Life Cycle Assessment: The ABC’s

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Life Cycle Assessment: The ABC’s. H. Scott Matthews Civil and Environmental Engineering Carnegie Mellon University. Brainstorming Exercise. Break into groups of 5 Draw process flow diagrams for producing 5 products: Can of Coca Cola Steel Water Electricity Coal

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### Life Cycle Assessment:The ABC’s

H. Scott Matthews

Civil and Environmental Engineering

Carnegie Mellon University

Brainstorming Exercise
• Break into groups of 5
• Draw process flow diagrams for producing 5 products:
• Can of Coca Cola
• Steel
• Water
• Electricity
• Coal
• Make them as comprehensive and inclusive as you feel comfortable.
A - 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?
Allocation (cont.)
• Ideally, avoid it
• Separate into subprocesses
• Divide and conquer (only allocate from 1)
• Example: CMU produces 30 CEE graduates per year. How to model student production of the university?
• There are ~30 departments, assume each produces one?
• One of the 30 departments is CEE, and produces all of the graduates
• This sounds trivial, but is a common mistake!

Source: ISO 14041, Appendix B

Allocation Rules (cont.)
• Else expand system boundaries!
• Allocate by physical relationship
• Allocate incinerated waste emissions of cadmium only to waste products containing cadmium
• Mass or volume for transport allocation
• See other examples in ISO 14041, App B

sub-system2

process

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sub-system1

Structure of a Process-based LCA Model
B - The Boundary Issue
• Where to set the boundary of the LCA?
• Include all processes, but at least the most important processes if there are time and financial constraints
• Which are the least and most important?
• Often do not know until you’re done!
• Draw boundaries around processes, number of flows tracked, life cycle stages, time, ..?
• Maybe combinations of the above

RESOURCES

waste

system boundary

C - Circularity Effects
• Circularity effects in the economy must be accounted for: cars are made from steel, steel is made with iron ore, coal, steel machinery, etc. Iron ore and coal are mined using steel machinery, energy, etc...

product

emissions

Special Notes - Public Studies
• Follow ISO-prescribed format on reporting the results
• Use external peer-reviewers to ensure validity
• Incorporate, as necessary, comments of reviewers
• Much like an academic journal publication process!
• Be careful with comparative assertions (i.e., “A is better than B”)
• Cannot just use LCIA results, weighting methods
“Process-based LCA” Tools
• BEES (NIST, construction-oriented)
• NREL LCI (Ongoing)
• Swiss ecoinvent (\$1500)
• http://www.ecoinvent.ch/en/index.htm
• SimaPro (\$2000-\$4000)
• GaBi (\$1000-\$3000)