Greenhouse Gas Mitigation Benefits of
Expanding the U.S. Renewable Fuel Standard to
Promote Biomass Use in Chemical Feedstocks
I. Daniel Posen*,1,2
W. Michael Griffin1, H. Scott Matthews,1,2 and Inês Azevedo1
1Department
of Engineering and Public Policy
2Department of Civil and Environmental Engineering
Carnegie Mellon University
1
I. Background
2
Context: U.S. Biofuel Incentives
• Renewable Fuel Standard (RFS2)
– Established by Energy Independence and Security Act of 2007 (EISA)
– Sets minimum biofuel targets
– How are we doing?
138
60
Gasoline
Diesel
Production
in 2022:
Fuel Volume (Billion Gallons)
40
30
20
16 billion gal
Cellulosic Biofuel
Bio-diesel
Advanced Biofuel
5 billion gal
Renewable Biofuel
15 billion gal
10
0
2008
2012
2016
2020
3
Challenges
• Some Problems for the Renewable Fuel Standard
– Excess capacity faces demand-side limitations
– Ethanol is an imperfect substitute for gasoline
– Narrow scope
• Concurrent Problem:
– Chemical industry a major contributor to greenhouse gas emissions
and consumer of non-renewable energy (~5% in the U.S. )
• Possible Solution / Policy Recommendation:
– Expand RFS2 to include credits for chemical use of bio-ethanol
4
Chemical Use for Ethanol
• Ethylene case study
– Easily made from ethanol
– Critical building block for chemical industry
– Wide range of uses
• Biggest use: Polyethylene
5
Key Research Questions
• Can bio-based low density polyethylene (bio-LDPE) meet RFS2
greenhouse gas (GHG) targets?
• Does bio-LDPE achieve similar GHG benefits to bio-ethanol
fuel?
6
II. Methods
7
Overview
•
Life-Cycle Assessment (LCA) used to quantify greenhouse gas emissions from
various fuel and chemical pathways.
U.S.
Corn
U.S.
Switchgrass
Brazilian
Sugarcane
Ethanol
(1.74 kg)
Ethanol Fuel
Gasoline
(46.9 MJ)
Crude Oil
•
•
Bio-LDPE
Compare
(1 kg)
Compare
Compare
(46.9 MJ)
Fossil LDPE
(1 kg)
Natural Gas Ethane
Emphasis on quantifying uncertainty with Monte Carlo simulation.
Draws primarily on literature sources and Government Data
8
Model Overview: Fossil-LDPE (Natural Gas)
PRODUCTION
PROCESS
PRODUCTS
Pre-production
Lease Condensate
Dry Natural Gas
Extraction
Wet Natural
Gas
Dry Natural Gas
Propane
Butanes
Pentanes Plus
Processing
Ethane
Steam Cracking
Hydrogen
Propylene
Butadiene
Aromatics
Ethylene
Polymerization
LDPE (U.S.) (1 kg)
9
Model Overview: Bio-based Pathways
Switchgrass
Corn
Sugarcane
Switchgrass
Cultivation
Corn
Cultivation
Switchgrass
Cultivation
Feedstock
Transportation
Feedstock
Transportation
Feedstock
Transportation
Ethanol
Production
Ethanol
Production
Ethanol
Production
Ethanol (U.S.) (1.74 kg)
+ Electricity (U.S.)
Ethanol (U.S.) (1.74 kg)
Transport to
Ethylene plant
Fuel
Distribution
Dehydration to
Ethylene
Combustion
Polymerization
Ethanol (Brazil) (1.74 kg)
+ Electricity (Brazil)
Ethanol (U.S.) (1.74 kg)
+DDGS (U.S.)
Ethanol (Brazil) (1.74 kg)
Transport to
U.S.
Transport to
Ethylene plant
Dehydration to
Ethylene
Polymerization
Energy
(46.9 MJ)
LDPE (U.S.)
(1 kg)
Transport to
U.S.
10
III. Results
11
Simulated Emissions from Production of
Low Density Polyethylene (LDPE)
1.6
1.4
Probability Density
1.2
Corn LDPE
Fossil LDPE
1.0
Sugarcane LDPE
0.8
Switchgrass LDPE
0.6
0.4
0.2
0.0
-6
-4
-2
0
2
4
6
8
Life-cycle GHG Emissions (kg CO2e / kg LDPE)
12
Simulated Emissions from Production of
Ethanol and Gasoline
1.6
1.4
Probability Density
1.2
1.0
0.8
Switchgrass Ethanol
0.6
0.4
0.2
0.0
-6
-4
-2
0
2
4
6
8
Life-cycle GHG Emissions (kg CO2e / 46.9 MJ)
13
Net Emissions From Alternate Pathways
(kg CO2e/kg LDPE)(kg CO2e/46.9 MJ)
Bio-product has lower GHG
emissions than fossil counterpart
Bio-product has higher GHG
emissions than fossil counterpart
Bio-LDPE
Fuel Ethanol
(gasoline replacement)
Switchgrass
Sugarcane
Corn
• Both fuel
and feedstock
use of switchgrass
and sugarcane have
the potential to reduce (even capture) greenhouse gas emissions.
• Choice of feedstock is more important than how it is used
14
Can These Pathways Meet RFS2 Targets?
Advanced
biofuel target
Cellulosic
biofuel target
Probability that Emission
Reduction Exceeds Policy Target
Renewable
biofuel target
• Neither corn product can meet RFS2 targets
• Both sugarcane products can meet RFS2 targets
Bio-LDPE
Fuel Ethanol
(gasoline
replacement)
• Both Switchgrass products can meet RFS2 targets
Figure style inspired by
Mullins et al. (2011)
15
Summary
• Can the considered pathways meet RFS2 targets?
– Yes: U.S. Switchgrass and Brazilian Sugarcane (fuel or LDPE)
– No: for U.S. Corn Starch (fuel or LDPE)
• Does bio-LDPE achieve the same GHG benefits as
bio-ethanol fuel (any feedstock)?
– Yes: for Brazilian Production (>95% confidence)
– No: for U.S. Production (~80% confidence)
16
Conclusions
• RFS2 credits for bio-ethylene products provides flexibility to
obligated parties with no impact on end user
• Recommendation depends on goal of policy
–
–
–
–
Energy Security
Rural Development
Market Development
Greenhouse Gas Mitigation
• Recommendations (for greenhouse gas focus) :
– Incentives for corn ethanol production should be discontinued
– RFS2 credits should apply to imported Brazilian bio-LDPE
– RFS2 credits should be applied to U.S. Bio-LDPE only in a demandconstrained biofuel environment
17
Acknowledgements
•
•
•
•
•
•
•
•
•
Steinbrenner Institute
Colcom Foundation
Mike Griffin
Inês Azevedo
Scott Matthews
Kim Mullins
Aranya Venkatesh
Fan Tong
Stefan Schweitzke
This work is supported by a Steinbrenner Institute U.S. Environmental Sustainability Ph.D. Fellowship. The fellowship
program is supported by a grant from the Colcom Foundation, and by the Steinbrenner Institute for Environmental
Education and Research at Carnegie Mellon University.
18
I. Daniel Posen
Advisors: Mike Griffin, Scott Matthews, Inês Azevedo
Department of Engineering and Public Policy &
Department of Civil and Environmental Engineering
Carnegie Mellon University
Email Address: idp@andrew.cmu.edu
Image: Great Lakes Bioenergy Research Center
19
III. APPENDIX
20
Scope of Ethanol use for Ethylene
• Replacement of all current U.S. ethylene production:
– 14 billion gallons of ethanol
– Savings up to 110 MT CO2e for switchgrass mean reductions
(~1-2% of U.S. GHG emissions)
• Current US consumption of ethanol (2013): 14 billion gallons
• EISA 2022 Renewable fuel target: 36 billion gallons
• Ethylene replacement can double current ethanol production
and meet 60% of the remaining target
21
Projected Ethylene GHG Emissions
(in Function of Feedstock Choice)
350
GHG Emissions (Mt CO2e)
300
250
200
Bulk Chemicals
150
Full transition to switchgrass ethylene by 2040 would
Ethane mitigate:
Ethylene
100
Corn Ethylene
50
• >100% of emissions from ethylene productionSugarcane Ethylene
•
•
0
Switchgrass Ethylene
-50
Switchgrass Ethylene Net
~50%
of
direct
emissions
from
bulk
chemicals
production
-100
-150
A population
2010 2015
increase
of 102030
million
2020 2025
2035people
2040
(~17% of the projected population
Year increase over that time).
22
V. Rough Cost Analysis
23
Bio-ethylene is (currently) far less
competitive than bio-ethanol
Table 1. Implicit carbon price for bio-ethanol and bio-ethylene (90% confidence interval, $/ton CO2e)
Bio-ethanol
Bio-ethylene
Corn
N/A
N/A
Sugarcane
(-250) – 0
200-450
Switchgrass
0-100
300-700
24
Displacement of Gasoline vs Fossil LDPE
(Fossil LDPE – Bio LDPE) – (Gasoline – Bio ethanol)
Bio-ethanol achieves greater
GHG savings than bio-LDPE
Bio-LDPE achieves greater GHG
savings than bio-ethanol fuel
0.8
0.6
0.4
U.S.
Production
0.2
Brazilian
Production
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
0.0
-2.0
Probability that emissions difference
exceeds given level
1.0
Excess emission reduction from bio-LDPE bio-ethanol fuel
(kg CO2e/kg LDPE)(kg CO2e/46.9 MJ)
25
Displacement of Gasoline vs Fossil LDPE
Bio-ethanol achieves greater
GHG savings than bio-LDPE
Bio-LDPE achieves greater GHG
savings than bio-ethanol fuel
Probability that policy change meets target
1.0
0.8
0.6
0.4
U.S.
Production
0.2
Brazilian
Production
40%
30%
20%
10%
0%
-10%
-20%
-30%
-40%
• For U.S. Production: biomass fuel use has greater GHG benefits
than0.0chemical feedstock substitution (~80% confidence)
• For Brazilian
Production:
chemical
useto be
ofmet
biomass
has
Additional
GHG emissions
reduction target
by bio-LDPE
overgreater
bio-ethanol fuel (% of gasoline emissions)
GHG benefits than fuel
use (>95% confidence)
26
Model Overview
Fossil Fuel Pathways
Biomass Pathways
(Brazil)
Crude Oil
Natural Gas
Corn
Switchgrass
Sugarcane
Gasoline
(life-cycle)
Pre-production
Corn
Cultivation
Switchgrass
Cultivation
Switchgrass
Cultivation
Feedstock
Transportation
Feedstock
Transportation
Feedstock
Transportation
Ethanol
Production
Ethanol
Production
Ethanol
Production
Extraction
Wet Natural
Gas
Lease
Condensate;
Dry Natural Gas
DDGS
Processing
Ethane
(~1.25kg)
Steam
Cracking
Ethylene
(1.0lkg)
Dry Natural Gas;
Propane;
Butanes;
Pentanes Plus;
Electricity
Hydrogen
Propylene
Butadiene
Aromatics
Ethanol (1.74kg)
Ethanol (1.74kg)
Transport
to U.S.
Transport to
Ethylene plant
Dehydration to
Ethylene
Polymerization
Electricity
Fuel
Distribution
Combustion
Transport to
Ethylene plant
Dehydration to
Ethylene
Polymerization
Transport
to U.S.
Energy
(46.9 MJ)
LDPE (1kg)
Energy
(46.9 MJ)
LDPE (1kg)
27
IV. Importance and Sensitivity
28
Fossil Ethylene Emissions Dominated by
Steam Cracking
Pre-Production
Production
Processing
Steam Cracking
Polymerization
Mean
(kg CO2e/kg LDPE)
0.04
0.26
0.12
0.80
0.74
Standard
Deviation
0.01
0.08
0.17
0.27
0.08
Ethylene Subtotal
LDPE Total
1.23
2.0
0.35
0.37
Life-cycle Stage
0.26
0.32
1.40
0.34
0.11
Lower 90%
CI
0.03
0.17
0.02
0.36
0.64
Upper 90%
CI
0.06
0.37
0.33
1.26
0.87
0.28
0.19
0.72
1.4
1.77
2.6
Coefficient of Variation
29
Corn Emissions are evenly distributed
Corn LDPE
LUC
Corn farming
Ethanol production
Co-product credit
Transportation
Ethanol dehydration
Polymerization
EOL (growth credit)
Mean
(kg CO2e/kg LDPE)
1.3
2.0
2.0
-0.61
0.36
0.34
0.71
-3.1
Standard
Deviation
0.22
0.46
0.20
0.04
0.03
0.08
0.08
-
Coefficient of
Variation
0.17
0.23
0.10
-0.07
0.09
0.24
0.11
-
LDPE Total
2.9
0.56
0.20
Life-cycle Stage
Lower 90% Upper 90%
CI
CI
0.91
1.6
1.4
2.9
1.6
2.3
-0.68
-0.54
0.32
0.41
0.23
0.49
0.62
0.85
2.0
3.9
30
Electricity Credits are Critical for Switchgrass
Switchgrass LDPE
Life-cycle Stage
LUC
Switchgrass farming
Ethanol production &
electricity credit
Transportation
Ethanol dehydration
Polymerization
EOL (growth credit)
LDPE Total
Mean
(kg CO2e/kg LDPE)
0.6
0.56
Standard
Deviation
0.14
0.13
Coefficient of
Variation
0.25
0.23
Lower 90%
CI
0.34
0.39
Upper 90%
CI
0.8
0.82
-2.4
0.31
0.34
0.71
-3.1
1.20
0.01
0.08
0.08
-
-0.50
0.03
0.24
0.11
-
-4.4
0.30
0.23
0.62
-
-0.51
0.33
0.49
0.85
-
-3.1
1.2
-0.38
-5.1
-1.2
31
Sugarcane Emissions are Dominated by
Farming
Sugarcane LDPE
Life-cycle Stage
LUC
Sugarcane farming
Ethanol production &
electricity credit
Transportation
Ethanol dehydration
Polymerization
EOL (growth credit)
LDPE Total
Mean
(kg CO2e/kg LDPE)
0.2
0.82
Standard
Deviation
0.17
0.19
Coefficient of
Variation
1.01
0.23
Lower 90%
CI
-0.1
0.52
Upper 90%
CI
0.5
1.1
-0.041
0.3
0.2
0.2
-3.1
0.042
0.02
0.05
0.05
-
-1.0
0.06
0.30
0.32
-
-0.12
0.3
0.1
0.1
-
0.00
0.4
0.2
0.3
-
-1.4
0.26
-0.18
-1.8
-1.0
32
Surplus Electricity Sale is Essential for meeting Cellulosic
Targets
Probability that emission reduction
Exceeds policy target
Renewable
biofuel target
Advanced
biofuel target
Cellulosic biofuel
target
Switchgrass
Chemical use
(LDPE)
Sugarcane
Fuel use (gasoline
replacement)
With Surplus
Without
Surplus
Electricity Sale
Corn
Reduction target (% below LC gasoline)
33
Corn Sensitivity to Land-Use Change Emissions
Base Case: distribution from US EPA (2010)
2.5th Percentile
1.0
97.5th Percentile
Mode
0.9
Probability of meeting target
0.8
Break-even
0.7
Chemical use
(LDPE)
0.6
0.5
Fuel use (gasoline
replacement)
0.4
0.3
0.2
20% reduction
target
0.1
0.0
0
5
10
15
Tipper 2009d(26.6)
Dunn 2013d Tyner 2010
(26.6)
a: 2.5th percentile
b: median and above
c: “marginal” scenario
d: “mean” scenario
20
25
2010a
30
35
40
Plevin
Hertel 2010 (26.6)
Al Riffai 2010)
c
Tipper 2009
45
Searchinger 2008
Plevin 2010b
LUC Emissions (g CO2e / MJ corn ethanol)
50
Switchgrass Sensitivity to Land-Use Change Emissions
Base Case: distribution from US EPA (2010)
2.5th Percentile Mode 97.5th Percentile
1.0
0.9
Probability of meeting target
0.8
0.7
0.6
Chemical use
(LDPE)
0.5
0.4
Fuel use (gasoline
replacement)
0.3
0.2
Break-even
60% reduction target
0.1
0.0
0
10
Dunn 2013
(-1.5)
20
30
40
50
60
70
80
90
100
110
120
Taheripouri 2013
(1.3)
LUC Emissions (g CO2e / MJ Switchgrass ethanol)
130
140
150
Sugarcane Sensitivity to Land-Use Change Emissions
Base Case: distribution from US EPA (2010)
2.5th Percentile Mode
97.5th Percentile
1.0
0.9
Probability of meeting target
0.8
0.7
0.6
0.5
0.4
0.3
50% reduction target
Break-even
0.2
0.1
0.0
-10
0
10
20
Tipper
c
2010 Bauen 2010
Lywood
(min) (7.82-27.38)
2008
30
40
50
60
70
80
Tipper
2010
(max)
LUC Emissions (g CO2e / MJ Sugarcane ethanol)
90
100
V. Rough Cost Analysis
37
Bio-ethylene is (currently) far less
competitive than bio-ethanol
Table 1. Implicit carbon price for bio-ethanol and bio-ethylene (90% confidence interval, $/ton CO2e)
Bio-ethanol
Bio-ethylene
Corn
N/A
N/A
Sugarcane
(-250) – 0
200-450
Switchgrass
0-100
300-700
38
VII. The Bigger Picture
39
Next Questions
We already know bio-LDPE can offer a near-perfect GHG mitigation
strategy, but:
• What is the scope for emissions reduction from feedstock
substitution?
• How do chemical needs influence the picture of long-term resource
limits?
• What is the best use for biomass from a larger set of options?
• What is the best way to green the chemical industry?
40
Bulk Chemicals Projected Growth
Value of Shipments
400
300
Energy Consumption
200
100
0
2010 2015 2020 2025 2030 2035 2040
CO2 Emissions (Mt)
Greenhouse Gas Emissions
350
300
250
200
150
100
50
0
2010 2015 2020 2025 2030 2035 2040
Energy Consumption
(Quadrillion BTU)
Value of Shipments
(billion 2005 dollars)
500
8
7
6
5
4
3
2
1
0
2010 2015 2020 2025 2030 2035 2040
EIA (2014). Annual Energy Outlook
41
Projected Ethylene GHG Emissions
(in Function of Feedstock Choice)
350
GHG Emissions (Mt CO2e)
300
250
200
Bulk Chemicals
150
Full transition to switchgrass ethylene by 2040 would
Ethane mitigate:
Ethylene
100
Corn Ethylene
50
• >100% of emissions from ethylene productionSugarcane Ethylene
•
•
0
Switchgrass Ethylene
-50
Switchgrass Ethylene Net
~50%
of
direct
emissions
from
bulk
chemicals
production
-100
-150
A population
2010 2015
increase
of 102030
million
2020 2025
2035people
2040
(~17% of the projected population
Year increase over that time).
42
Projected Light Duty Vehicle (LDV) Fuel Use
140
Billion Gallons of Fuel
120
100
80
Motor Gasoline
60
Ethanol for LDV
40
20
0
2010
2015
2020
2025
Year
2030
2035
2040
EIA (2014). Annual Energy Outlook
43
Projected Light Duty Vehicle GHG Emissions
(in Function of Fuel Choice)
GHG Emissions (Mt CO2e)
2000
1500
Gasoline
1000
Corn Ethanol
Full transition from gasoline to switchgrass ethanol Sugarcane
by 2040Ethanol
would
500
mitigate:
0
Switchgrass Ethanol
• 70-120% of emissions from LDV gasoline use
•
-500
A population
increase
30-70
million
2010 2015
2020 of
2025
2030
2035people
2040
(~50-120% of the projected population
increase over that time).
Year
Switchgrass Ethanol
without electricity
44
Resource Limits: Land for bio-energy
“Bio-based chemicals and other biomaterials might add significantly to the growing biomass demand, yet
they are not usually included in biomass potential or demand estimates.” (Dornburg 2010).
• 2050 North American bio-energy potential: 38-102 EJ (Smeets 2006)
• 2030 U.S. potential with strict environmental controls: 5 EJ (UCS 2012)
Today
2040
Ethylene
1.2 EJ
1.8-2.0 EJ
All Chemical
Feedstocks
3.3 EJ
4.4-4.8 EJ
LDV
Gasoline/Ethanol
16 EJ
10-12 EJ
Total U.S. Energy
Needs
100 EJ
100-120 EJ
45
Long-term Conclusions
• Biofuels and bio-based chemicals offer substantial scope for
greenhouse gas mitigation
• Ethylene production need not present a long-term challenge for
greenhouse gas emissions
– Incentives to begin the long-term transition can be implemented
immediately
• Chemical production alone will not be resource limited
• Total U.S. food, energy and chemical needs may be resource limited
– Estimates of bio-energy production potential must be updated to reflect
chemical needs
46
Human Appropriation of Net Primary
Production (HANPP)
North America
NPP: 7 GtC / yr
HANPP: 1.6 GtC / yr (25%)
Additional HANPP from RFS :
• 0.15 GtC / yr
• 2% of NPP
• 10% of HANPP
Additional HANPP from replacing
all U.S ethylene:
• 0.06 GtC / yr
• 1% of NPP
• 4% of HANPP
World
NPP: 60 GtC / yr
HANPP: 15 GtC / yr (25%)
Additional HANPP from
replacing all world ethylene:
• 0.29 GtC / yr
• 0.5 % of NPP
• 2% of HANPP
47
Resource Limits: Land
• U.S Arable Land: 1.6 million km2
• World Arable land: 59 million km2
• Land used to replace all US ethylene:
– With Corn: 130 thousand km2 (8% of US arable land)
– With Switchgrass: 85 thousand km2 (5% of US arable land)
• Land use to replace global ethylene:
– With Corn: 670 thousand km2 (1% of arable land)
– With Switchgrass: 440 thousand km2 (0.7% of arable land)
48
Resource Limits: Land for bio-energy
• World bio-energy potential: 65-300 EJ (Van Vuuren 2009)
• U.S. primary energy consumption in 2012: 100 EJ
– Predicted growth through 2040: 0.3% per year (EIA 2013)
• Ethanol used to replace all U.S. ethylene: 1.1 EJ
• Ethanol used to replace global ethylene: 5.8 EJ
49
Long-term Conclusions
• Ethylene production need not present a long-term challenge
for greenhouse gas mitigation
– Incentives to begin the long-term transition can be implemented
immediately
• Ethylene production alone will not be resource limited
• Estimates of resource limits for bio-energy production must
be updated to reflect chemical needs
50
ORIGINAL APPENDIX
51
Model Overview
Fossil Fuel Pathways
Biomass Pathways
(Brazil)
Crude Oil
Natural Gas
Gasoline
(life-cycle)
Wet Natural
Gas
Corn
Switchgrass
Sugarcane
Ethanol (1.74kg)
Ethanol (1.74kg)
Ethane
(~1.25kg)
Ethylene
(1.0lkg)
Energy
(46.9 MJ)
LDPE (1kg)
Energy
(46.9 MJ)
LDPE (1kg)
Energy
(46.9 MJ)
LDPE (1kg)
52
Sources
• Fossil LDPE model inspired by modeling from Venkatesh et al.
(2011); data from multiple sources
• Corn and Switchgrass based on a reconstruction of Mullins et al.
(2011) with slight modification
• Sugarcane pathway based on a modified reconstruction of Seabra
et al. (2011) and Liptow and Tillman (2012)
• Ethanol dehydration from Kochar (1981)
• Polymerization as per Liptow and Tillman (2012)
• Distribution for Gasoline from Venkatesh et al. (2011)
53
Scope of Ethanol use for Ethylene
• Replacement of all current U.S. ethylene production:
– 14 billion gallons of ethanol
– Savings up to 110 MT CO2e for switchgrass mean reductions
(~1-2% of U.S. GHG emissions)
• Current US consumption of ethanol (2012): 13 billion gallons
• EISA 2022 Renewable fuel target: 36 billion gallons
• Ethylene replacement can double current ethanol production
and meet 60% of the remaining target
54
Cost of Bio-Ethylene Production
International Renewable Energy Agency (IRENA), Production of Bio-Ethylene: Technology Brief; 2013
55
Pre-Production
Weber and Clavin (2012):
• Well Pad Constructions
• Well Drilling
• Production of Chemicals for Hydraulic Fracturing
• Water Management for Hydraulic Fracturing
EPA and other sources:
• Well Completions and Workovers
– Conventional
– Unconventional (uncontrolled)
– Conventional (reduced emission)
56
Production
EIA State Level Data:
• Lease Fuel Consumption
• Natural Gas Vented and Flared
– Base Case assumes all flared
EPA GHG Inventory:
• Fugitive Methane
57
Processing
• Facilities matched from EPA Greenhouse Gas Reporting
Program and EIA Processing Capacity Database
– 222 facilities matched, accounting for 80% of processing
• Data treated for outliers and examined for both linear trends
and Heteroskedasticity
• Continuous distribution fitted to data weighted by average
daily processing
58
Processing Emission Data Fitting
0.45
0.40
0.30
0.25
0.20
0.15
0.10
0.05
15
Tons CO2e / MMCf Processed
12
9
6
3
0.00
0
Probability Density
0.35
59
Ethane Steam Cracking
•
Energy input required: 15-25 GJ/t ethylene (multiple sources)
– Simulated with uniform distribution
•
Distributions of products and losses simulated with triangular or uniform
distributions (multiple sources)
•
Ethylene, Propylene, Butadiene and Aromatics treated as products for
allocation
•
Hydrogen treated as product for system expansion
– Uniform distribution for emissions from steam reforming
•
All other products burned for fuel
•
Excess fuel requirements met by dry natural gas; Life-cycle emissions from
Venkatesh et al. (2011)
60
Natural Gas Pre-Production Parameters
Parameter
Well pad construction
Value or distribution
Triangular (0.05, 0.13, 0.3)
Units
g CO2e/MJ
Source
(Weber and Clavin 2012)
Well Drilling
Triangular (0.1, 0.2, 0.4)
g CO2e/MJ
(Weber and Clavin 2012)
Fracking Chemicals
Triangular (0.04, 0.23, 0.5)
g CO2e/MJ
(Weber and Clavin 2012)
Fracking Water Management
Triangular (0.04, 0.07, 0.1)
g CO2e/MJ
(Weber and Clavin 2012)
Gas venting for conventional well completions
Gas venting for conventional well workovers
Conventional well annual workovers
Operating Lifetime of Conventional well
Daily production for conventional well
Uncontrolled gas vented/flared for unconventional
completions and workovers
Unconventional Well Estimated Ultimate Recovery
Flowback Captured in Reduced Emission
Completions
0.71
0.05
1
5
0.15
tons CH4/completion
tons CH4/workover
workover/year
Years
MMscf/day
(U.S. EPA 2010)
(U.S. EPA 2010)
(Venkatesh, et al. 2011)
(Venkatesh, et al. 2011)
(Venkatesh, et al. 2011)
Normal (8900,2006067)
Mcf “CH4”/completion
(U.S. EPA 2012)
Triangular (0.5, 2, 5.3)
Bcf
(Weber and Clavin 2012)
90%
%
(U.S. EPA 2011)
Flare Efficiency
Uniform (51,100)
(100% for regulated scenario)
98%
Number of refractures per unconventional well
Bionomial (p = 0.01, n= 30)
#
Green Completion Percentage
51%
100% (for regulated scenario)
%
State by state
%
(U.S. EIA 2013c)
By NEMS region for each state
%
(U.S. EPA 2013a)
Percent of released gas which is flared
Convention unconventional percent of growth
withdrawals
2011 CO2 and CH4 content in raw natural gas
%
%
(Jiang, et al. 2011)
(Federal Register 2012)
(Jiang, et al. 2011)
(U.S. EPA 2012) for p
(U.S. EIA 2013h) for n
(U.S. EPA 2012)
(Federal Register 2012)
61
Natural Gas Production, Processing and Cracking
Parameter
Value or distribution
Units
Source
Production
Lease Fuel Consumed
Gas Vented and Flared
State by state (discrete
distribution)
State by state (discrete
distribution)
Triangular (.81*best, best,
1.30*best) by (aggregated)
NEMS region(s)
MMcf/year
MMcf/year
(U.S. EIA 2013c)
(data from 2011 reporting year)
(U.S. EIA 2013d)
(data from 2011 reporting year)
Mg CH4/year
(U.S. EPA 2013c)
(data from 2011 reporting year)
Log-logistic(1.66,2.12)
tons CO2e/MMcf
processed
Own Analysis of (U.S. EIA
2013b, U.S. EPA 2013a)
Specific Energy Required
Uniform (15,25)
GJ/t ethylene
(EC 2003, Ren et al. 2006,
Worrell et al. 2000)
Ethylene Produced
Propylene Produced
Butadiene Produced
Aromatics Produced
Hydrogen Produced
Methane Produced
C4 Components Produced
C5 and C6 Components Produced
Product Losses
Triangular (764, 803, 840)
Triangular (14.1, 16, 29.9)
Triangular (17.4, 19.9, 23)
Uniform (0, 19.9)
Triangular (57.9, 60, 89.7)
Triangular (58.8, 61, 70.1)
Triangular (0, 6, 8.1)
Uniform (0, 26)
Uniform (3, 20)
kg/ton ethane
kg/ton ethane
kg/ton ethane
kg/ton ethane
kg/ton ethane
kg/ton ethane
kg/ton ethane
kg/ton ethane
kg/ton ethane
(ACC 2004, EC 2003, Neelis et
al. 2005, Ren et al. 2006, Worrell
et al. 2000)
kg CO2e/kg H2
Multiple sources consulted.
Lower bound from (Boustead
2005) as cited in SimaPro
software. Upper bound from
(Spath and Mann 2001)
Production CH4 Emissions
Processing
Processing Emissions
Steam Cracking
Emissions from Hydrogen Production via steam
reforming (for system expansion)
Uniform (7.8, 12)
62
Corn Ethanol Parameters
Parameter
Land-use Change
Value or Distribution
Units
Domestic (Direct) Land
Use Change
Uniform (-4, 55)
kg CO2e/mmBtu
International (Indirect)
Land Use Change
Triangular (20.9, 31.8, 44.7)
kg CO2e/mmBtu
Lower bound from (U.S. EPA 2010b); upper
bound converted from (Fargione et al. 2008) as
cited in (Mullins et al. 2011)
Fit to confidence interval given by (U.S. EPA
2010b)
Beta (α=21.62, β=5.86, [0,14.3])
Mg dm/ha
(Mullins et al. 2011)
Nitrogen Application
Triangular (141, 150, 160)
kg N / ha
(Paz et al. 1999) as cited in (Mullins et al. 2011)
Crop residue applied
Triangular (73, 80, 86)
kg N / ha
Fossil Fuel Use
968
g CO2e / bushel
Corn starch content
Triangular(62.6, 67.3 ,72)
%w of dry matter
Heat input
Triangular (0.32, 0.42, 0.51)
MJ heat / MJ EtOH
Electricity input
Triangular (0.023,0.038,0.049)
MJ elec/MJ EtOH
Co-product credit
15
g CO2e/MJ EtOH
454
g CO2e/bushel
1000
km
0.0203
L diesel / t-km
Agricultural Operations
Corn Yield
Source
From (Klein et al. 2006) as modeled by (Mullins
et al. 2011)
Calculated from (Wang 2013)
Ethanol Production
Transportation
Feedstock transportation
Trucking distance for
ethanol to ethylene plant
Truck fuel consumption
(Kwiatkowski et al. 2006) and (Boyer and
Shannon 2003) as used in (Mullins et al. 2011)
(Kwiatkowski et al. 2006, McAloon et al. 2000,
Perrin et al. 2009) as cited in (Mullins et al.
2011)
(Plevin 2009) as cited in (Mullins et al. 2011)
Calculated from (Wang 2013)
Approximate distance from mid-west to gulf
states
(NREL 2013c)
63
Switchgrass Parameters
Parameter
Land-use Change
Domestic (Direct) Land Use Change
International (Indirect) Land Use
Change
Agricultural Operations
Switchgrass Yield
Nitrogen Application
Crop Residue Applied
Fossil Fuel Use
Ethanol Production
Glucan Content
Xylan Content
Mannan Content
Galactan Content
Arabinan Content
Lignin Content
Energy Input
Percent of energy to electricity, heat
Boiler efficiency
Turbine Efficiency
Transportation
Feedstock Transportation
Trucking distance for ethanol to
ethylene plant
Truck fuel consumption
Value or Distribution
Units
Uniform (-4, 55)
kg CO2e/mmBtu
Triangular (7.9, 15.1, 23.7)
Source
Lower bound from (U.S. EPA 2010b); upper
bound from (Fargione et al. 2008)
Fit to confidence interval given by (U.S.
kg CO2e/mmBtu
EPA 2010b)
Beta (α=21.62, β=5.86, [0,21.6])
Mg dm / ha
(Mullins et al. 2011)
Triangular (55, 74, 100)
kg N/ ha
Triangular (143.5, 133.5, 171.7)
kg N / ha
22
g CO2e/ kg SW
(McLaughlin and Walsh 1998, Schmer et al.
2008) as cited in (Mullins et al. 2011)
From (Klein et al. 2006) as modeled by
(Mullins et al. 2011)
Calculated from (Wang 2013)
Triangular (31, 34.4, 37.2)
Triangular (20.6, 23.0, 26.0)
Triangular (0.29, 0.32, 0.36)
Triangular (0.67, 1.0, 1.2)
Uniform (2.6, 3.4)
Triangular (17.3, 19.2, 21.1)
Uniform (0.44, 0.72)
%w
%w
%w
%w
%w
%w
MJ / MJ EtOH
10% / 90%
MJ
(Aden et al. 2002, Luo et al. 2009) as cited
in (Mullins et al. 2011)
15
g CO2e/ kg SW
1000
km
0.0203
L diesel / t-km
Calculated from (Wang 2013)
Approximate distance from mid-west to gulf
states
(NREL 2013c)
68%
85%
(U.S. DOE 2009) as cited in (Mullins et al.
2011)
64
Sugarcane Parameters
Parameter
Value or Distribution
Units
Source
Triangular (-3.7, 4.3,11)
g CO2e/MJ EtOH
(U.S. EPA 2010b)
Normal(86.7,13.4)
Normal (274,75)
t cane / ha
L diesel /ha
(Seabra et al. 2011)
(Seabra et al. 2011)
Nitrogen Application
Triangular (39, 777, 1515)
g N/t cane
(Seabra et al. 2011)
Trash burning
Emissions from Trash Burning
Triangular (3,82,126)
113
kg CO2e/t cane
g CO2e / kg straw
(Seabra et al. 2011)
(Wang 2013)
Normal (81.1, 4.3)
Exponential (10.7)
L EtOH/ t cane
kWh/t cane
(Seabra et al. 2011)
(Seabra et al. 2011)
Field to ethanol mill, fuel use
10300
kcal diesel/t cane
Ethanol to ethylene plant, fuel use
Shipping distance, Brazil (Parangua) to U.S.
(Houston)
Ship fuel consumption (Ocean Freighter)
0.217
MJ / kg ethanol
(Macedo et al. 2004) as cited in
(Liptow and Tillman 2009)
(Liptow and Tillman 2009)
10700
Km
(Sea-Rates 2013)
4.93 *10-3
L residual fuel oil/t-km
(NREL 2013b)
Land-use Change
Land-use change (total)
Agricultural Operations
Harvest Yield
Diesel Consumption
Ethanol Production
Ethanol yield
Surplus Electricity
Transportation
65
Common Parameters
Parameter
Value
Units
Ethanol Production (parameters
used for switchgrass and corn)
Hydrolysis yield
Fermentation yield from glucose
Uniform (0.85, 0.95)
Uniform (0.85, 1)
%
%
Fermentation yield from other sugars
Uniform (0.75, 0.9)
%
Ethanol Fuel Distribution
Emissions from fuel distribution
1.2
g CO2e/MJ
Calculated from (Wang 2013)
Ethanol dehydration to ethylene
Ethylene yield
Fuel used
Electricity Used
0.57
0.40
310
kg ethylene / kg ethanol
Gcal/t ethylene
kWh/t ethylene
Calculated from (Kochar et al. 1981)
(Kochar et al. 1981)
(Kochar et al. 1981)
451700
150
417
t/yr
kt/yr
GWh/yr
(Borealis 2008) as cited in
(Liptow and Tillman 2009)
On-site emissions
38.9
t CO2e/yr
Calculated from (Borealis 2008) as
cited in (Liptow and Tillman 2009)
LDPE share of energy consumption
0.40
Unitless
(Liptow and Tillman 2009)
Polymerization
Input Ethylene
Output LDPE
Electricity Used
Source
(Sheehan et al. 2003) as cited in
(Mullins et al. 2011)
66
Fuels, Electricity and Agrochemicals
Parameter
Fuel Emissions
Gasoline life-cycle emissions
Diesel life-cycle emissions
Residual fuel
Value
Units
Source
Log-logistic (2.2, 0.2, 80)
Log-logistic (2.3, 0.2, 82)
Log-logistic (2.3, 0.3, 83)
g CO2e/MJ (LHV)
g CO2e/ MJ (LHV)
g CO2e/ MJ (LHV)
Normal (66, 3.5)
Normal (73, 3.9)
g CO2e/MJ (HHV)
g CO2e/MJ (LHV)
(Venkatesh et al. 2011a)
(Venkatesh et al. 2011a)
(Venkatesh et al. 2011a)
Approximate distribution
selected; fit to parameters from
(Venkatesh et al. 2011b);
Brazilian electricity (average)
35
g CO2e/MJ
U.S. electricity
TRE Electricity
MRO Electricity
168
164
200
g CO2e/MJ
g CO2e/MJ
g CO2e/MJ
Calculated from (Coltro et al.
2003) as cited in (Liptow and
Tillman 2012) SI.
(Wang 2013)
(Wang 2013)
(Wang 2013)
4.8
5.4
kg CO2e/kg N
kg CO2e/kg N
Calculated from (Wang 2013)
Calculated from (Wang 2013)
Triangular (0.003, 0.01, 0.03)
kg N2O-N/kg N applied
Natural gas life-cycle emissions
Electricity Emissions
Agrochemicals
U.S. Fertilizer production
Brazilian Fertilizer Production
Direct N2O from synthetic fertilizer
and crop residue
Volatilization from synthetic
fertilizer
Indirect N2O from volatized N
Triangular (0.03, 0.1, 0.3)
Triangular (0.002, 0.01, 0.05)
Runoff/Leaching of N from
Triangular (0.1, 0.3, 0.8)
synthetic fertilizer and crop residue
Indirect N2O from runoff
Triangular (0.0005, 0.0075, 0.025)
(kg NH3-N + kg NOx-N)
/kg N
kg N2O-N
/ (kg NH3-N + kg NOx-N)
(Klein et al. 2006)
kg N runoff / kg N applied
kg N2O-N/kg N runoff
67
Energy and Mass Densities
Liquids
Item
Gasoline
Diesel/distillate, etc.
Residual Fuel Oil
Ethanol
Ethane (liquefied)
Propane (liquefied)
n-Butane (liquefied)
Isobutane (liquefied)
Pentanes plus
n-Hexane
LHV Energy Density
(btu/gal)
112,194a
128,450a
140,353a
76,330a
84,250a
94,970a
90,060a
105,125a
HHV Energy Density
(btu/gal)
120,439a
137,380a
150,110a
84,530a
91,330b
103,000b
94,620b
110,000b
-
LHV Energy Density
(btu/ft3)
983a
962a
290a
HHV Energy Density
(btu/ft3)
1,089a
1,068a
343a
Mass Density
2,836a g/gal
3,167a g/gal
3,752a g/gal
2,988a g/gal
546.5d kg/m3
582d kg/m3
601.4d kg/m3
593.4d kg/m3
651c kg/m3
655a kg/m3
Gasses
Item
Natural gas
Methane
Hydrogen
Solids
22a g/ft3
20.3a g/ft3
2.55a g/ft3
Solids
Item
Glucan/Cellulose
Xylan
Mannan
Galactan
Arabinan
Lignin
Mass Density
HHV Energy Density
(MJ/kg)
16.9e
17.4e
16.6e
17.2e
16.9e
25.1e
Item
Glucose
Xylose
Mannose
Galactose
Arabinose
Non-sugar, non-lignin
switchgrass components
HHV Energy Density
(MJ/kg)
15.6f
15.6f
15.6f
15.5f
15.6f
11.8e
68
Summary Statistics for Natural Gas LDPE
Pre-Production
Production
Processing
Steam Cracking
Polymerization
Mean
(kg CO2e/kg LDPE)
0.04
0.22
0.13
0.66
0.79
Standard
Deviation
0.01
0.07
0.19
0.24
-
Ethylene Subtotal
LDPE Total
1.1
1.9
0.31
0.32
Life-cycle Stage
0.23
0.30
1.47
0.37
-
Lower 90%
CI
0.03
0.16
0.02
0.26
-
Upper 90%
CI
0.05
0.31
0.36
1.05
-
0.30
0.17
0.61
1.4
1.5
2.3
Coefficient of Variation
69
Summary Statistics for Corn Pathways
Corn Ethanol
LUC
Corn farming
Ethanol production
Co-product credit
Transportation
Mean
(g CO2e/MJ)
31
43
37
-15
4.0
Standard
Deviation
4.6
8.7
3.4
0.18
Coefficient of
Variation
0.15
0.2
0.09
0.04
Lower 90%
CI
23
31
31
3.7
Upper 90%
CI
39
59
42
4.3
Ethanol fuel Total
100
10
0.10
86
120
Life-cycle Stage
Corn LDPE
LUC
Corn farming
Ethanol production
Co-product credit
Transportation
Ethanol dehydration
Polymerization
EOL (growth credit)
Mean
(kg CO2e/kg LDPE)
1.4
2.0
1.7
-0.61
0.31
0.30
0.79
-3.1
Standard
Deviation
0.41
0.41
0.16
0.01
-
Coefficient of
Variation
0.31
0.20
0.09
0.03
-
LDPE Total
2.8
0.49
0.18
Life-cycle Stage
Lower 90% Upper 90%
CI
CI
1.1
1.8
1.5
2.8
1.5
2.0
0.30
0.33
-
2.0
3.7
70
Summary Statistics for Switchgrass Pathways
Switchgrass Ethanol
Life-cycle Stage
LUC
Switchgrass farming
Ethanol production &
electricity credit
Transportation
Ethanol fuel Total
Mean
(g CO2e/MJ)
23
12
Standard
Deviation
6.6
2.5
Coefficient of
Variation
0.29
0.21
Lower 90% Upper 90%
CI
CI
12
33
8.4
17
-34
3.2
17
0.11
-0.49
0.03
-62
3.1
-7.4
3.4
3.4
17
5.2
-26
31
Switchgrass LDPE
Life-cycle Stage
LUC
Switchgrass farming
Ethanol production &
electricity credit
Transportation
Ethanol dehydration
Polymerization
EOL (growth credit)
LDPE Total
Mean
(kg CO2e/kg LDPE)
1.1
0.56
Standard
Deviation
0.31
0.12
Coefficient of
Variation
0.29
0.21
Lower 90%
CI
0.56
0.39
Upper 90%
CI
1.6
0.77
-1.6
0.28
0.30
0.79
-3.1
0.78
0.01
-
-0.49
0.03
-
-2.9
0.27
-
-0.35
0.29
-
-1.8
0.81
-0.45
-3.2
-0.5
71
Summary Statistics for Sugarcane Pathways
Sugarcane Ethanol
Life-cycle Stage
LUC
Sugarcane farming
Ethanol production &
electricity credit
Transportation
Ethanol fuel Total
Mean
(g CO2e/MJ)
4
17
Standard
Deviation
3.7
4.1
1.01
0.23
Lower 90%
CI
-2.6
11
Upper 90%
CI
10
24
-0.88
11
0.89
0.64
-1.0
0.06
-2.7
10
-0.04
12
31
5.5
0.18
22
41
Coefficient of Variation
Sugarcane LDPE
Life-cycle Stage
LUC
Sugarcane farming
Ethanol production &
electricity credit
Transportation
Ethanol dehydration
Polymerization
EOL (growth credit)
LDPE Total
Mean
(kg CO2e/kg LDPE)
0.2
0.82
Standard
Deviation
0.17
0.19
Coefficient of
Variation
1.01
0.23
Lower 90%
CI
-0.1
0.52
Upper 90%
CI
0.5
1.1
-0.041
0.3
0.2
0.3
-3.1
0.042
0.02
-
-1.0
0.06
-
-0.12
0.3
-
0.00
0.4
-
-1.4
0.26
-0.18
-1.8
-1.0
72
Bio-LDPE GHG Equivalence Factor 1
Switchgrass
Sugarcane
73
Probability that bio-LDPE achieves same
emission reduction as bio-ethanol fuel
Bio-LDPE Equivalence Factor 2
Sugarcane
Switchgrass
Bio-LDPE Equivalence factor
74
Corn Ethanol Importance Analysis
75
Corn LDPE Importance Analysis
76
Switchgrass Ethanol Importance Analysis
77
Switchgrass LDPE Importance Analysis
78
Sugarcane Ethanol Importance Analysis
79
Sugarcane LDPE Importance Analysis
80
Net Emissions – Sensitivity to Surplus Electricity
(kg CO2e/kg LDPE)(kg CO2e/46.9 MJ)
Bio-product has lower GHG
emissions than fossil counterpart
Bio-product has higher GHG
emissions than fossil counterpart
Chemical use
(LDPE)
Fuel use
(gasoline replacement)
Switchgrass
Sugarcane
Corn
With Surplus
Without
Surplus
Electricity Sale
81
Sensitivity to Land Use Change
Base Case
(kg CO2e /
functional Unit)
No LUC
(kg CO2e /
functional Unit)
Switchover LUC
emissions
(g CO2e/MJ ethanol)
Corn Ethanol
+1.3
-1.3
28
Corn LDPE
+1.6
-1.0
20
Sugarcane Ethanol
-2.7
-2.9
62
Sugarcane LDPE
-3.3
-3.4
73
Switchgrass Ethanol
-4.1
-5.1
109
Switchgrass LDPE
-3.7
-4.7
101
82
Comparison to Other Studies
• Corn results
– Similar to Mullins et al. (2011)
– Higher emissions than EPA (2010) due to DLUC and fertilizer use
• Switchgrass results
– Lower Emissions than Mullins et al. (2011) due primarily to surplus
electricity accounting
• Sugarcane results
– Higher than Seabra et al. (2011) due to displaced electricity
accounting and LUC
– Lower than Liptow and Tillman (2012) due to EOL
83
After this are less relevant slides
84
Growing Interest in Bio-based Chemicals
•
•
•
•
•
•
Long term sustainability
Reduced Environmental Impact
Resource Security
Unexploited economic and technological potential
Corporate image and sales
Rural Economic Development
85
Ethylene Production Continues to Grow
True (2010). OGJ FOCUS:Global ethylene production.
86
Major plastics and their uses
• Annual Production
Volumes (Shen et al.
2009)
–
–
–
–
–
–
–
HDPE: 31 million tons
LDPE: 37 million tons
PP: 45 million tons
PS: 16 million tons
PA: 3 million tons
PET: 15 million tons
PVC: 35 million tons
Goodship, V. (2007). Introduction to Plastics Recycling.
87
Bio-Based Chemicals: Possible Challenges
• Technical Potential and Unproven Technologies
• Environmental Impact
• Availability Resources and Competition with Other Needs
• Crop Variability
• Cost
88
Alternate Strategies
• Mode of Substitution
– Direct (e.g. Ethylene)
– Functional (e.g. PLA)
Dornburg et al. (2008) Environmental Science & Technology 42(7): 2261-2267.
• Scope of Production
– Single Product
– Full system (e.g.
Biorefinery)
Bottom: U.S. DOE (2004). Top Value Added Chemicals from Biomass, Volume
89 I
2. Total Potential of Renewable Feedstocks
• Focus on technical
potential – long-term
vision
• Existing studies have
focussed on market
potential (see figure)
• Others focus on
potential for energy
production
Market Potential for biobased bulk Chemicals in Europe (high scenario)
Dornburg et al. (2008) Environmental Science & Technology 42(7): 2261-2267.
90
1. Existing Studies on Bio-ethylene
•
Bos et al. (2010),
–
–
–
–
–
•
LCA of polyethylene from 6 different sources
No land use change
Deterministic Analysis
European Context
See figure for GHG results; NREU qualitatively
similar.
Liptow and Tillman (2012)
– Comparative LCA of Polyethylene from
Brazilian Sugar Cane and Saudi Crude oil
– Largely deterministic analysis
– European context
– Critical role of Land use change
– Generally, sugar cane (mildly) preferable for
GHG and NREU, while oil route preferred for
ACP, EU, CED.
Bos et al. (2010). Sustainability aspects of biobased applications, Report 1166.
Liptow and Tillman (2012). Journal of Industrial Ecology 16(3): 420-435.
91
Technical Substitution Potential
Shen et al. (2010) Biofuels Bioproducts & Biorefining-Biofpr 4(1): 25-40
92
Additional Motivations
• Asymmetric Incentives
– EISA, RFS
– USDA Biopreferred
• Competing Uses For Biomass
• Competing mechanisms to improve
impacts of chemical industry
• Existing corporate ventures
– Coca Cola, Heinz, P&G…
http://coke-stuff.blogspot.com/2013/04/the-bottle.html
• Long term sustainability and
Carrying Capacity
93