ME 4171 – Environmentally Conscious Design and Manufacture
Final Exam – March 16, 1998
Total 180 points
1 – Some General Questions (3 points each)
(60 points)
a) A paper towel manufacturer advertises that their product is made of 100% recycled materials.
Without any further claims, what could they be hiding about their claim?
b) An auto manufacturer claims that one of their cars is 90% recyclable. What might they not
be telling you that weakens their seemingly strong claim?
c) What is the difference between toxic waste reduction and waste minimization?
d) Name five reasons why products become obsolete.
e) What is ISO 14000?
f) What are the trends in material use?
g) What are the pros and cons of selling product utilization versus selling products per se.
h) What is the difference between pre-consumer scrap and home-scrap.
i) What are the EPA’s Life-Cycle Design goals?
j) What are key differences between manufacturing and remanufacturing.
k) Name at least three common measures of useful product life.
l) In which four categories can environmental impact be organized, according to the EPA.
m) Briefly discuss design strategies for reducing environmental impact.
n) Why do some people argue that hydro-electric power is not environmentally friendly?
o) What are the differences between pollution prevention and design for the environment?
p) Name two ways that shredded copper bits can be separated from plastics (besides through
manual separation by a human)?
q) List two ways that reducing the weight of a product can increase the environmental
friendliness of that product.
r) What are the advantages/disadvantages to having a single metric (one number) that represents
the complete life cycle environmental friendliness of a product?
s) Why is separability a key issue in recycling?
t) Name at least four drivers for why industry is pursuing Environmentally Conscious Design
and Manuacture?
1
2 – Sheet Molding Compound Manufacture
(30 points)
Sheet Molding Compound (SMC) is a fiberglass-resin compound which is molded into products
ranging from Jet-Ski hulls to valve covers and micro-wave dishes.
Resining
Mixing
Paste
Paste
Combination
Compaction
Figure 2.1 - SMC Manufacturing Process
SMC is manufactured by placing a layer of paste on a sheet of carrier film, dropping a layer of
randomly oriented glass fibers one to two inches in length on this layer of paste, and adding a
layer of paste on top of this (Figure 2.2). This paste-glass combination then passes through a
compaction section to ensure that the fibers are "wetted out", or covered with paste. The SMC is
then stored for two days to cure the plastic. At this point it is cut into charges, or shaped pieces
of the sheet, and placed in a heated mold. Pressure is applied, hardening the SMC into the
desired shape.
Paste
Fiberglass
Paste
Figure 2.2 - Pre-compaction SMC
While the fiberglass is simply bought from a supplier in roll form, the paste is manufactured in
the plant, and can have many different formulations. The paste formulations are based on liquid
resins to which filler and other materials are added. These resins are manufactured elsewhere,
brought to the plant, and stored in large holding tanks. These tanks are connected through pumps
to a resining station. Portable tanks are brought to this station, filled with resin or with styrene,
and taken elsewhere in the plant for the mixing process (Figure 2.3).
2
From Holding Tanks
Screen
2 feet
Portable Tank
(Approx. 4 ft. diameter)
Figure 2.3 - Resining Station
During the mixing process fillers (such as silica) are added to the paste to increase its volume,
essentially cutting the strength of the resin. After mixing, the tank is taken to a pumping station.
Here the paste mixture is emptied from the tank into a pumping system that mixes the paste with
a catalyst. This begins the SMC "curing" process, and the paste must quickly be laid down with
fiberglass as discussed before.
Styrene is a monomer that is an integral component of the resins. It is also stored in pure form in
these tanks since it is used as an inert ingredient to reduce the potency of the resins. Evaporation
of styrene occurs at room temperature and atmospheric pressure from the paste or resin at all
stages of the SMC manufacturing process. Since the tanks are not covered, styrene escapes into
the plant workers environment whenever a tank contains resin or paste. Inhalation of styrene in
sufficient quantities can cause central nervous system damage, and aspiration of styrene can be
fatal. Short term exposure limit for styrene exposure as set by OSHA is 100 parts per million of
styrene. The highest allowable time weighted average (average exposure over an eight hour day)
is 50 ppm.
a)
b)
c)
d)
e)
Draw a process diagram for the preceding process. (5 points)
Create a mass balance for each of the production stages. (10 points)
Identify pollutants. (5 points)
Where would you find the exposure limits for styrene, if it was not given? (3 points)
Identify equipment design options for reducing the release of styrene to the atmosphere from
the process stages and discuss their pros and cons. (10 points)
f) Identify and discuss options for pollution prevention specifically for this process. (10 points)
3
3 – Fork Life Cycle
(25 points)
Consider the simplified product life cycles (given below) of a plastic fork (made out of polypropylene (PP)) and that of a steel metal fork to be used in a restaurant.
Energy 1
ore
Energy 3
Energy 2
fabricate
(press from sheet metal)
package and ship
use
Metal Fork
clean and
reuse fork
dirty water
Energy 4
Energy 1
oil
fabrication
(injection mold)
Energy 2
package and ship
use
Plastic Fork
recycle fork
The following assumptions can be made:
1. A plastic fork weights 50 grams. A metal fork is twice as heavy.
2. The packaging is the same for both forks
3. The shipping distance between the forks' factory and restaurant is 500 kilometers and the
forks are shipped by truck.
4. Anything not shown in the life cycle diagrams is equal between the two options and should
not be considered in comparisons.
5. 100% of plastic forks are recycled directly into new forks
6. Once a metal fork begins being used, it can be cleaned and reused indefinitely.
7. Plastic or metal forks are both acceptable in this restaurant
a) According to the AAMA, what is the difference between reuse and recycling? (3 points)
b) Using the Eco-Indicator tables attached to the exam, what is the difference in environmental
impact in terms of milli-points for the two forks, if we ignore the impact of the cleaning and
dirty water for the metal fork? Justify your assumptions made (if any). (10 points)
4
c) Which of the two options (plastic or metal forks), would the environmentally conscious
restaurant owner use? Why? Consider as many factors as possible and analyze the tradeoffs. (5 points)
d) Narratively, describe how you would go about quantitatively assessing the impact of the
metal fork cleaning process. (4 points)
e) What are two things that are unrealistic about assumption #5? Why might a “generous”
assumption like that be made? (3 points)
4 – Coffee Maker Recyclability
(30 points)
Below is a partially filled out recyclability assessment table for an automatic coffee maker.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Name
Filter basket
Decals
Screws in filter basket holder
Filter basket holder
Top of tank
Aquaduct
Spring from pump
Metal harness from pump
Pump
Rubber stoppers from base
Screws from base
Wires
Base and heating plate
base heating element
On/off switch
Power cord
Screws holding heating element
Heating element, gasket, clamp
Outer housing
Quantity
1
2
4
1
1
2
1
1
3
4
5
5
2
1
1
1
2
1
1
Material
Unit Mass Total Mass R.R. S.R. Recyclable Mass
PP
75.5
75.5
1
Adhesive
0.5
1
2
Steel
0.7
2.8
2
PP
24
24
1
PP
145
145
1
PP
12.5
25
1
Aluminum
4
4
1
Aluminum
6.3
6.3
1
Aluminum, plastic
4.1
12.3
1
Rubber
1.7
6.8
3
Steel
1.3
6.5
2
Copper, rubber
4.3
21.5
2
Aluminum
146
292
1
Nylon, tungsten
25
25
1
ABS
7.6
7.6
1
Copper, rubber
35
35
1
Steel
1.4
2.8
2
Mixed components
146
146
2
PP
645
645
2
1484.1
RECYCLABILITY (BY WEIGHT):
a) What is the difference between the European standards for recyclability and the US Federal
Trade Commission standards? (3 points)
b) Fill in any blanks in the above table and calculate the current and technical feasible
recyclability (by weight) using the USCAR/VRP recyclability and separability ratings (R.R.
and S.R., respectively). (10 points)
c) Identify a number of areas for improvement on the coffee maker. Show how implementing
one of these improvements (pick one) affects the percent recyclability by weight of the coffee
maker? (7 points)
d) What is the main difference between a recyclability rating of 3 vesus 4? (2 points)
e) What is the difference between levels 2 and 3 on the separability scale? (2 points)
f) This approach for measuring the recyclability of a product relies on two rating scales that are
defined by a central authority (the US Vehicle Recycling Partnership). Another approach
would be for each designer to define their own scales. What are the advantages and
5
disadvantages of a unified scale? Do the advantages outweigh the disadvantages or the other
way around? (6 points)
5 – Product Life
(10 points)
Three situations are described below:
A) A t-shirt is designed that will last for 30 years without degrading in any way under normal
conditions.
B) A bridge is designed that lasts for 30 years without degrading in any way under normal
conditions.
C) A laptop computer is designed that lasts for 30 years without degrading in any way under
normal conditions.
In each case, the new product does not harm the environment more than the existing product in
any part of the life cycle. Additionally, the cost of the new products is the same as existing
products. In other words, all else is equal except for the new ability to extend the product lives to
30 years.
a) Is measuring each of these product’s life in terms of years appropriate? How else can you
measure product life? (5 points)
b) In which of the three cases above is designing for 200 years not appropriate? Why is this so?
State any assumptions clearly. (5 points)
6 – Office Seat Dismantling Financial Analysis
(20 points)
An entrepreneur is interested in setting up a dismantling line for office seats. He gets the seats
for free and it takes 3 minutes to manually dismantle the seat and sort the materials. The capital
equipment cost for the facility is $500,000. The operational costs (excl. labor) are estimated to
be about $3,000 per month. Assume that there are 10 workers working 40 hours a week with a
$20 per hour salary (incl. benefits). The material breakdown for the seats is given in Table 6.1.
The prices for the recycled material are given in Table 6.2.
Table 6.1 - Car seat material breakdown
No.
1
2
3
4
5
Material
Steel
PP
Polyester
PUR
ABS
6
Amount (Kg)
10.23
0.14
1.81
3.18
0.03
Table 6.2 - Car seat material prices
No.
1
2
3
4
5
Material
Steel
PP
Polyester
PUR
ABS
Price ($/Kg)
0.12
0.11
0.33
0.55
0.73
a) Given the preceding information and assuming continuous production throughout the year,
how many months will it take the entrepreneur to start making a return on his investment?
(10 points)
b) What are some critical uncertainties which could affect the entrepreneur's business
negatively? (5 points)
c) What is an alternative way to process the seats and what are the economical advantages and
disadvantages? (5 points)
8 – And finally ...
(5 points)
Tell me how you are going to use the material from this class in
a) your future classes at Tech and
b) your professional career.
Have a nice Springbreak!
7
ECO-INDICATOR VALUES
Production of metals (in millipoints per kg)
Indicator
Secondary aluminium
1.8
Aluminium
18
Copper, primary
85
Copper, 60% primary
60
Secondary copper
23
Other non-ferrous metals
50-200
Stainless steel
17
Secondary steel
1.3
Steel
4.1
Sheet steel
4.3
Description
made completely of secondary material
containing average 20% secondary material
primary electrolytic copper from relatively modern American factories
normal proportion secondary and primary copper
100% secondary copper, relatively high score through heavy metal emissions
estimate for zinc, brass, chromium, nickel etc.; lack of data
sheet material, grade 18-8
block material made of 100% scrap
block material with average 20 % scrap
cold-rolled sheet with average 20% scrap
Processing of steel (in millipoints)
Bending steel
Bending stainless steel
Cutting steel
Cutting stainless steel
Pressing and deep-drawing
Rolling (cold)
Spot-welding
Machining
Machining
Indicator
0.0021
0.0029
0.0015
0.0022
0.58
0.46
0.0074
0.42
0.0033
Description
one sheet of 1 mm over width of 1 metre; straight angle
one sheet of 1 mm over width of 1 metre; straight angle
one sheet of 1 mm over width of 1 metre
one sheet of 1 mm over width of 1 metre
per kilo deformed steel, do not include non-deformed parts!
per pass, per m2
per weld of 7 mm diameter, sheet thickness 2 mm
per kilo machined material ! (turning, milling, boring)
per cm3 machined material ! (turning, milling, boring)
Hot-galvanising
17
Electrolytic galvanising
22
per m2, 10 micrometres, double-sided; data fairly unreliable
per m2, 2.5 micrometres, double-sided; data fairly unreliable
Electroplating (chrome)
70
per m2, 1 micrometre thick; double-sided; data fairly unreliable
Processing of aluminium (in millipoints)
Indicator
Blanking and cutting
0.00092
Bending
0.0012
Rolling (cold)
0.28
Description
one sheet of 1 mm over width of 1 metre
one sheet of 1 mm over width of 1 metre
per pass, per m2
Spot-welding
Machining
Machining
0.068
0.12
0.00033
per weld of 7 mm diameter, sheet thickness 2 mm.
per kilo machined material ! (turning, milling, boring)
per cm3 machined material ! (turning, milling, boring)
Extrusion
2.0
per kilogram
8
Production of plastic granulate (in millipoints per kg)
Indicator
Description and explanation of score
ABS
high energy input for production, therefore high emission output
9.3
HDPE
relatively simple production process
2.9
LDPE
score possibly flattered by lack of CFC emission
3.8
Natural rubber
ozone-layer-depleting solvents used during production
15
PA
high energy input for production, therefore high emission output
13
PC
high energy input for production, therefore high emission output
13
PET
high energy input for production, therefore high emission output
7.1
PP
relatively simple production process
3.3
PPE/PS
A commonly used blend, identical to PPO/PS
5.8
PS rigid foam
block of foam with pentane as blowing agent (causes smog)
13
PS high impact (HIPS)
high-impact polystyrene
8.3
PUR
ozone-layer-depleting solvents used during production
14
PVC
calculated as pure PVC, without addition of stabilisers
4.2
Processing of plastics (in millipoints)
Indicator
Injection mould. in general
0.53
Inject. mould. PVC & PC
1.1
RIM, PUR
0.30
Extrusion blowing PE
0.72
Vacuum forming
0.23
Vacuum pressure forming
0.16
Calandering of PVC
0.43
Foil blowing PE
0.030
Description
per kilo material, this figure may also be used as estimate for extrusion
per kilo material, this figure may also be used as estimate for extrusion
per kilo material
per kilo, for bottles and such like
per kilo
per kilo
per kilo
per m2, thin foil (for bags)
Ultrasonic welding
Machining
per metre weld length
per cm3 machined material
0.0025
0.00016
Production of other materials (in millipoints per kg)
Indicator
Description
Glass
57% secondary glass
2.1
Glass wool and glass fibre
for isolation and reinforcement
2.1
Rockwool
score is largely determined by carcinogenic substances
4.3
Ceramics
simple applications, e.g. sanitary fittings etc.
0.47
Cellulose board
this material is particularly used in dashboards
3.4
Paper
chlorine-free bleaching, normal quality
3.3
Recycled paper
unbleached, 100% waste paper
1.5
Wood
wood from Europe, sawn into planks, without preservatives
0.74
Cardboard
corrugated cardboard made of 75% waste paper.
1.4
Production of energy (in millipoints)
Indicator
Electricity high voltage
0.57
Electricity low voltage
0.67
Heat from gas (MJ)
0.063
Heat from oil (MJ)
0.15
Mechanical (diesel, MJ)
0.17
Description
per kWh, for industrial use
per kWh, for consumer use (230V)
per MJ heat
per MJ heat
per MJ mechanical energy from a diesel engine
9
Transport (in millipoints)
Truck (28 ton)
Truck (75m3)
Indicator
0.34
0.13
Train
Container ship
Aircraft
0.043
0.056
10
Fraction
Description
per ton kilometre, 60% loading, European average
per m3 km, 60% loading, European average
per ton kilometre, European average for diesel and electric traction
per ton kilometre, fast ship, with relatively high fuel consumption
per kg !, with continental flights the distance is not relevant
Waste processing and recycling (in millipoints per kg)
Indicator
Notes
Incineration (in modern waste incinerator with heat recovery and flue-gas treatment)
Glass
almost inert material on incineration
0.89
Ceramics
almost inert material on incineration
0.020
Plastics (excluding PVC)
plastics contain heavy metals, but also have a high energy yield
1.8
PVC
PVC contains heavy metals and it has a relatively low energy yield
6.9
Paper and cardboard
heavy metals (ink) are dominant, energy yield is relatively high
0.56
Steel and iron
70% is recovered from slag, particularly larger pieces
1.8
Landfill (in modern landfill site with percolation water treatment and dense base)
Glass
almost inert material on a landfill
0
Ceramics
almost inert material on a landfill
0.027
Plastics (excluding PVC)
0.1 % of all heavy metals released
0.035
PVC
0.1 % of all heavy metals released
0.077
Paper and cardboard
10% of all heavy metals (mainly in ink) released
0.16
Steel and iron
small proportion (ca. 1%) of heavy metals released
0.80
Recycling (note: these values cannot be used for recycling of secondary material)
Glass
less glass has to be manufactured because of glass recycling
-1.5
Ceramics
cannot be sensibly recycled
n.a.
Plastics (PP en PE)
less plastic has to be manufactured because of plastic recycling
-0.46
Engineering plastics
the higher the indicator for production, the higher the "profit"
-0.5 - -5.0
PVC
less PVC has to be manufactured because of PVC recycling
-1.6
Paper and cardboard
less paper has to be manufactured because of paper recycling
-1.8
Steel and iron
less pig iron has to be manufactured because of steel recycling
-2.9
Municipal waste (Processing of waste by average Dutch municipality)
Glass
37% incinerated, 63% landfilled
0.35
Ceramics
37% incinerated, 63% landfilled
0.041
Plastics (excluding PVC)
37% incinerated, 63% landfilled
0.69
PVC
37% incinerated, 63% landfilled
2.6
Paper and cardboard
37% incinerated, 63% landfilled
0.33
Steel and iron
37% incinerated, from which 70% is recovered, 63% landfilled,
1.2
Household waste (Same, but with average separation by consumer (e.g. glass and paper containers))
Glass
61% separated and recycled, rest is municipal waste (see above)
-0.80
Ceramics
almost all processed as municipal waste
0.041
Plastics (excluding PVC)
2% separated and recycled, rest is municipal waste (see above)
0.66
PVC
2% separated and recycled, rest is municipal waste (see above)
2.5
Paper and cardboard
35% separated and recycled, rest is municipal waste (see above)
-0.43
Steel and iron
36% separated and recycled, rest is municipal waste (see above)
-0.28
10