•
All GHGs
Biophysical factors, such as reflectivity (albedo), evaporation, and surface
roughness
5. Full Radiative Forcing
Temperate
deciduous
Tropical
forest
Full Radiative
Forcing
Albedo
Roughness
Evapotranspiration
Cloud formation
Boreal
forest
Cropland
Grassland
Bruce Hungate, unpublished
Monthly Surface Albedo (MODIS)
Jackson, Randerson, Canadell et al. 2008, PNAS, submitted
Life-cycle and Impacts on Climate
1. Industrial life-cycle
•
•
•
Cultivation, harvest, conversion, including fertilizers, energy requirements,
embedded C in machinery, etc. (sensitive to boundary conditions)
Co-products (easy for electricity and heat co-generation, difficult for others)
Full GHGs life cycle (CO2 equivalents)
2. Ecological life-cycle
•
•
•
•
Shifting from GHG emissions per GJ biofuel or per v-km to emissions per ha y-1.
Land use change and ecosystem carbon lost (Ecosystem Carbon Repayment
Time, ECRT)
Soil carbon sequestration
CO2 sink lost
3. Full radiative forcing life-cycle
•
•
All GHGs
Biophysical factors, such as reflectivity (albedo), evaporation, and surface
roughness
End
• Lignocellulosic biofuels will be able to achieve
greater energy and GHGs benefits than highly
intensive crops such as corn and rapeseed
because:
– require less fertilizer
– can grow in more marginal lands
– allows for complete utilization of the biomass (which
can compensate smaller yields per ha.
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30
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25
800
20
600
15
400
10
200
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Avoided GHG Emissions (gCeq/v-km)
Avoided GHG Emissions (kgCeq/ha/yr)
Most studies focus on GHG emissio
per GJ biofuel or per v-km. Emission
per ha/yr may give different ranking.
N2O emissions depend on type of crop
(e.g., annual vs. perennial), agronomic
practices, climate, and soil type.
Direct N2O from annual crops, Germany
N2O from short-rotation willow, NE USA
GM, et al. 2002 (European study).
Heller, et al. 2003.
Mitigation Cost per ton of CO2 (Euros)
Germany
800
700
600
500
400
300
200
100
0
Wind
Hydro
Biomass
electr.
Photovoltaics
Bioethanol
Courtey of Gernot Klepper; Quelle: BMU, BMWi, DLR, meó
Biodiesel
Bioethanol
BRA
ETS
From eric larsen presnetation
Striking features of LCA studies reviewed
• Wide range of biofuels have been included in different LCAs:
– Biodiesel (fatty acid methyl ester, FAME, or fatty acid ethyl ester, FAEE)
• rapeseed (RME), soybeans (SME), sunflowers, coconuts, recycled cooking oil
– Pure plant oil
• rapeseed
– Bioethanol (E100, E85, E10, ETBE)
• grains or seeds: corn, wheat, potato
• sugar crops: sugar beets, sugarcane
• lignocellulosic biomass: wheat straw, switchgrass, short rotation woody crops
– Fischer-Tropsch diesel and Dimethyl ether (DME)
• lignocellulosic waste wood, short-rotation woody crops (poplar, willow), switchgrass
• LCAs are almost universally set in European or North American context
(crops, soil types, agronomic practices, etc.). One prominent exception is an
excellent Brazil sugarcane ethanol LCA.
• Extremely wide range reported for LCA results for GHG mitigation
– Across different biofuels
– Across different LCA studies for same biofuel
• Lack of focus on evaluating per-hectare GHG impacts.
– Most analyses report GHG savings per GJ biofuel.
– Some report GHG savings per-vkm.
– Few focus on understanding what approaches maximize land-use efficiency for GHG mitigation
• All studies are relatively narrow engineering analyses that assume one set of
activities replaces another.
From eric larson
outline
• Evolution of the components and boundaries of
life cycle
• Range of variation but have a general sense for
ethanol and biodiessel for main crops , largely
Eu and USA conditions
• When land use change is taking into account
– Show science paper with years needed to become
beneficial.
– Palm oil example
• When carbon sequestration is taking into
account