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
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- Energy CO2 Tree ment
System?
CO2
Tree
Water
Wood
You might also recognize this as a process-flow diagram. Same thing.
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 Energy Raw Mats, Energy Energy Unboxed Part Boxed Part
Cardboard
Manuf.
Energy
Raw Mats, Energy
Energy
Unboxed
Part
Part
Boxed
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 of ISO 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):
BEES (construction materials):
Slightly ahead of schedule in content, but you should look at these for ideas before finalizing ideas and scope for Course Project