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2010 Concrete Sustainability Conference 1 © National Ready Mixed Concrete Association
Life Cycle Assessment of Life Cycle Assessment of PavementsPavementsSensitivity AnalysisSensitivity Analysis
Alex Loijos, [email protected] Akbarian, [email protected]
Sahil Sahni, [email protected] Ochsendorf jao@mit eduJohn Ochsendorf, [email protected]
Concrete
SSustainability
Hub
2010 Concrete Sustainability Conference 2 © National Ready Mixed Concrete Association
Outline:Outline:Outline:Outline:Study Goals
Literature ReviewMethodology
Phases and ComponentsResultsResults
2010 Concrete Sustainability Conference 3 © National Ready Mixed Concrete Association
Why and HowWhy and How
2010 Concrete Sustainability Conference 4 © National Ready Mixed Concrete Association
Problem Statement and Goals
• Concrete:• Most consumed material on earth after water• U S Cement production is the second most GHG intensive industry after steel• U.S. Cement production is the second most GHG intensive industry after steel
• Transportation accounts for 29% of total U.S. GHG emissions. (EPA 2006)• Over 4 million miles of pavement in the US alone
Equal to driving back and forth to the moon 8 times
Problem statement and goals:How do GHG emissions in the pavement life cycle vary under different engineering and policy scenarios and where are the largest opportunities to reduce emissions?
2010 Concrete Sustainability Conference 5 © National Ready Mixed Concrete Association
Literature Review
• Ranges of impact for pavement LCA• Santero, N. J., & Horvath, Arpad (2009). Global warming potential of
pa ements Bristol UK En ironmental Research Letterspavements. Bristol, UK: Environmental Research Letters.
“Because the impact is context-sensitive, there is no single component that can becomponent that can be considered the least or most influential under all circumstances.”
While broader than most studies, does not include:
• Differentiation between asphalt and concrete
• Influence of maintenance• Recycling/End of life
2010 Concrete Sustainability Conference 6 © National Ready Mixed Concrete Association
Methodology
Life Cycle Assessment framework:• System boundary definitiony y• Inventory
• Inputs – energy and materials needs• Outputs – waste and emissions
• Impact Assessment MaintenanceImpact Assessment• Global Warming Potential in CO2e
• Interpretation of the results
F ti l U it
Maintenance
Functional Unit:• 1 m2 of paved surface with 50 year lifetime
Software: GaBi 4 by PE International LCA Boundaries
Use Phase
+ US Construction databaseLCA Boundaries
No capital goods
2010 Concrete Sustainability Conference 7 © National Ready Mixed Concrete Association
Dynamic Model
Identify pavement parameters and life cycle phasesIdentify pavement parameters and life cycle phases
2010 Concrete Sustainability Conference 8 © National Ready Mixed Concrete Association
Phases and ComponentsPhases and Components
2010 Concrete Sustainability Conference 9 © National Ready Mixed Concrete Association
Concrete Pavement
Phases
COMPPONENTS
2010 Concrete Sustainability Conference 10 © National Ready Mixed Concrete Association
Asphalt Pavement
2010 Concrete Sustainability Conference 11 © National Ready Mixed Concrete Association
Materials ProductionMaterials Production
2010 Concrete Sustainability Conference 12 © National Ready Mixed Concrete Association
Binder Extraction and Manufacturing
Raw Material Extraction and Initial
TransformationManufacturing Placement Use and
MaintenanceRemoval,
Recycling, and Disposal
1.6
1.8kg CO2e per kg
Relevant Parameters
• Overlay depth/density
0.8
1
1.2
1.4 • Overlay depth/density• Overlay composition• Facility technology• Fly ash/other substitution
0
0.2
0.4
0.6
0
Bitumen Cement
2010 Concrete Sustainability Conference 13 © National Ready Mixed Concrete Association
Other Materials and Mix Manufacturing
Raw Material Extraction and Initial
TransformationManufacturing Placement Use and
MaintenanceRemoval,
Recycling, and Disposal
Other Materials and Mix ManufactureAggregate:
Diesel fuel energy: 21.1 – 74 MJ/ton, Average: 53 MJ/ton1
Steel Production:• ~20 GJ/ton• GHG emissions: 1.45 kg CO2e per kg
Concrete Mixing:Concrete Mixing:Not energy intensive
Hot Mix:Drying aggregate is the most GHG intensive activity of production life cycle
1- NCSA (1997); Stammer and Stodolsky (1995); NCSA (1997)
2010 Concrete Sustainability Conference 14 © National Ready Mixed Concrete Association
Transportation PhaseTransportation Phase
2010 Concrete Sustainability Conference 15 © National Ready Mixed Concrete Association
Cement Transport Average Distance by Mode
Mode Min Dist Avg Dist Max Dist %Mode Min Dist Avg Dist Max Dist % Share
Trucked
83 km 167 km (1) 322 km 70%
1 Commodity Flow Survey 20072 Imports – Normal: British Columbia SF2 Imports – Extreme: China New Jersey
Barged 0 km 1400 km (2)
5600 km (3)
30%
2010 Concrete Sustainability Conference 16 © National Ready Mixed Concrete Association
Aggregate Transport Average Dist. by Mode
Mode Distance St. Dev. % ShareTruck 50 km 12 km 26%
Extreme Practice
Rail 507 km 25 km 61%Barge 170 km 45 km 13%
From US Commodity Flow Survey 2007
Extreme PracticeCrushed aggregate arriving from British Columbia to San Francisco
From jericoproducts.com
2010 Concrete Sustainability Conference 17 © National Ready Mixed Concrete Association
Barging Efficiency
Barge 1.3 gCO2e per 100 kg-km: Rail 3.4 gCO2e per 100 kg km: Rail 3.4 g
Truck 6.0 g
2010 Concrete Sustainability Conference 18 © National Ready Mixed Concrete Association
Use PhaseUse Phase
2010 Concrete Sustainability Conference 19 © National Ready Mixed Concrete Association
Use Phase Assumptions
Account only for increase or decrease in emissions due to the pavement’s existence
R d hRoad roughness
Fuel consumption
The same attribution goes for albedo and roadway lightingThe same attribution goes for albedo and roadway lighting
2010 Concrete Sustainability Conference 20 © National Ready Mixed Concrete Association
Rolling Resistance
The largest known life cycle GHG contributionTwo effects: Pavement structure and pavement roughnessTwo effects: Pavement structure and pavement roughness
Source: Santero, et al. 2009
ParametersPavement typeTraffic volumeTraffic volumeTraffic compositionBase fuel efficiencyTemperature etc.
2010 Concrete Sustainability Conference 21 © National Ready Mixed Concrete Association
Albedo Effect
Urban heat island effect
Radiative forcing
Trumps heat islandQ: What’s the effect in cold climates?
Trumps heat island effect by ~10 times
• Varies according to:
Source: Santero, et al. 2009
Varies according to:• Pavement type – asphalt or concrete• Pavement age• Specialty whitener chemicals
2010 Concrete Sustainability Conference 22 © National Ready Mixed Concrete Association
Carbonation
• Between 1.4% and 15% of CO2 is reabsorbed, depending on pavement material properties
Source: Santero, et al. 2009
2010 Concrete Sustainability Conference 23 © National Ready Mixed Concrete Association
MaintenanceMaintenance
2010 Concrete Sustainability Conference 24 © National Ready Mixed Concrete Association
Pavement Service Life
Raw Material Extraction and Initial
TransformationManufacturing Placement Use and
MaintenanceRemoval,
Recycling, and Disposal
Service life is highly variable, and strongly effects energy and resource needs throughout 50 year life
Concrete AsphaltExtreme Low 17.5 7Normal Low1 23 13Normal High2 28.5 16Extreme High 50 20
1- Croney 1997, Gharaibeh 2003, Bentz 2001
2010 Concrete Sustainability Conference 25 © National Ready Mixed Concrete Association
ResultsResults
2010 Concrete Sustainability Conference 26 © National Ready Mixed Concrete Association
Normal Sensitivity Range
(kg
CO
2e p
er m
2 )ar
min
g Po
tent
ial (
Glo
bal W
a
Production Life Cycle
Use Phase
Totals
2010 Concrete Sustainability Conference 27 © National Ready Mixed Concrete Association
Use Phase Range
g C
O2e
per
m2 )
min
g Po
tent
ial (
kG
loba
l War
m
2010 Concrete Sustainability Conference 28 © National Ready Mixed Concrete Association
Sensitivity to Maintenance
CO
2e p
er m
2 )in
g Po
tent
ial (
kg
Glo
bal W
arm
Production Life Cycle
Use Phase
Totals
2010 Concrete Sustainability Conference 29 © National Ready Mixed Concrete Association
Conclusions
• Results of LCA are highly dependent on the initial assumptions.
• There are many opportunities across the life cycle for improvement.
• The use phase dominates under any initial conditions.
• Maintenance 2nd largest component and a trade-off with rolling resistance.
2010 Concrete Sustainability Conference 30 © National Ready Mixed Concrete Association
Future Work
• Improve Data Quality• Detailed Scenario Analysis
• 1) Decrease surface roughness by increasing preventive and1) Decrease surface roughness by increasing preventive and rehabilitative maintenance
• 2) Leverage albedo effect and include whitening chemicals in LCI• 3) Engineered Cementitious Composite (ECC), etc.
4) M d l fl h i h k h t• 4) Model fly ash, rice husk ash, etc.• Life cycle costing• Create tool for engineers to
estimate their pavement’sestimate their pavement s carbon footprint
2010 Concrete Sustainability Conference 31 © National Ready Mixed Concrete Association
Thank You!Thank You!Questions?