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