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Environmental Impacts of Biofuels:
Lifecycle greenhouse gas emissions
Mississippi State University
January 28 2014
Valerie Thomas
School of Industrial and Systems Engineering, and
School of Public Policy
Biofuel motivation 1
Reduce risk of oil embargos, price spikes,
geopolitical dependence
Middle East Conflict
Six day war - June 5 1967
Arab oil embargo - June 6
Yom Kippur War - 1973
Arab Oil Embargo - 1973
Iranian Revolution - 1979
Crude oil prices since 1861
BP Statistical Review of World Energy 2010
Biofuel motivation 2
Support US farmers
Similar motivation for ethanol production from
sugar cane in Brazil
Biofuel motivation 3
Reduce greenhouse gas emissions
Coal: C135H96O9NS … (or CH for short)
Petroleum (octane): C8H18 …
Natural Gas (methane): CH4
C +O2 ® CO2
1 kg C corresponds to 44/12 kg CO2
1 kg uncombusted CH4 corresponds to 25 kg CO2e in 100 year time horizon.
Earth’s Spectrum Shows GHG effects
Archer, Chp. 4, Greenhouse Gases
Water is a Greenhouse Gas
Water Excitation Levels
Archer, Chp. 4, Greenhouse Gases
CO2 excitation levels
Archer, Chp. 4, Greenhouse Gases
Effectiveness of Greenhouse Gases
Depends on Their Radiative Efficiency
and Time Dependent Decay
Radiative Efficiency: W/m2/kg
Time dependent decay: x(t)
Selected Greenhouse Gases
The CO2 response function used in this report is based on the revised
version of the Bern Carbon cycle model used in Chapter 10 of this report
(Bern2.5CC; Joos et al. 2001) using a background CO2 concentration
value of 378 ppm. The decay of a pulse of CO2 with time t is given by
3
a0 + å ai e-t/t i
i=1
where a0 = 0.217, a1 = 0.259, a2 = 0.338, a3 = 0.186, τ1 = 172.9 years, τ2 = 18.51 years,
IPCC 2007
and τ = 1.186 years.
Global Warming Potential
TH is time horizon, a is radiative efficiency of increase of one unit of
substance (W/m2/kg); x and r are time dependent decay of substance x
and reference gas r.
Selected Greenhouse Gases
IPCC 2007
Atmospheric CO2 for 400,000 years
Carbon dioxide concentrations in Antarctica over 400,000 years. “The
graph combines ice core data with recent samples of Antarctic air. The
100,000-year ice age cycle is clearly recognizable.” (Data sources: Petit et
al. 1999; Keeling and Whorf 2004; GLOBALVIEW-CO2 2007.)
Anthropogenic Carbon Emissions
Boden et al. 2011
Mauna Loa Data Set
Biofuel motivation 3
Reduce greenhouse gas emissions
Biomass is often credited with zero greenhouse gas emissions
www.wfpa.org
Life Cycle Assessment
Assessment of the
environmental impacts of a
product or service including
• raw material extraction,
• manufacturing,
• distribution,
• use, and
• end of life.
US Renewable Fuel Standard
US EISA
US Renewable Fuel Stadnard (RFS2)
Lifecycle Greenhouse Gas Emissions
Requirements Compared to Petroleum Fuels
• advanced renewable fuels < 50 %
• cellulosic renewable fuels < 40 %
• funding for development < 20 %
Lifecycle Energy and GHG Emissions from
Ethanol Produced by Algae
Ron Chance, Matthew Realff, Valerie Thomas
Zushou Hu, Dexin Luo, Dong Gu Choi
School of Chemical and Biomolecular Engineering, and
School of Industrial and Systems Engineering
System Boundary for LCA
LCA Results Depend on Initial Ethanol Concentration
Analysis Framework: Consider Baseline
and Two Extensions
Baseline
Extension 1
Extension 2
Initial
Concentration
 1 wt%
Initial Concentration
 0.5~5.0 wt%
Initial Concentration
 0.5~5.0 wt%
External Energy
Supply
 CHP + Natural gas
 Grid Electricity+
Natural gas
 CHP + Solar thermal
+ Natural gas
External Energy Supply
 CHP + Natural gas
 Grid Electricity+
Natural gas
 CHP + Solar thermal +
Natural gas
External Energy
Supply
 CHP+ Natural gas
Heat Exchange
Efficiency
 80%
Heat Exchange
Efficiency
 80%
Heat Exchange
Efficiency
 90%
1
Production Rate
Fertilizer Energy and
GHG emissions
Ethanol:
56,000 l/hectare
Waste Biomass: 0.97 ton/hectare
Algae Composition (1)
Nitrogen:
Phosphorous:
8 wt%
0.3 wt%
Energy and GHG emissions
Nitrogen:
Phosphorous:
Fertilizer Parameters (2-3)
Nitrous Dioxide:
0.0017 MJ/MJEtOH
0.11 g CO2e/MJEtOH
0.000017 MJ/ MJEtOH
0.0026 g CO2e/MJEtOH
0.1 g CO2e/MJEtOH
Nitrogen:
23.7 MJ/kg
Nitrogen:
1.675 kg CO2e/kg
Phosphorous:
5.78 MJ/kg
Phosphorous:
0.97 kg CO2e/kg
Nitrous Dioxide: 0.005 g N2O /g N
(1) ECN, Phyllis: The Composition of Biomass and Waste. 2010. http://www.ecn.nl/phyllis/
(2) Kongshaug, G., Energy consumption and greenhouse gas emissions in fertilizer production. IFA Technical Conference, Marrakech, Morocco, 1998.
(3) US DOE, Agricultural Chemicals: Fertilizers, Energy and Environmental Profile of the U.S. Chemical Industry. Energy and Environmental Profile of the U.S. Chemical
Industry, Chapter 5. Technologies, O. o. I. 2000
Bioreactor Production and Disposal
2
Assumptions
1
Photo-bioreactor systems to be replaced every 5 years;
2 No GHG emissions from drained bioreactors;
Production of Polyethylene (1)
Energy use:
GHG emissions:
Dimension of the PBR
76 MJ/kg
1.9 kg CO2e /kg
Length:
Circumference:
Wall thickness:
Results
Energy use:
0.05 MJ/MJEtOH
GHG emissions: 1.3 g CO2e/MJEtOH
(1) GREET, ANL
50 feet
12.6 feet
5~10 mil
Ethanol Distribution and Combustion
Assumptions from GREET Model
3
1
40% barge:
520 miles
0.54 MJ/ton-mile
2 40% railroad tanks:
800 miles
0.36 MJ/ton-mile
3 20% trucks:
80 miles
0.9 MJ/ton-mile
4 0.0031 g CH4 and 0.0024 g N2O per MJ of ethanol combusted
Results
Distribution:
Combustion:
0.017 MJ/MJEtOH
1.6 g CO2e/MJEtOH
0.84 g CO2e/MJEtOH
Freight Truck Energy Intensity
8000
7000
Btu/ton-mile
6000
5000
Single Unit Truck
4000
Combination Truck
3000
2000
1 mile = 1.6 km
1 ton = 0.907 tonnes
1 Btu = 1055 J
1000
0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Air freight energy intensity
80,000
70,000
Btu/ton-mile
60,000
50,000
40,000
30,000
20,000
10,000
0
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Freight energy intensity
4,500
4,000
Btu/ton-mile
3,500
3,000
Truck
2,500
Rail
2,000
Water
Pipeline
1,500
1,000
500
0
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
CO2 Delivery and Water Consumption
Assumptions
4
1
Source water pumped from a depth of 100 meters;
2 Water is circulated to the power plant 6 km away;
3 Reverse osmosis seawater desalination; (1)
4 No water loss through evaporation.
Results
Water pumping:
Carbonation:
Water consumption
Reverse osmosis:
0.002 kWh/MJEtOH
0.00090 kWh/MJEtOH
0.926 l/lEtOH
9.5×10-5 kWh/MJEtOH
(1) National Research Council Review of the Desalination and Water Purification Technology Roadmap; Washington, DC, 2004
5 6 7
Ethanol Separation Process
Ethanol Separation Process Compression Energy
5
Processes: Vapor Compression Steam Stripping and Distillation
Inputs
1
HYSYS
simulation
0.051 MJ/MJEtOH
P
2 T
Efficiencies
W adiabatic
 P

   out
  1   Pin

nRT




 1

 1

0.055 MJ/MJEtOH
Ethanol Separation Process Evaporation Energy & Molecular
Sieve
6
7
Evaporation Processes: Vapor Compression Steam Stripping
Inputs
1
wt%
Efficiencies
HYSYS
simulation
0.16 MJ/MJEtOH
1 heat exchange
2 column eff.
2 T
E evap 
m
i
0.17 MJ/MJEtOH
H (T ) i
v
i
Final Purification Processes: Molecular Sieve

- The total heat requirement : 1 ~ 2 MJ/kgEtOH.
(1)
- In this study : 1.5 MJ/kgEtOH, or 0.056 MJ/MJEtOH
(1) Cho, J.; Park, J.; Jeon, J.-k., Comparison of three- and two-column configurations in ethanol dehydration using azeotropic distillation. J. Ind. Eng. Chem.
(Seoul, Repub. Korea) 2006, 12 (2), 206-215.
Baseline Energy Use per MJ of Ethanol Produced
for Process Steps at 1wt%
1
2
3
4
5
6
7
Baseline GHG Emissions for 1wt%
at 80% heat exchange efficiency
1
2
3
4
5
6
7
Baseline GHG Emissions for 1wt% at 80% and
90% heat exchange efficiency
1
2
3
4
5
6
7
External Energy Supply Scenarios
S1
Electrical energy
U.S. grid electricity
Process heat
Natural gas
S2
Electrical energy and heat
Natural gas fueled CHP
Extra Process heat
Natural gas
Electrical energy and heat
Natural gas fueled CHP
S3
Process heat
14 hr Natural gas
10 hr Solar thermal
700 g CO2e/kWhe
50.38 g CO2e/MJEtOH
478 g CO2e/kWhe
50.38 g CO2e/MJEtOH
478 g CO2e/kWhe
50.38 g CO2e/MJEtOH
0 g CO2e/MJEtOH
Lifecycle GHG Emissions
for 80% and 90% heat exchange efficiencies 0.5wt%~5wt%
g CO2e/MJ Ethanol
DOE target of 40% of the gasoline emission
DOE target of 20% of the gasoline emission
Ethanol wt % from phtobioreactors
Life Cycle Inventory Assessment
How does the ethanol concentration and mix of fuels to generate heat and power influence
the ability of the system to meet RFS?
Natural Gas + US Grid
Natural Gas CHP
Natural Gas CHP + Solar Thermal
Conclusion and Discussion
 DOE 40% goal (36.5 g CO2e/MJEtOH) achievable by all three energy supply scenarios
and initial concentration as low as 0.5%
 DOE 20% goal (18.3 g CO2e/MJEtOH) more challenging
 Advantage 1: the potential to locate production facilities on low-value, arid, nonagricultural land, and the resulting avoidance of competition with agriculture
 Advantage 2: no-harvest strategy has the potential for more energy efficient
separations, lower fertilizer requirements, and lower water usage in comparison to
other algae biofuel processes.
 Technical challenge: the algae- produced ethanol system does not produce extra
biomass waste that can be used as energy to power the process
Does making ethanol use more fossil
energy and release more greenhouse gases
than the gasoline it is designed to replace?
Farrell et al. 2006. Ethanol Can Contribute to Energy and Environmental Goals. Science 311:506.
Sources of biomass carbon emissions
• Production, transport use fossil fuel
• Soil carbon loss
(direct or indirect)
• Regeneration time
Sample Bioenergy Lifecycle CO2e Emissions
Thomas and Liu 2013
Assessment of Alternative Fibers
Valerie Thomas, Wenman Liu, Norman Marsolan
Institute for Paper Science and Technology
School of Industrial and Systems Engineering
School of Public Policy
Georgia Institute of Technology
Arundo donax
Perennial
Grown for bioenergy
High yield
Low input
Invasiveness
Kenaf
Annual
Grown for fiber
Medium yield
Low input
Bamboo
Perennial
Widely grown in China
High yield
Low input
Invasiveness
Wheat Straw
Agricultural residue
No additional:
- land use
- fertilizers
- pesticides
- irrigation
Northern softwood
Biodiversity
Carbon storage
Low input
Bamboo as alternative
Recycled Fiber
Moderate
- energy use
- carbon footprint
- environmental impact
Kenaf, arundo, wheat straw as alternatives
What drives the results
•
•
•
•
•
•
•
•
Yield
Irrigation
Fertilizers
Pesticides
Agricultural Energy Use
Invasiveness
Biodiversity
Pulping process change
Preliminary Comparison: Yield
Preliminary Comparison: Water
Deinked Pulp
irrigation
Northern softwood
process water
Bamboo
Arundo donax
Kenaf
Wheat straw
0
100
200
300
400
m3/ton
500
600
700
Preliminary Comparison:
Nitrogen Fertilizer
Other
Deinked Pulp
Kengro
Northern softwood
GTP
Bamboo
KC China
Arundo donax
Kenaf
Wheat straw (10%)
0
20
40
60 80
kg N/ton
100 120
Eutrophication, energy input, greenhouse gas emissions
Standard Methods Provide
•
•
•
•
•
•
Land use
Fossil fuel energy use
Freshwater use – Irrigation and Processing
Greenhouse gases from energy and chemicals
Eutrophication
Ecotoxicity
Preliminary Results – Illustrative Only
Multiple Impact Categories
Net greenhouse gas emissions from each fiber
option under a 100-year time horizon
3000
2500
Landfill emissions
Biogenic to mill
2000
1500
Transport
Agriculture
1000
Sum total
500
0
Northern softwood
Bamboo
Recycled fiber
Wheat straw (10%)
Kenaf (35%)
-500
Arundo donax
kg CO2e/t pulp
Pulping
Net greenhouse gas emissions from each fiber
option under a 500-year time horizon
1000
600
Landfill emissions
400
Biogenic to mill
200
Pulping
0
Transport
-200
Agriculture
-400
Sum total
-600
-800
Northern softwood
Bamboo
Recycled fiber
Wheat straw (10%)
Kenaf (35%)
-1000
Arundo donax
kg CO2e/t pulp
800
Biodiversity
Driver for northern forest protection
– Effect from reducing northern softwood
harvesting
– Effect from growing bamboo on southern
timberland
– Effects of kenaf and arundo
Species richness,
Ecosystem scarcity,
Ecosystem vulnerability
Carbon storage
Driver for northern forest protection
• Effect from reducing northern softwood
harvesting
• Effect from growing bamboo on southern
timberland
• Effects of kenaf and arundo
Carbon storage in soils is known to be very
highly variable.
Biogenic Global Warming Potentials
Data from Guest et al. J. Indust. Ecol. 2012.
LCA of paper from alternative fibers
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