environmental impacts of biofuels: lifecycle greenhouse gas emissions mississippi state university...
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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. - PowerPoint PPT PresentationTRANSCRIPT
Environmental Impacts of Biofuels: Lifecycle greenhouse gas emissions
Mississippi State UniversityJanuary 28 2014
Valerie ThomasSchool of Industrial and Systems Engineering, and School of Public Policy
Biofuel motivation 1Reduce risk of oil embargos, price spikes,
geopolitical dependence
Middle East Conflict
Six day war - June 5 1967Arab oil embargo - June 6
Yom Kippur War - 1973Arab Oil Embargo - 1973Iranian Revolution - 1979
Crude oil prices since 1861
BP Statistical Review of World Energy 2010
Biofuel motivation 2Support US farmers
Similar motivation for ethanol production from sugar cane in Brazil
Biofuel motivation 3Reduce greenhouse gas emissions
Coal: C135H96O9NS … (or CH for short)
Petroleum (octane): C8H18 …
Natural Gas (methane): CH4
1 kg C corresponds to 44/12 kg CO2
1 kg uncombusted CH4 corresponds to 25 kg CO2e in 100 year time horizon.
Archer, Chp. 4, Greenhouse Gases
Earth’s Spectrum Shows GHG effects
Archer, Chp. 4, Greenhouse Gases
Water is a Greenhouse GasWater Excitation Levels
Archer, Chp. 4, Greenhouse Gases
CO2 excitation levels
Effectiveness of Greenhouse Gases Depends on Their Radiative Efficiency
and Time Dependent Decay
Radiative Efficiency: W/m2/kgTime dependent decay: x(t)
Selected Greenhouse Gases
IPCC 2007
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
where a0 = 0.217, a1 = 0.259, a2 = 0.338, a3 = 0.186, τ1 = 172.9 years, τ2 = 18.51 years, and τ3 = 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
www.wfpa.org
Biofuel motivation 3Reduce greenhouse gas emissions
Biomass is often credited with zero greenhouse gas emissions
Life Cycle AssessmentAssessment of the environmental impacts of a product or service including • raw material extraction, • manufacturing, • distribution, • use, and • end of life.
US Renewable Fuel StandardUS 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 ThomasZushou 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
Initial Concentration 1 wt%
External Energy Supply CHP+ Natural gas
Heat Exchange Efficiency 80%
Extension 1
Initial Concentration 0.5~5.0 wt%
External Energy Supply CHP + Natural gas Grid Electricity+ Natural gas CHP + Solar thermal + Natural gas
Heat Exchange Efficiency 80%
Initial Concentration 0.5~5.0 wt%
External Energy Supply CHP + Natural gas Grid Electricity+ Natural gas CHP + Solar thermal + Natural gas
Heat Exchange Efficiency 90%
Extension 2
Fertilizer Energy and GHG emissions
Production Rate
Ethanol: 56,000 l/hectareWaste Biomass: 0.97 ton/hectare
Algae Composition (1)
Nitrogen: 8 wt%Phosphorous: 0.3 wt%
Fertilizer Parameters (2-3)
Nitrogen: 23.7 MJ/kgNitrogen: 1.675 kg CO2e/kg Phosphorous: 5.78 MJ/kgPhosphorous: 0.97 kg CO2e/kgNitrous Dioxide: 0.005 g N2O /g N
Energy and GHG emissions
Nitrogen: 0.0017 MJ/MJEtOH 0.11 g CO2e/MJEtOH Phosphorous: 0.000017 MJ/ MJEtOH 0.0026 g CO2e/MJEtOH Nitrous Dioxide: 0.1 g CO2e/MJEtOH
1
(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
Photo-bioreactor systems to be replaced every 5 years; No GHG emissions from drained bioreactors;
Assumptions
Production of Polyethylene (1)
Energy use: 76 MJ/kg GHG emissions: 1.9 kg CO2e /kg
Dimension of the PBR
Length: 50 feetCircumference: 12.6 feetWall thickness: 5~10 mil
Results
Energy use: 0.05 MJ/MJEtOH GHG emissions: 1.3 g CO2e/MJEtOH
2
(1) GREET, ANL
1
2
Ethanol Distribution and Combustion
Assumptions from GREET Model
40% barge: 520 miles 0.54 MJ/ton-mile 40% railroad tanks: 800 miles 0.36 MJ/ton-mile
20% trucks: 80 miles 0.9 MJ/ton-mile
0.0031 g CH4 and 0.0024 g N2O per MJ of ethanol combusted
Results
Distribution: 0.017 MJ/MJEtOH
1.6 g CO2e/MJEtOH Combustion: 0.84 g CO2e/MJEtOH
3
1
2
3
4
Freight Truck Energy Intensity
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 20100
1000
2000
3000
4000
5000
6000
7000
8000
Single Unit TruckCombination Truck
Btu/
ton-
mile
1 mile = 1.6 km1 ton = 0.907 tonnes1 Btu = 1055 J
Air freight energy intensity
1965 1970 1975 1980 1985 1990 1995 2000 2005 20100
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
Btu/
ton-
mile
Freight energy intensity
1965 1970 1975 1980 1985 1990 1995 2000 2005 20100
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
TruckRailWaterPipeline
Btu/
ton-
mile
CO2 Delivery and Water Consumption
Assumptions
Source water pumped from a depth of 100 meters; Water is circulated to the power plant 6 km away;
Reverse osmosis seawater desalination; (1)
No water loss through evaporation.
Results
Water pumping: 0.002 kWh/MJEtOH
Carbonation: 0.00090 kWh/MJEtOH
Water consumption 0.926 l/lEtOH
Reverse osmosis: 9.5×10-5 kWh/MJEtOH
4
(1) National Research Council Review of the Desalination and Water Purification Technology Roadmap; Washington, DC, 2004
1
2
3
4
Ethanol Separation Process5 6 7
Ethanol Separation Process Compression Energy
11
1
in
outadiabatic P
PnRTW
Inputs
P
T
1
HYSYS simulation
Efficiencies
0.055 MJ/MJEtOH
0.051 MJ/MJEtOH
Processes: Vapor Compression Steam Stripping and Distillation5
2
Ethanol Separation Process Evaporation Energy & Molecular Sieve
Eevap mi vH(T)ii
Inputs
wt%
T
HYSYS simulation
Efficiencies
heat exchange
column eff.
0.16 MJ/MJEtOH
0.17 MJ/MJEtOH
Evaporation Processes: Vapor Compression Steam Stripping6
1
2
1
2
7
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 energyU.S. grid electricity 700 g CO2e/kWhe
Process heatNatural gas 50.38 g CO2e/MJEtOH
S2
S3
Electrical energy and heatNatural gas fueled CHP 478 g CO2e/kWhe
Process heat14 hr Natural gas 50.38 g CO2e/MJEtOH
10 hr Solar thermal 0 g CO2e/MJEtOH
Electrical energy and heatNatural gas fueled CHP 478 g CO2e/kWhe
Extra Process heatNatural gas 50.38 g CO2e/MJEtOH
Lifecycle GHG Emissions for 80% and 90% heat exchange efficiencies 0.5wt%~5wt%
DOE target of 40% of the gasoline emission
DOE target of 20% of the gasoline emission
Ethanol wt % from phtobioreactors
g CO2e/MJ Ethanol
Life Cycle Inventory Assessment
Natural Gas + US Grid Natural Gas CHP Natural Gas CHP + Solar Thermal
How does the ethanol concentration and mix of fuels to generate heat and power influence the ability of the system to meet RFS?
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, non-agricultural 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 FibersValerie Thomas, Wenman Liu, Norman Marsolan
Institute for Paper Science and TechnologySchool of Industrial and Systems Engineering
School of Public PolicyGeorgia Institute of Technology
Arundo donax
PerennialGrown for bioenergyHigh yieldLow inputInvasiveness
Kenaf
AnnualGrown for fiberMedium yieldLow input
Bamboo
PerennialWidely grown in ChinaHigh yieldLow inputInvasiveness
Wheat Straw
Agricultural residueNo additional:
- land use- fertilizers- pesticides- irrigation
Northern softwoodBiodiversityCarbon storageLow inputBamboo 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
Wheat straw
Kenaf
Arundo donax
Bamboo
Northern softwood
Deinked Pulp
0 100 200 300 400 500 600 700
irrigation
process water
m3/ton
Preliminary Comparison: Nitrogen Fertilizer
Wheat straw (10%)
Kenaf
Arundo donax
Bamboo
Northern softwood
Deinked Pulp
0 20 40 60 80 100 120
Other
Kengro
GTP
KC China
kg N/ton
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 OnlyMultiple Impact Categories
Net greenhouse gas emissions from each fiber option under a 100-year time horizon
Arun
do d
onax
Kena
f (35
%)
Whe
at st
raw
(10%
)
Recy
cled
fiber
Bam
boo
Nort
hern
softw
ood
-500
0
500
1000
1500
2000
2500
3000
Landfill emissions
Biogenic to mill
Pulping
Transport
Agriculture
Sum total
kg C
O2e
/t p
ulp
Net greenhouse gas emissions from each fiber option under a 500-year time horizon
Arun
do d
onax
Kena
f (35
%)
Whe
at st
raw
(10%
)
Recy
cled
fiber
Bam
boo
Nort
hern
softw
ood
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
Landfill emissions
Biogenic to mill
Pulping
Transport
Agriculture
Sum total
kg C
O2e
/t p
ulp
BiodiversityDriver 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 storageDriver 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