How Green is That Product? An Introduction to Life Cycle Environmental Assessment

Homework #4: Part 1 Solutions

Correct answers in RED

Goals: In Part 1 of this assignment, youll evaluate a published LCI report to do the following:

identify key goal and scope definition elements; and

interpret life-cycle inventory results.

Instructions: The questions below can be answered offline. When you complete the assignment, return

to the Week 4 course page on the Coursera website. Click on the Submit Homework Assignment

Answers button, which will allow you to enter your answers into a web form for automated grading.

Grading: Part 1 of Homework #4 is worth 45 points. The point values of each answer are listed below.

You can submit a maximum of 30 attempts. The highest scoring attempt that is submitted before the

deadline will count toward your official grade. Scores for each attempt will be available immediately

after submission of your answers.

Numbers: In this assignment, and throughout this course, numbers will be expressed using the U.S.

numeric convention where commas separate thousands and the dot (or decimal point) is the decimal

separator. For example, the number one thousand two hundred and one-tenth is written 1,200.1.

Identifying study definitions and conclusions (5 points each answer)

To answer these questions, youll need to download the following report by clicking on the link:

Franklin Associates (2009). Life Cycle Inventory of Three Single-Serving Soft Drink Containers: Revised

Peer Reviewed Final Report. Prepared for the PET Resin Association. Eastern Research Group. Prairie

Village, KS. http://www.container-recycling.org/assets/pdfs/LCA-SodaContainers2009.pdf

Specifically, review the executive summary and the study description and assumptions in Chapter 1.

Then, answer the following questions:

Question 1: What is the stated purpose of this study?

To determine the optimum waste management strategies for non-refillable single-serving soft

drink containers.

To evaluate the resource use, solid wastes, and greenhouse gas emissions associated with

common containers used for non-refillable single-serving soft drinks.

To promote the superiority of PET containers for use as non-refillable single-serving soft drinks.

To guide consumer decisions on single-serving soft drinks.

The stated purpose of this study can be found on page ES-1. If you looked closely, youll have noticed

that another stated purpose appears on page 1-1, which is slightly different than the stated purpose on

page ES-1! Given the options weve provided above, the best answer is the second option, based on

page ES-1. However, note that it is important to make one clear and consistent statement of purpose in

your own LCAs as a matter of best practice.

Question 2: Who is the intended audience of this study?

The LCA research community.

The general population of consumers.

The member companies of PET Resin Association.

Public policy makers.

This study has indicated that member companies of PETRA are the key audience for the LCI on pages ES-

1 and 1-1.

Question 3: What is the functional unit of this study?

One non-refillable single-serving soft drink container.

One bottled soft drink.

The primary packaging of 100,000 ounces of soft drink.

8,333 aluminum cans, 12,500 glass bottles, and 5,000 PET bottles.

Recall that the functional unit provides a precise and measurable description of a products function,

which also serves as the basis of comparison for different product options. Once one defines the

functional unit that describes the service being provided to the consumer, one can select the reference

flows necessary for different product options to provide one functional unit of service. In this study, the

functional unit is stated clearly on pages ES-2, 1-2, and elsewhere throughout the report.

Question 4: What reference flows are chosen to meet the stated functional unit of this study?

One non-refillable single-serving soft drink container.

100,000 ounces of soft drink.

One bottled soft drink.

8,333 aluminum cans, 12,500 glass bottles, and 5,000 PET bottles.

The authors dont use the term reference flow when stating the quantities of different product

options that will satisfy the functional unit in their study. Rather, they directly state on page ES-2 To

package 100,000 ounces of soft drink, the analysis considers the production of 8,333 aluminum cans,

12,500 glass bottles, and 5,000 PET bottles. Based on your understanding of reference flows, and their

relation to the functional unit in an LCA, this statement should have led you to the correct answer to this

question, which is option d. Note that the casual analyst may have chosen to directly compare one

aluminum can, one glass bottle, and one PET bottle, but that analyst would have been making an unfair

comparison because different volumes of soft drinks would have been compared due to the different

volumes of the containers!

Question 5: Which category accounted for the largest share of total energy requirements for the three

different types of container?

Process energy.

Transportation energy.

Energy of materials resource.

As seen in Figure ES-1, process energy represents the largest share of the total energy requirements in

the life cycles of all three types of container. As noted on page ES-6, process energy includes all energy

used to extract and process raw materials into usable forms, manufacture the container systems, and

manage postconsumer materials.

Question 6: Which statement is correct?

PET containers have the highest transportation energy, followed by glass, then aluminum.

Glass containers have the highest transportation energy, followed by PET, then aluminum.

Aluminum containers have the highest transportation energy, followed by glass, then PET.

Glass containers have the highest transportation energy, followed by aluminum, then PET.

As seen in Table 2-1 of the report, the correct answer here is the fourth option.

Question 7: From which year are the inventory data for production of the PET resin?

2009

2003

2006

1997

To answer this question, one has to dig into the assumptions for the life-cycle inventory data that were

documented in the report. On page 1-5, the report states for the PET bottle system that: LCI data for

the production of nine commodity plastics were collected for the year 2003 by Franklin Associates from

producers in North America.

Question 8: From what geographic region are the inventory data for production of the PET resin?

Europe

Europe and North America

United States

North America

To answer this question, one has to dig into the assumptions for the life-cycle inventory data that were

documented in the report. On page 1-5, the report states for the PET bottle system that: LCI data for

the production of nine commodity plastics were collected for the year 2003 by Franklin Associates from

producers in North America. This data collection effort was sponsored by the member companies of the

Plastics Division of the American Chemistry Council and represents the most recent LCI data for plastics

production in North America. This analysis uses these data for modeling the production of PET and

polypropylene. These data are publicly available through the US LCI database (www.nrel.gov/lci).

Please note that the US LCI Database is just the name of the database in which the resin data can be

found. However, the name of the database should not be confused with the geographic origins of all

data contained in that database.

Question 9: What process technology is assumed for the manufacture of PP closures?

Blow molding

Biaxially-oriented extrusion

Injection molding

On page 1-5, the report states that: PP closures in the PET bottle system are assumed to be made from

polypropylene resin, which is fabricated by injection molding. Recall that it is important to state the

technologies associated with an inventory so that the analyst and audience can assess the technology

correlation between the chosen LCI data and the stated goals of the study.