Life Cycle Assessment:

Modified from:

H. Scott Matthews

Civil and Environmental EngineeringCarnegie Mellon University

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).

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

Components of LCA -3 or 4 I’s

• Inventory• Impact Assessment• Interpretation (and Improvement)

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

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

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

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

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

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

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, …

Simple Example - Tree

SunlightCO2

O2

Wood

Environ- ment

Tree EnergySystem?Water

If we wanted to do a life cycle inventory of a tree, we could draw the boundary in one of several places

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?

Original System

ManufactureSystem Packaging Transport/

Delivery

Energy

Emissions, Cardboard Box Waste

Car Assembly

Part

Energy

Cardboard Manuf.

UnboxedPart

Raw Mats, Energy

Emissions,Waste

BoxedPart

Packaging Takeback System

Manuf.System

PartPackaging

Transport/Delivery

Emissions, (Less?) Cardboard Waste

Car Assembly

Cardboard Manuf.

Unboxed Part

Empty Box

Transp/Logistics

Reused Box

Energy

Emissions

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

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

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

Inventory Process• Iterative• Collect/validate• Matching data with

unit processes/ functional units/etc

• See “sample forms” on pp.16-20 of ISO 14041 PDF.

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?

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

Impact Assessment

• 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)

Resources• http://www.eiolca.net - tutorial on-line

• 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

Check out book:• Environmental Life Cycle

Assessment of Goods and Services: An Input-Output Approach (RFF Press) (Paperback) by Chris T. Hendrickson (Author), Lester B. Lave (Author), H. Scott Matthews; 2006