pavements and the environment

1. Pavements and the Environment Nicholas Santero, Ph.D. Postdoctoral Scholar Civil and Environmental Engineering University of California, Berkeley

3. Life-Cycle Assessment (LCA) Used to quantify “cradle-to-grave” environmental impacts of a system Begins with upstream supply chain and ends with ultimate decommissioning Measures inputs and outputs over the life cycle Example inputs: energy, water, resources Example outputs: air emissions, water emissions General standards set by ISO 14040 series Provides general LCA guidance, but lacks detailed information for individual processes

4. The Pavement Life Cycle

5. The Pavement Life Cycle

6. Focus of Existing LCA Research

7. Traffic Delay Caused by construction activities Idling and stop-and-go traffic reduce fuel economy Occurs during initial construction and maintenance phases Impact is related to project details, e.g., Traffic level Time of day Closure configuration Software available to estimate traffic delay Primarily for LCCA purposes, but can be adapted for environmental assessments e.g., CA4PRS, RealCost

8. Carbonation Natural carbon cycle CO2 released during calcination of limestone is recaptured over time Time for appreciable sequestration is often long Measured in decades, centuries, or even millennia Sequestration rate can be expedited through strategic design and management techniques Concrete properties affect carbonation rate Crushing and exposing concrete to the atmosphere can quickly recapture large amounts of carbon

9. Lighting Lighting provides necessary illumination for certain roadways Requirements vary by pavement classification Pavement surface characteristics can affect the light needed for proper illumination In general, darker pavements require more lighting than do lighter pavements, resulting in higher electricity demand More efficient lighting technologies (e.g., LEDs) will reduce the energy disparity between light and dark pavements

10. AlbedoUrban Heat Island Pavements absorb incomingradiation and release as heat Result is a rise in urban temperatures, resulting in increased electricity demand via air conditioning Location specific effect Dense urban environments High-temperature cities Incremental effects not well studied Current research focuses on large metropolitan areas What is the marginal effect of a single unit of pavement?

11. AlbedoDirect Radiative Forcing Pavements directly affect the earth’s energy balance Higher albedo pavements reflect more radiation back into space Reflected radiation can be measured in CO2 equivalent (CO2e) units Very little research on this topic Primarily studied by researchers at Lawrence Berkeley National Laboratory Exact numerical relationship between albedo and CO2e not well defined

12. Fuel ConsumptionPavement Roughness Pavement roughness is linkedto fuel consumption Multiple studies have confirmed the relationship, but a definitive numerical model is unavailable Current roughness metrics (e.g., IRI) may not be best indicators of fuel consumption Ideal stopping distance and rolling resistance properties can be achieved simultaneously Texture wavelengths responsible for rolling resistance are separate from those providing friction

13. Fuel ConsumptionPavement Structure Structural properties influencefuel consumption High stiffness pavements offer better fuel economy, but exact relationship is unknown Probably more significant for heavy vehicles Not necessarily a concrete versus asphalt issue Structures built with thick asphalt and stiff base layers offer similar deflection characteristics to concrete Assessments should be based on the entire structure, not just the surface material

14. Leachate Pavements contain heavy metals and PAHs In general, the literature refutes that pavement materials pose a significant water quality problem Much of the runoff quality issues stem from traffic-based pollutants, such as vehicle exhaust, lubrication oils, fuels, and tire particles Specialty applications present higher risks Recycled pavements contain high concentrations of traffic-based pollutants Asphalt sealcoats have been shown to produce high levels of PAHs, especially after the “first flush”

15. Global Warming PotentialRanges of Impact for Life-Cycle Components

16. Reducing Carbon Footprints Multiple ways to reduce carbon emissions Most effective solutions not necessarily the most obvious e.g., focusing on materials production is often not the most efficient method of improvement Different pavement locations, characteristics, and other details govern best-practices No “one-size fits all” solution

17. Global Warming PotentialHigh- versus Low-Traffic Scenarios

18. Measuring PerformanceEnvironmental Inventories in Existing LCAs Pavements are commonly compared by their energy consumption However, no consistency regarding the inclusion of asphalt’s feedstock energy Air emissions (CO2, NOX, etc.) captured by roughly half of the studies Other environmental metrics not well inventoried, e.g., water consumption water releases toxic releases

19. Measuring PerformanceImpact Assessment Impact assessment improves understanding of inventory results Categories include human health, ecotoxicity, acidification, ozone depletion, and others Most pavement LCA rely on inventory results for conclusions Often not appropriate to aggregate impacts into a single score Weighting of impacts requires value choices, which change based on agency objectives and project scenarios

20. Policymaking No silver bullet Each pavement presents its own unique challenges are opportunities for environmental improvement The most cost effective solutions will not be same for each pavement Focus on efficient reduction schemes Small changes in high-impact components will have a greater effect then large changes in low-impact components Identify which environmental metric(s) are important to the agency or institution Policy decisions may improve certain metrics while degrading others

21. Next Steps Address research gaps in life cycle The use phase is particularly unexplored Efforts underway to develop more precise models (e.g., MIRIAM Project) Expand scope to include alternative metrics Energy and global warming are relatively well studied Water consumption, toxicity, and other impact areas deserve more attention Develop environmental policy based on LCA research Existing knowledge is sufficient to create general policies and roadmaps for improving environmental performance

22. Acknowledgments