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

Homework #7

Goals: In this assignment, youll do the following:

apply Carnegie Mellon Universitys Economic Input Output Life Cycle Assessment (EIO-LCA) tool

to generate and assess an LCI of ink for the HDPE grocery bag; and

read detailed critiques of a published LCA study and determine how this LCA study may have

failed with respect to best practice LCA methods.

Instructions: When you complete the assignment, return to the Week 7 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: This assignment is worth 100 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.

The Economic Input-Output Life Cycle Analysis (EIO-LCA) Tool

Thus far, weve included the manufacture and transport of ink for labeling of HDPE grocery bags within

the system boundary of the HDPE grocery bag LCA model. In this problem, youll use Carnegie Mellons

EIO-LCA tool to generate a rough LCI of the ink required for the HDPE grocery bag, and use these results

to determine if ink production and transport should be included in or excluded from the LCA moving

forward on the basis of simple mass, energy, and environmental cut-off rules.

In your analysis, youll assume the following:

Each 5 gram HDPE grocery bag requires 0.01 ml of ink (to print a logo on the bag)

The density of ink is 1.2 kg/liter

The 2002 producer price of ink is $2 per liter

Go to the EIO-LCA website at http://www.eiolca.net/ and click on Use the tool. Select the US 2002

(428 sectors) Producer model in Step 1. In Step 2, select the Paint, adhesives, cleaning, and other

chemicals sector, then select the printing ink manufacturing sector. In Step 3, use the default value

of $1 million of economic activity, which means youll analyze $1 million worth of output from the

printing ink manufacturing sector.

In Step 4, youll need to select the results categories listed in Table A one at a time. Then, in Step 5, click

run the model. For each result category, observe the Total for all sectors value, which appears in

the second row of the results table. The total for all sectors is the sum of results for all 428 sectors in

the U.S. economy; in other words, this is the LCI total for the selected elementary flow.

Based on your results for all required results categories, fill in the answers in Table A. (3 points for each

correct answer). Enter only the numerical value (i.e., dont enter the units), and use two decimal

places after the decimal separator in your answers (e.g., X.XX).

Table A: EIO-LCA results for $1 million of output from the printing ink manufacturing sector

Category Unit Total for all sectors Question

Energy Total energy (TJ) 17.00 1

Conventional air pollutants:

NOx Total metric tons 2.68 2

PM10 Total metric tons 0.82 3

SO2 Total metric tons 4.94 4

VOCs Total metric tons 1.39 5

Finally, assume that weve set the following cut-off criteria for our HDPE grocery bag LCA. Note that for

exclusion, an input must meet ALL THREE CRITERIA:

1. All inputs that cumulatively contribute less than 1% of the total system mass input can be

excluded

2. All inputs that cumulatively contribute less than 1% of the total system energy input can be

excluded

3. All inputs that cumulatively contribute less than 1% of the total system emissions of NOx, PM10,

SO2, and VOCs can be excluded

To make the cut off determination for ink production and transport, youll need to follow these steps:

I. Open the Week 7 version of the HDPE grocery bag LCA spreadsheet file, which is available in the

Project Files section of the course website.

II. Refer to the combined mass (kg) of the HDPE grocery bag and its required cardboard packaging

on the Scaling tab. Calculate the mass of ink required per bag. Does the ink comprise less than

1% of the total combined mass of the ink, HDPE grocery bag, and cardboard packaging?

0.01 (ml ink/bottle) * 1/1000 (liter/ml) * 1.2 (kg ink/liter ink ) = 1.2E-05 kg ink

(1.2E-05 kg ink)/(5.0E-03 kg HDPE bag + 3.35E-04 cardboard) = 0.22% of total system mass

III. The data in Table B express the primary energy use and pollutant emission intensities associated

with the transport of ink to the HDPE grocery bag manufacturing plant. Assume that the

transportation distance is 1000 km. Based on the intensities in Table B, calculate the primary

energy use and pollutant emissions associated with shipping the mass of required ink (from Step

II) a distance of 1000 km. (3 points for each correct answer)

Table B: Primary energy use and emissions for ink transport (1000 km) 1.2E-05 kg ink/(1000 kg/t) * 1000 km = 1.2E-05 t-km

Flow Intensity Result Question

Primary energy 1.45 MJ/t-km 1.74E-05 MJ 6

Conventional air pollutants:

NOx 0.66 g/t-km 7.92E-06 g 7

PM10 0.03 g/t-km 3.60E-07 g 8

SO2 0.01 g/t-km 1.20E-07 g 9

VOCs 0.05 g/t-km 6.00E-07 g 10

IV. Calculate the 2002 producer price associated with the amount of ink required for a single HDPE

grocery bag. Then, multiply this price by the EIO-LCA results in Table A to determine the total

primary energy use and pollutant emissions associated with producing the ink required for a

single HDPE grocery bag. Enter your answers in Table C. Hint: Note that units of (TJ/million

dollars) in Table A reduces to (MJ/dollar) e.g., 10 TJ/million dollars = 10 MJ/dollar -- and that

units of (metric tons/million dollars) in Table A reduces to (grams/dollar)e.g., 10 metric

tons/million dollars = 10 g/dollar. (3 points for each correct answer)

0.01 (ml ink/bottle) * 1/1000 (liter/ml) * 2 ($/liter) = $0.00002 of ink required

Table C: Total primary energy use and pollutant emissions associated with producing ink for one HDPE grocery bag

Category Result Question

Energy MJ 11

Conventional air pollutants:

NOx g 12

PM10 g 13

SO2 g 14

VOCs g 15

Results for $0.00002 of ink production

Category EIO-LCA Result

Energy 17.00 MJ/$ 3.40E-04 MJ

Conventional air pollutants:

NOx 2.68 g/$ 5.36E-05 g

PM10 0.82 g/$ 1.64E-05 g

SO2 4.94 g/$ 9.88E-05 g

VOCs 1.39 g/$ 2.78E-05 g

V. Add your results from Tables B and C to arrive at the total estimated primary energy use and

pollutant emissions associated with producing and transporting the amount of ink required for a

single HDPE grocery bag.

Category Transport EIO-LCA Ink total HDPE total % Ink

Energy (MJ) 1.74E-05 3.40E-04 3.57E-04 4.47E-01 0.08%

Conventional air pollutants:

NOx (g) 7.92E-06 5.36E-05 6.15E-05 1.62E-02 0.38%

PM10 (g) 3.60E-07 1.64E-05 1.68E-05 2.64E-03 0.63%

SO2 (g) 1.20E-07 9.88E-05 9.89E-05 2.13E-02 0.46%

VOCs (g) 6.00E-07 2.78E-05 2.84E-05 3.84E-03 0.74%

VI. Refer to the primary energy inputs total on the Primary Energy Total tab of the Week 7 HDPE

grocery bag spreadsheet. This total (0.45 MJ) was calculated, in part, by multiplying the mass

quantity of each fuel input from nature by its calorific value. Does your estimated primary

energy use for ink production and transport (from Step V) comprise less than 1% of the total

system primary energy inputs?

VII. Refer to the LCI Results tab of the Week 7 HDPE grocery bag spreadsheet. Observe the

quantities of NOx, PM10, SO2, and VOCs in the LCI. Compare the quantities of each pollutant

you estimated for ink production and transport (from Step V) to the total quantities of each

pollutant in the current system (from the LCI Results tab). Does your estimated pollutant

quantity for in production and transport comprise less than 1% of the total system pollutant

quantity for each pollutant?

VIII. Finally, answer this question (5 points for the correct answer):

Based on the stated cut-off criteria, your answers above, and the data on ink volume, density,

and producer price provided above, can we confidently exclude ink production and transport

from our HDPE grocery bag LCA?

Enter yes or no here Yes Question 16

Are all LCAs created equal?

In 2007, a report titled Dust to Dust: The Energy Cost of New Vehicles From Concept to Disposal

released estimates on the life-cycle energy use of various models of automobiles. Among the reports

findings was the intriguing conclusion that a Hummer H3 SUV has a lower life-cycle energy footprint

than a Toyota Prius hybrid. Unsurprisingly, this claim received a lot of media attention.

First, read the following article, which was one of many that publicized this claim:

http://articles.philly.com/2007-04-04/news/25242308_1_battery-plant-sudbury-fuel-efficiency

After this claim was repeated across the media, two environmental research institutes published

analyses of and rebuttals to the Dust to Dust report. Read both of these analyses by clicking on the

links below.

Peter Gleick, Pacific Institute, 2007, Hummer versus Prius: Dust to Dust Report Misleads the Media and

Public with Bad Science. http://www.pacinst.org/wp-content/uploads/2013/02/hummer_vs_prius3.pdf

Heidi Hauenstein and Laura Schewel, Rocky Mountain Institute, Checking Dust to Dusts Assumptions

about the Prius and the Hummer: Fact-checking using the GREET life cycle model underlines the deep

divide between the Dust to Dust study and all previous scientific work.

www.rmi.org/cms/Download.aspx?id=6655&file=T07-

01_DustToDust.pdf&title=Dust+to+Dust%27s+Assumptions+About+the+Prius+and+the+Hummer

Finally, answer the questions below. Refer to the lecture notes for guidance when answering these

questions.

Question 20: The study was criticized for not disclosing its source of funding. In best practice LCA, how

should the funding source(s) for a study be disclosed? Select the BEST answer below. (10 points)

1. The source(s) of funding should be listed when discussing the target audience in the goal and

scope definition.

2. The source(s) of funding should be discussed in the interpretation step when discussing the

results.

3. The source(s) of funding should be listed when discussing the study initiator in the goal and

scope definition.

4. The source(s) of funding should be discussed in the introduction of the study.

See the lecture notes for Lecture 7, Page 32, where, when discussing the basics of goal and scope

definition, we state that stating clearly the initiator of the study is important so that the target

audience is knowledgeable of the studys source and are free to take into account any special interests

or biases they may perceive.

Question 21: The study contained comparisons intended for public disclosure. Based on the critiques

by RMI and the Pacific Institute, which of the ISO 14040 series of guidelines were not followed? Select

ALL that apply. Note that some of the answers below are intentionally false! (10 points total)

1. Comparative assertions disclosed to the public should ideally be made on the basis of all

environmental impacts, not just energy use

2. Comparative assertions disclosed to the public must only use process-based life-cycle inventory

analysis

3. LCAs with comparative assumptions must undergo critical review by a panel of independent

experts before being made available to the public

4. For comparative assertions, the impact categories and characterization models need to be

scientifically valid and generally accepted

5. Comparative assertions disclosed to the public must explicitly discuss how the public should use

the results of the study

6. Detailed sensitivity analyses are required for comparative assertions disclosed to the public

Throughout this course, weve tried to stress the strict guidance the ISO 14040 series of guidelines

provide for comparative assertions made to the public, which are among the most rigorous of goals for

LCA. If you review the lecture notes, youll see that each of the above correct statements is supported

during the lectures. Answers #2 and #5 were misleading; there is no provision that comparisons must

be made using process-based LCI only nor any provisions that explicitly state how the public should use

the results (it is typically up to the audience to decide how the results will inform their own personal

decisions).

Question 22: The study was criticized for the seemingly low useful lifetime that it applied to the Prius

(109,000 miles and 12 years) compared to the useful lifetime applied to the Hummer H1 (379,000 miles

and 35 years). Which of these following statements best describes what the study may have gotten

wrong as a result of these useful lifetime assumptions? Choose the BEST answer. (10 points)

1. The studys choice of functional unit (ostensibly, a mile of travel) was flawed as a result

2. The studys choice of system boundaries were flawed as a result

3. The studys choices of reference flows for each vehicle option were flawed as a result

4. The studys choice of intended purpose (to compare the energy footprints of different vehicles)

was flawed as a result

Recall from our Lecture 8 discussions of functions, functional units, and references flows that:

The term function refers to the useful service provided by the product or process under study.

(For example, the function of paint is to color and protect a surface.)

The purpose of the functional unit is to quantify the identified functions in a more precise way

that facilitates mathematical analysis. (For example, a functional unit for paint might be to

cover 10 square meters for 10 years.)

The reference flow is the amount of a product required to fulfill the functional unit. (For

example, to cover 10 square meters for 10 years might require one liter of high quality paint. In

other words, the reference flow for high quality paint is one liter per functional unit. )

From these definitions, its clear that the study may have chosen the wrong references flows to meet

their implied functional unit of 35 years and 379,000 miles of transportation services. On the basis of

this functional unit and their specified lifetimes, a reference flow of 1 Hummer would be required but a

reference flow of over 3 Prius vehicles would be required to meet the same functional unit.

Question 23: Which statements below best describe the conclusions of the RMI critique? Select ALL

that apply. Note that some of the answers below are intentionally false! (10 points total)

1. They concluded that the that the unpublished assumptions and inputs used in the Dust to

Dust study seriously hampered independent understanding of the Dust to Dust studys data

sources and modeling methods

2. They concluded that the Dust to Dust contained no valuable information or insights on the

question of life-cycle energy use of transportation vehicles

3. They concluded that errors in simple energy unit conversions the Dust to Dust report

suggested that the studys methodology was flawed

4. They concluded that the results of the Dust to Dust study could not be independently

replicated based on a peer-reviewed, comprehensive LCA model for transportation energy use

5. They concluded that the lack of uncertainty and sensitivity analysis in the Dust to Dust study

invalidated its results

Careful reading of the RMI critique will reveal that answers #1 and #4 were directly supported by the

critique conducted by RMI. Answer #2 is an overreaching statement that is not supported by their

critique, while answers #2 and #5 werent explicitly discussed by RMI.

Specifically, the RMI critique states:

Our check found that, even when we manipulate the GREET model to favor the Hummer as much as

possible, using some of CNWs most controversial assumptions that we could ascertain from their

published documents, the Prius still has a lower impact on the environment. This indicates that the

unpublished assumptions and inputs used by CNW must continue the trend of favoring the Hummer, or

disfavoring the Prius. Since the researchers at Argonne Labs performed a careful survey of all recent life

cycle analyses of cars, especially hybrids, our research underlines the deep divide between CNWs study

and all scientifically reviewed and accepted work on the same topic.

Question 24: The Pacific Institute critique discussed the issue of false precision. What does this

mean? Select the BEST answer below. (10 points)

1. False precision refers to the use of data and assumptions that are not disclosed to the reader

and therefore cannot be critiqued and/or replicated

2. False precision refers to the lack of formal uncertainty analysis on a models results

3. False precision refers to the reporting of data with more significant digits than is appropriate,

which implies more analytical precision than is realistic for an analysis

4. False precision occurs when a study makes specific conclusions based on very large data sets

Careful reading of the Pacific Institute critique will reveal that answer #3 is best supported by their

critique. Specifically, the Pacific Institute critique states:

Extensive data in the form of numbers are presented in the report, always to a higher degree of

certainty and precision than appears warranted often to four or five significant figures. For example,

the lifetime figures for each vehicle model are reported to four significant figures (such as the 34.96

years for the Hummer H1 noted above). The absurdity of this type of false certainty or precision can

be seen in the following: the Mercury Mariner hybrid is reported to last 11.56 years; the Toyota

Highlander Hybrid is reported to last 11.60 years, or 4219 days versus 4234 days. CNW must thus be in

possession of information that supports this precise difference of 15 days. We know of no such

information. As a result, the report is filled with information that appears precise but in fact has little

accuracy.