Soft drinks are commonly packaged in glass, aluminum and polyethylene terephatha

Question

Soft drinks are commonly packaged in glass, aluminum and polyethylene terephathalate (PET) containers. Life cycle inventories on energy consumption, air emissions and solids generation for the three different types of containers are given in Table 1. Note that the container size varies from one type to another. a. What will be a proper functional unit for the comparison of the three containers? b. Using the sample weighting factor method to rank the three types of containers based on the energy requirement, air emissions and solids waste generation. Give a brief justification to your assigned weighting factors. c. List and comments on three major uncertainties in your ranking analysis. If you are going to redo this project, how would you ensure to make a fair comparison of the three types of containers? Additional information which may be needed: 1 US gallon = 3.5 Liter = 128 oz

Explanation / Answer

a) Proper functional unit for comparison is Z and Z should be minimum.

Z = w1 * Energy + w2 * Air Emission + w3 * Solid waste)/Oz

w1 , w2,& w3 are weighing factors.

b)Let all three weighing factors be equal. w1= w2 = w3 = 0.33

For PET

Z = 0.33 *(10.6/64) + 0.33 * (14/64) + 0.33*(116/64)

= 0.055 + 0.072 + 0.598

= 0.798

For Aluminium

Z = 0.33 *(4.7/12) + 0.33 * (5.8/12) + 0.33*(45/12)

= 0.13 + 0.16 + 1.238

= 1.528

For Glass

Z = 0.33 *(6.1/16) + 0.33 * (12.3/16) + 0.33*(396/16)

= 0.126 + 0.254 + 8.168

= 8.548

Based on Energy requirement, Air emission and solid waste Z should be minimum to be good container.

ZPET = 0.798 < ZAluminium = 1.528 < ZGlass = 8.548

So, PET is Rank 1 , Aluminium is Rank 2 & Glass is Rank 3.

c) We had assumed all three weighing factors equal so the three uncertainties are:

i) Energy consumption weighing factor is less.

ii) Air emission weighing factor is equal to energy consumption weighing factor.

iii) Solid waste weighing factor is higher.

We can make w1 = 1 and w2 & w3 =0 and can compare based on energy required for fair comparison. And the three containers can be compared based on energy required.

For PET

Z =10.6/64

= 0.166 MJ/Oz

For Aluminium

Z = 4.7/12

= 0.392 MJ/Oz

For Glass

Z = 6.1/16

= 0.382

ZPET = 0.166 < ZAluminium = 0.392 > ZGlass = 0.382

So, PET is rank 1, Glass is rank 2 and aluminium container is rank 3.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.