Life Cycle Assessment: The ABC’s

1. Life Cycle Assessment:The ABC’s H. Scott Matthews Civil and Environmental Engineering Carnegie Mellon University

2. 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.

3. 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?

4. 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

5. 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

6. sub-system2 process process process process process process process process process process process process process process process process process process process process process sub-system1 Structure of a Process-based LCA Model

7. 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

8. 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

9. 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

10. “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) • Links on Website

11. Data Sources - Heart of Tools • All of these tools are ‘front ends’ to databases • The data is the important part • The interface is just there to help • Should examine data documentation to guide you towards what you need

12. Reporting • Need to document everything you’ve done, especially assumptions. • See ISO 14041 document (Section 8)