Study Approach Well examine pavement materials as a case study of - PowerPoint PPT Presentation

A C RITICAL R EVIEW O F L IFE C YCLE A SSESSMENT (LCA) P RACTICE F OR I NFRASTRUCTURE M ATERIALS Alissa Kendall Assistant Professor, Civil and Environmental Engineering, University of California, Davis John Harvey Professor, UC Pavement Research Center and Civil and Environmental Engineering, University of California, Davis In-Sung Lee Doctoral Candidate, UC Pavement Research Center and Civil and Environmental Engineering, University of California, Davis

Study Approach  We’ll examine pavement materials as a case study of LCA applied to infrastructure materials  Highlight many of the challenges and shortcomings we face when conducting LCAs  Make recommendations for improving transparency and reducing variability across studies

Study Approach  We use the primary LCA steps as outlined by ISO/SETAC/EPA for process-based LCAs as the framework for evaluation  Examine key problems or challenges at each stage  Not an exhaustive review of the literature or challenges, but intended to initiate discussion

Infrastructure Material Life Cycle Infrastructure Life Cycle Material Life Cycle Equipment Pavement RawMaterial emissions, conditioneffects Acquisition traffic Delay on fuel economy  Infrastructure T materials must Processingand Manufacture be considered in T the context of End-of- Construction / Infrastructure T Use their application. Life Rehabiliation Materials T Rehabilitation frequency = f ( material and design performance, End-of-Life use-phase loading, etc. ) T MaterialRe-use/Recycle T= Transporation

Three Key Elements of Life Cycle Assessment Establish the system to be evaluated (design, location, etc.) Goal and the boundaries of Definition and the study. Scope At each stage sources of uncertainty and Interpretation inputs to and variability are outputs from the Life Cycle introduced. system are assessed Inventory and assembled Assessment LCI are translated into relevant impacts on humans Impact and the Assessment environment Figure based on ISO 14001

Variability and Uncertainty in LCA Goal & Scope Life Cycle Impact Definition Inventory Assessment Variability and Uncertainty in Temporally Static Life Cycle Models Design Population decisions, density and Uncertainty construction susceptibility, and variability variability, ecosystem in LCI traffic and climate Datasets loading, sensitivity, climate, etc. etc. Variability and Uncertainty in Temporally Dynamic Life Cycle Models Changes in Changes in Infrastructure population production performance, density, and resource budget-based background availability, decisions, emissions, novel maintenance environmental materials and practices, etc. and climate technologies conditions, etc.

Three Key Elements of Life Cycle Assessment Goal Definition and Scope Interpretation Life Cycle Inventory Assessment Impact Assessment Figure based on ISO 14001

Goal and Scope Definition  Purpose of study o Comparative vs. Baseline  System Boundary o What life cycle stages are considered? o What processes from each life cycle stage are included in the study?

Comparison of Scope for Five Pavement LCA Studies 4 of 5 studies compare asphalt and concrete Treatment of Uncertainty / Author Year Scope Key Findings for GHG emissions Sensitivity Pavement construction, and materials Asphalt better for CO 2 emissions, and Some sensitivity to timing of comparison of asphalt and concrete over 40- results are dominated by construction construction (e.g. best/worst Stripple 2001 years. Traffic not considered except in a emissions. Lighting and traffic control scenarios). Also tested traffic sensitivity analysis are important. flow. Asphalt pavement system that considers This is a baseline study for Korean Park et al 2003 earthwork along with other construction and roads. Assumes an asphalt pavement None rehabilitation activities, 20-year time horizon system only - though this is not clear Scenario analysis for different For 100% virgin asphalt systems, Comparison of portland cement concrete and roadway types and capacities, Athena concrete had lower CO 2 e* emissions. Institute 2006 asphalt concrete roadway designs, subbase also 0% and 20% recycled For 20% recycled asphalt content, included, 50-year time horizon asphalt content in asphalt asphalt slightly better mixes Overlay: Contruction, materials, and traffic Zhang et ECC best, then concrete, then asphalt 2007 over a 40-year service life for asphalt, Sensitivity to traffic growth rate al for CO 2 e emissions concrete and ECC Asphalt pavement performs better on Asphalt pavement and concrete pavement Evaluated low-emission and Chiu et al 2008 CO 2 emissions as well as all other (40-year life cycle), materials, construction normal vehicles energy and emissions categories Only two studies consider Asphalt better for Concrete better for the use-phase. But they Greenhouse gas Greenhouse gas don’t consider the same (GHG) emissions (GHG) emissions use-phase process!

The Pavement Use-Phase  The two studies that considered use-phase processes in their LCA found they were influential  Important uncertainties not fully addressed in current LCAs o Pavement-vehicle interactions • Though studies have begun to consider this (e.g. Zhang et. al) our understanding of what the fuel economy effect of pavement surface characteristics is not sophisticated

Three Key Elements of Life Cycle Assessment Goal Definition and Scope Interpretation Life Cycle Inventory Assessment Impact Assessment Figure based on ISO 14001

Uncertainty in LCI Datasets  LCA studies rely on life cycle inventory datasets. These datasets are compiled by firms and public entities based on real data from specific facilities, average data from many facilities, or engineering calculations  The time horizon over which data are collected, the year the data is collected, and of course the location of collection may all influence the LCI dataset

Uncertainty in Pavement Datasets  To reduce the differences in datasets due to variations in mix design, we examine datasets for the primary binders used in asphalt (bitumen) and concrete (cement).  These datasets are derived from reports and databases accessed through a widely-used LCA software tool (Simapro)

GHG emissions per kg bitumen 500 400 CO2e (kg) 300 200 100 0 Stripple ETH-ESU 96 Ecoinvent

GHG emissions per kg cement 1200 1000 800 CO2e (g) 600 400 200 0

Three Key Elements of Life Cycle Assessment Goal Definition and Scope Interpretation Life Cycle Inventory Assessment Impact Assessment Figure based on ISO 14001

Uncertainty and Variability in Impact Assessment  Lots of uncertainty and variability o Uncertainty • How do pollutants effect ecosystems, people, climate, etc. o Variability • The effect of a pollutant varies due to many factors such as background emissions, population density, ecosystem sensitivity, and timing  Here we examine greenhouse gas (GHG) emissions timing only o Timing and/or location are important for all pollutants however

What does CO 2 e mean? • Global warming potentials convert non-CO 2 GHGs to CO 2 equivalent (CO2e) This stage is called cumulative Impact Chain for Global Warming radiative forcing Increase in radiative forcing (RF) (CRF) Global Warming A build up of heat due to RF over some time Potentials Atmospheric warming Eventual Temperature Change Climate Change

How GWPs are Calculated TH Note: RF is dynamic RF dt i for all GHGs of 0 GWP concern, since i TH , TH concentration is RF dt CO 2 constantly changing! 0 • TH = Time Horizon • 100 years is a common time horizon • IPCC also reports 20, and 50 year time horizons

The Impact Chain: GHGs  Most LCAs (and most new legislation) rely on the IPCC estimates for global warming potentials (GWPs) to convert non-CO 2 GHGs 100 year to CO 2 e time horizon  CO 2 GWP 100 = 1  CH 4 GWP 100 = 25 GWP 20 = 76  N 2 O GWP 100 = 296  We typically just sum up GHGs over the time horizon of study

What does this mean for how we model CO2 in the Atmosphere? Imagine an emission that occurs in year one with a value of 1. 1.2 Then imagine if this value is 1-unit Pulse 1-unit Pulse Emission occurs spread out over 20 years (e.g. CO2 in Atmosphere (unitless) emission in year 1 emission in year 1 1 all in one year 1/20 emitted each year) 0.8 0.6 0.4 Emission spread Amortizedemissions Amortizedemissions 0.2 out over 20 years (1 unit/20) (1 unit/20) 0 Year 0 20 40 60 80 100 120

How does this change modeled CRF? 0.0008 0.0007 CRF (W/m2 *years) 0.0006 0.0005 0.0004 Pulse emission 0.0003 in first year 0.0002 Emissions Amortized over 20 emission 0.0001 years (TH=20) 0 Years 0 20 40 60 80 100

CRF Based on Athena Institute Study  Compared asphalt and concrete over 40-year time horizon  Assumed asphalt would need to be replaced at year 20, but concrete would not  Results showed no demonstrable differences between global warming effects (represented as CO 2 equivalent) between to the two designs