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Life Cycle Assessment: History and Framework

Life Cycle Assessment: History and Framework. H. Scott Matthews Civil and Environmental Engineering Carnegie Mellon University. Course Comments. Brief (re)-Intros Projects Intended to help you start practicing Will summarize, not repeat, what is found in readings

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Life Cycle Assessment: History and Framework

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  1. Life Cycle Assessment:History and Framework H. Scott Matthews Civil and Environmental Engineering Carnegie Mellon University

  2. Course Comments • Brief (re)-Intros • Projects • Intended to help you start practicing • Will summarize, not repeat, what is found in readings • Make sure you know ‘definitions’ from ISO documents

  3. Life-Cycle Assessment (LCA) • A concept and methodology to evaluate the environmental effects of a product or activity holistically, by analyzing the whole life cycle of a particular product, process, or activity (U.S. EPA, 1993). • LCA studies analyze the environmental aspects and potential impacts throughout a product's life cycle (e.g., cradle-to-grave) from raw material acquisition through production, use and disposal (ISO).

  4. LCA Uses • Process analysis • Material selection • Product evaluation • Product comparison • Policy-making • Measuring performance • Marketing

  5. Components of LCA -3 or 4 I’s • Inventory • Impact Assessment • Interpretation (and Improvement) • We’ll do a lot with #1, then #2, and come back to #2 at end of course • Regardless, need to learn terminology first before doing anything else..

  6. Components and Criteria • Criteria: • Spatial, Temporal • Design • Functional unit • Significance/magnitude • Uncertainty • ISO documents a framework (not a recipe); LCAs may or may not consider all points above

  7. Criticisms / Limitations • Data reliability and quality is questionable. • Models based on assumptions. • Problem boundaries are arbitrary. • Scale issues - global -> local, etc. • Uncertainty is everywhere • Spatial and temporal issues • Comparisons between studies difficult • No single, accepted method

  8. Important Note on Context • LCA should be one part of a broad environmental assessment • If comparing with LCA, all assumptions and methods should be consistent • Especially problematic for validating against external studies

  9. Definitions • Big set of definitions in ISO framework documents (e.g., p.1 of ISO 14040) • Won’t review all of them here, but you need to know them. • Big ones to know are unit process, elementary flows, inputs, outputs

  10. Definitions • Elementary flows - material or energy entering or leaving the system, directly to/from the environment, without human transformation • Unit process - smallest portion of a product being studied for which LCI data available • Inputs / Outputs - materials or energy entering or leaving a unit process

  11. Scope Considerations • Setting all the parameters for study • e.g., functional unit, boundaries, data, etc. • Whether it will be critically reviewed • May be iterative (update in progress) • Supports product system diagram • Realize LCA can be used for ‘products’, ‘processes’, ‘systems’, etc. • Functional unit definition ensures unit consistency for validation and comparison

  12. Product Systems • Collections of unit processes, elementary flows, and product flows • Also shows system boundary • Processes, flows maybe in / out of bounds • In: fuel, energy, materials, … • Out: emissions, waste, …

  13. Simple Example - Tree Sunlight O2 Environ- ment Energy System? CO2 Tree Water Wood If we wanted to do a life cycle inventory of a tree, we could draw the boundary in one of several places

  14. More Complex Example • We manufacture a part for new automobiles and ship it in cardboard boxes • Currently, we “ship and forget it” • Generates significant box waste • We want to reduce waste - how? • What are tradeoffs?

  15. Original System Cardboard Manuf. Energy Raw Mats, Energy Energy Unboxed Part Boxed Part Part Manufacture System Transport/ Delivery Car Assembly Packaging Emissions, Waste Emissions, Cardboard Box Waste

  16. Packaging Takeback System Energy Cardboard Manuf. Reused Box Transp/ Logistics Emissions Part Manuf. System Packaging Empty Box Transport/ Delivery Car Assembly Unboxed Part Emissions, (Less?) Cardboard Waste

  17. Packaging Takeback System • Our new system uses less cardboard • Thus less waste, manufacturing impacts • But uses more transportation to retrieve used boxes • Thus more energy use, emissions • Unclear whether this tradeoff is beneficial • Perfect application for LCI/LCA

  18. Example Goal/Scope • Goal: “To determine whether the new system is better than the old” • More detail: which inventory items? How to assess? • Maybe air emissions, energy use, waste generated • Would a better goal originally have been to do LCA of old system and suggest improvements? • Scope: Fairly detailed description of both systems, items in/out of boundaries • e.g., might exclude impacts of product (relevant?) • But include packaging/logistics/reuse of systems

  19. Next Step: Inventory • In general, just “good research” • “Look up the data, add it up” • However, data availability varies widely • Consider inputs, outputs of interest • In: energy, resources, etc. • Out: emissions, waste, etc. • Also may be iterative • Allocation an issue

  20. Inventory Process • Iterative • Collect/validate • Matching data with unit processes/ functional units/etc • See “sample forms” on pp.16-20 of ISO 14041 PDF.

  21. Allocation • Hard to assign “one to one” linkages between units and inputs-outputs • Need standard/specified way to distribute (allocate) them • mass balance method • Physical properties • Economic value ratio? • What allocations needed for packaging takeback system?

  22. Inventory Interpretation • How do results fit goal/scope? • Assessment of data quality • Sensitivity analysis on inputs/outputs

  23. Data Sheet Exercise • Break into small groups (2-3 max) • Using samples provided (from ISO 14041) summarize data for: • Getting to school • Doing a homework assignment / writing a paper • Reading a book chapter • Something else similar

  24. Impact Assessment • We’ll come back to this later in course • Classification • Characterization • Weighting (e.g. taking an inventory of various toxics, then weighted by toxicity) • Assumed that existing weighting methods can be used (not developed as part of LCA)

  25. Resources • Don’t despair, you do not need to collect all of your own data for LCAs, for example: • US NREL LCI Database (various): http://www.nrel.gov/lci/ • BEES (construction materials): http://www.bfrl.nist.gov/oae/software/bees.html • Slightly ahead of schedule in content, but you should look at these for ideas before finalizing ideas and scope for Course Project

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