Sample Answers to Exercises and Thought Questions: Chapter 12
EX 12.1
List at least 10 types of environmental impacts over the life cycle of your personal computer or mobile phone. Chart these as in Exhibit 12-6, representing your judgment of the relative impact of each life cycle state.
Below are environmental impacts over the life of my personal computer:
(1) natural resource depletion, (2) land degradation due to mining, (3) emissions and waste generation from mining, (4) Reduced biodiversity due to deforestation, (5) air pollution from factory emissions, (6) water pollution from factory discharge, (7) waste generation during production, (8) air pollution due to transportation emissions, (9) waste generation from packaging, (10) electricity consumed during operation, (11) heat generated during operation requires extra A/C in buildings, (12) maintenance and cleaning materials, (13) metals in landfill could leak toxins to water supply, (14) landfill leads to land degradation, (15) waste generation during recovery process, and (16) incineration generates air pollution and toxic ash.
The largest environmental impact for each life cycle stage is put at the top in bold font.
List at least 10 types of environmental impacts over the life cycle of your personal computer or mobile phone. Chart these as in Exhibit 12-6, representing your judgment of the relative impact of each life cycle state.
Below are environmental impacts over the life of my personal computer:
(1) natural resource depletion, (2) land degradation due to mining, (3) emissions and waste generation from mining, (4) Reduced biodiversity due to deforestation, (5) air pollution from factory emissions, (6) water pollution from factory discharge, (7) waste generation during production, (8) air pollution due to transportation emissions, (9) waste generation from packaging, (10) electricity consumed during operation, (11) heat generated during operation requires extra A/C in buildings, (12) maintenance and cleaning materials, (13) metals in landfill could leak toxins to water supply, (14) landfill leads to land degradation, (15) waste generation during recovery process, and (16) incineration generates air pollution and toxic ash.
The largest environmental impact for each life cycle stage is put at the top in bold font.
Materials have the highest environmental impact because there is a large variety of a material needed to build my personal computer. For example, there are many circuit boards with solid-state microelectronics and cabling. These require a lot of copper and rare metals such as gold. All of these materials require extensive mining and processing. The Recovery is also large because of the large amount of waste that will be slow to degrade, and may leak toxins into the soil or air (ex. large plastic enclosures, and the circuit boards contain beryllium). Finally, the Use is very high because of the amount of electricity needed to operate the computer (~70 – 250Watts). The generation of this electricity causes pollution (ex. coal-fired electricity plants), and the computer converts the electricity to heat, which puts an extra load on air conditioners during the warm months.
EX 12.2
Disassemble a simple product, such as a ballpoint pen. Suggest two ways to reduce its environmental impacts.
I disassembled a pair of scissors (see image below). The environmental impact of these scissors can be reduced by:
(1) Providing a sharpening/cleaning service or device for worn out scissors. This might prevent customers from throwing them away and buying a new pair once they become unusable.
(2) Making sure the handle and blade can be more easily separated for recycling.
(3) Using materials that are recycling-compatible. For example, the handle has a rubber lining and the two different materials might make it more difficult to recycle. Also, the rivet that holds the blades and handles together is a different material than the blade and handle.
(5) Reducing the amount of packaging used to transport and sell the product.
(6) Improve the volumetric packing density by transporting the scissors in bulk packaging.
(7) Labeling the components for recycling.
EX 12.2
Disassemble a simple product, such as a ballpoint pen. Suggest two ways to reduce its environmental impacts.
I disassembled a pair of scissors (see image below). The environmental impact of these scissors can be reduced by:
(1) Providing a sharpening/cleaning service or device for worn out scissors. This might prevent customers from throwing them away and buying a new pair once they become unusable.
(2) Making sure the handle and blade can be more easily separated for recycling.
(3) Using materials that are recycling-compatible. For example, the handle has a rubber lining and the two different materials might make it more difficult to recycle. Also, the rivet that holds the blades and handles together is a different material than the blade and handle.
(5) Reducing the amount of packaging used to transport and sell the product.
(6) Improve the volumetric packing density by transporting the scissors in bulk packaging.
(7) Labeling the components for recycling.
EX 12.3
For the product considered in Exercise 1, compute its environmental impact score using any LCA analysis tool available to you.
Performing an LCA on my personal computer would take a large amount of time. Thus, I performed an LCA on my example from Exercise 2, which was a pair of scissors.
I used SolidWorks' SustainabilityXpress plug-in to calculate the environmental impact of a pair of scissors. I first simplified the problem by modeling the pair of scissors as two plastic handles and two stainless steel blades:
For the product considered in Exercise 1, compute its environmental impact score using any LCA analysis tool available to you.
Performing an LCA on my personal computer would take a large amount of time. Thus, I performed an LCA on my example from Exercise 2, which was a pair of scissors.
I used SolidWorks' SustainabilityXpress plug-in to calculate the environmental impact of a pair of scissors. I first simplified the problem by modeling the pair of scissors as two plastic handles and two stainless steel blades:
I then assumed that the metal was drop forged, and the handles were injection molded with ABS plastic. The rivet was not included in this analysis. The final assumption was that they were manufactured in China, and then shipped for use in the USA.
|
Impact Metric
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Plastic Handle
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Metal Blade
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Total (x2)
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|
Carbon Footprint
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0.17 kg CO2
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0.34 kg CO2
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~1 kg CO2
|
|
Water Eutrophication
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9.15e^-5 kg PO4
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3.26e-4 kg PO4
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~8.4e-4 kg PO4
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|
Air Acidification
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1.95e^-3 kg SO2
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4.01e-3 kg SO2
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~12e-3 kg SO2
|
|
Totally Energy Consumed
|
2.09 MJ
|
3.39 MJ
|
~11 MJ
|
Here are the definitions of the impact metrics:
Carbon Footprint - Carbon-dioxide and other gasses which result from the burning of fossil fuels accumulate in the atmosphere which in turn increases the earth’s average temperature. Carbon footprint acts as a proxy for the larger impact factor referred to as Global Warming Potential (GWP). Global warming is blamed for problems like loss of glaciers, extinction of species, and more extreme weather, among others.
Water Eutrophication - When an over abundance of nutrients are added to a water ecosystem, eutrophication occurs. Nitrogen and phosphorous from waste water and agricultural fertilizers causes an overabundance of algae to bloom, which then depletes the water of oxygen and results in the death of both plant and animal life. This impact is typically measured in either kg phosphate equivalent (PO4) or kg nitrogen (N) equivalent.
Air Acidification - Sulfur dioxide, nitrous oxides other acidic emissions to air cause an increase in the acidity of rainwater, which in turn acidifies lakes and soil. These acids can make the land and water toxic for plants and aquatic life. Acid rain can also slowly dissolve manmade building materials such as concrete. This impact is typically measured in units of either kg sulfur dioxide equivalent (SO2), or moles H+ equivalent.
Total Energy Consumed - A measure of the non-renewable energy sources associated with the part’s lifecycle in units of megajoules(MJ). This impact includes not only the electricity or fuels used during the product’s lifecycle, but also the upstream energy required to obtain and process these fuels, and the embodied energy of materials which would be released if burned. Total Energy Consumed is expressed as the net calorific value of energy demand from non-renewable resources (e.g. petroleum, natural gas, etc.). Efficiencies in energy conversion (e.g. power, heat, steam, etc.) are taken into account.
TQ 12.1
What are some of the ways in which you have become more aware of your own environmental impact in recent years?
I have become more aware of the environmental impact of my food consumption; everything from food production (water, pesticides, fertilizers, herbicides, fuel used in farming and transportation), to packaging (extra transportation costs because decreased packing density, and landfill or recycling energy). I've also become aware of the affects of air travel (ground air pollution, and green house gasses in the upper atmosphere).
TQ 12.2
For the Setu chair, what types of environmental impacts would be in the use stage of its life cycle?
The Setu chair's environmental impacts during the use stage include:
1. Repairs: Any repairs to the chair will require either a technician to travel to the site, or that the chair be transported or even shipped to a maintenance facility. Both will have an environmental impact because of the transportation fuel, and possible packaging required. These impacts can be reduced by having a rugged design that is able to take abuse and have an extended life. Also, the replacement part is additional material, and the broken part should be recyclable.
2. Cleaning: Users might use toxic chemicals to clean the chair. Herman-Miller might consider a tag on the chair that informs the user which environmentally safe chemicals they should use to clean the chair.
3. Degradation: The cloth and plastic components might abrade, and the small particles could be harmful when breathed. Even prolonged skin contact with such components can be harmful.
TQ 12.3
In what ways can DFE help to improve the quality of a product, in terms of its functionality, reliability, durability, and reparability?
Functionality: The constraints of DFE may force designers/engineers to think "out of the box", which could yield new functions to the product. For example, a DFE strategy could try to reduce the impact of product packaging by making the package something that can be reused, for example as a container. The ability to use the packaging for something useful adds functionality.
Reliability: One of the DFE goals is to "extend the useful product life" (Exhibit 12-5). Thus DFE products should be engineered to last longer, which in turn means they must be more reliable. For example, one way to do this is to make sure that each part of the product lasts about the same amount of time, so one doesn't fail prematurely and cause the user to throw it away.
Durability: A guideline for DFE is to avoid materials that require additional coatings (See Appendix, Guideline #18). For example, if materials are chosen that do not require paint/coatings, then chipping will not occur and thus it could be considered more durable.
Reparability: Another goal of DFE is to facilitate product disassembly for recycling. This will also make the product more easily serviceable if part of the product needs repaired. For example, I have an idea for a recyclable pizza box. One way to make it recyclable is to have the bottom of the box be removable - since the greases (which are mostly at the bottom of the box) prevent the box from being recycled. Thus the bottom can be thrown away while the rest is recycled.
TQ 12.4
For each life cycle stage, identify a product or service that has high environmental impacts during the particular life cycle stage. Then, suggest a new or existing product or service that provides the same functionality with lower (or without any) environmental impacts.
Carbon Footprint - Carbon-dioxide and other gasses which result from the burning of fossil fuels accumulate in the atmosphere which in turn increases the earth’s average temperature. Carbon footprint acts as a proxy for the larger impact factor referred to as Global Warming Potential (GWP). Global warming is blamed for problems like loss of glaciers, extinction of species, and more extreme weather, among others.
Water Eutrophication - When an over abundance of nutrients are added to a water ecosystem, eutrophication occurs. Nitrogen and phosphorous from waste water and agricultural fertilizers causes an overabundance of algae to bloom, which then depletes the water of oxygen and results in the death of both plant and animal life. This impact is typically measured in either kg phosphate equivalent (PO4) or kg nitrogen (N) equivalent.
Air Acidification - Sulfur dioxide, nitrous oxides other acidic emissions to air cause an increase in the acidity of rainwater, which in turn acidifies lakes and soil. These acids can make the land and water toxic for plants and aquatic life. Acid rain can also slowly dissolve manmade building materials such as concrete. This impact is typically measured in units of either kg sulfur dioxide equivalent (SO2), or moles H+ equivalent.
Total Energy Consumed - A measure of the non-renewable energy sources associated with the part’s lifecycle in units of megajoules(MJ). This impact includes not only the electricity or fuels used during the product’s lifecycle, but also the upstream energy required to obtain and process these fuels, and the embodied energy of materials which would be released if burned. Total Energy Consumed is expressed as the net calorific value of energy demand from non-renewable resources (e.g. petroleum, natural gas, etc.). Efficiencies in energy conversion (e.g. power, heat, steam, etc.) are taken into account.
TQ 12.1
What are some of the ways in which you have become more aware of your own environmental impact in recent years?
I have become more aware of the environmental impact of my food consumption; everything from food production (water, pesticides, fertilizers, herbicides, fuel used in farming and transportation), to packaging (extra transportation costs because decreased packing density, and landfill or recycling energy). I've also become aware of the affects of air travel (ground air pollution, and green house gasses in the upper atmosphere).
TQ 12.2
For the Setu chair, what types of environmental impacts would be in the use stage of its life cycle?
The Setu chair's environmental impacts during the use stage include:
1. Repairs: Any repairs to the chair will require either a technician to travel to the site, or that the chair be transported or even shipped to a maintenance facility. Both will have an environmental impact because of the transportation fuel, and possible packaging required. These impacts can be reduced by having a rugged design that is able to take abuse and have an extended life. Also, the replacement part is additional material, and the broken part should be recyclable.
2. Cleaning: Users might use toxic chemicals to clean the chair. Herman-Miller might consider a tag on the chair that informs the user which environmentally safe chemicals they should use to clean the chair.
3. Degradation: The cloth and plastic components might abrade, and the small particles could be harmful when breathed. Even prolonged skin contact with such components can be harmful.
TQ 12.3
In what ways can DFE help to improve the quality of a product, in terms of its functionality, reliability, durability, and reparability?
Functionality: The constraints of DFE may force designers/engineers to think "out of the box", which could yield new functions to the product. For example, a DFE strategy could try to reduce the impact of product packaging by making the package something that can be reused, for example as a container. The ability to use the packaging for something useful adds functionality.
Reliability: One of the DFE goals is to "extend the useful product life" (Exhibit 12-5). Thus DFE products should be engineered to last longer, which in turn means they must be more reliable. For example, one way to do this is to make sure that each part of the product lasts about the same amount of time, so one doesn't fail prematurely and cause the user to throw it away.
Durability: A guideline for DFE is to avoid materials that require additional coatings (See Appendix, Guideline #18). For example, if materials are chosen that do not require paint/coatings, then chipping will not occur and thus it could be considered more durable.
Reparability: Another goal of DFE is to facilitate product disassembly for recycling. This will also make the product more easily serviceable if part of the product needs repaired. For example, I have an idea for a recyclable pizza box. One way to make it recyclable is to have the bottom of the box be removable - since the greases (which are mostly at the bottom of the box) prevent the box from being recycled. Thus the bottom can be thrown away while the rest is recycled.
TQ 12.4
For each life cycle stage, identify a product or service that has high environmental impacts during the particular life cycle stage. Then, suggest a new or existing product or service that provides the same functionality with lower (or without any) environmental impacts.
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Life Cycle Stage
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High Environmental Impact
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Lower Environmental Impact
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Impact
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Materials
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Petroleum-based plastic food utensils
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Corn-based plastic food utensils
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Plastic is not renewable
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|
Production
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Typical jeans (pants)
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Levi Water < Fewer Jeans
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Less water usage
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Distribution
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Bottled Water
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Fountain Water
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Air pollution via transportation, material usage/waste
|
|
Use
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Automobile
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Bicycle
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Air pollution
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|
Recovery
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Current pizza boxes
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A newly designed pizza box
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The oil from the pizza contaminates the cardboard, and most current boxes cannot be recycled. I’m proposing a redesign so all or some of the pizza box can be recycled.
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TQ 12.5
How would you explicitly include renewable and nonrenewable energy in the life cycle diagram in Exhibit 12-3? Draw such a diagram and explain it.
How would you explicitly include renewable and nonrenewable energy in the life cycle diagram in Exhibit 12-3? Draw such a diagram and explain it.
Energy is used in all stages of the life cycles, thus the diagram above shows orange and green dashed arrows representing non-renewable and renewable energy, respectively. The most common forms of energy are (1) electricity, and (2) thermal, and both of these can be obtained through non-renewable and renewable sources. Below is a summary of how energy is required in each stage to:
Materials: Extract the materials and process it into stock sizes (e.g. gasoline and electricity to operate mining equipment)
Production: Run the machinery that performs the production processes (e.g. electricity to operate mills and lathes)
Distribution: Distribute the goods (e.g. packing materials/containers, diesel for transport trucks)
Use: Power the product, so it can perform the function for which it was designed. Energy is needed for the use of many, but not all goods (e.g. electric toothbrush requires electricity to operate, cars require gasoline, a bicycle helmet does not).
Recovery: Run the machinery used to recycle the raw materials (e.g. aluminum cans used for soda are recycled into aluminum. This requires a melting process, which uses thermal energy).
TQ 12.6
Explain the relationship between DFE and DFM. Consider, for example, those DFE guidelines related to production in Exhibit 12-8.
The following are similarities between DFE and DFM:
(1) DFM strives to achieve a high quality product while minimizing the manufacturing cost. One way to accomplish this is to reduce waste. This could be accomplished by reducing the amount of material and/or energy used (e.g. production, transportation), which are both DFE guidelines.
(2) Both require cross functional teams.
(3) To be successful, they both must be considered throughout the entire development phase.
(4) Since creativity is required, they both often drive innovation by applying constraints.
(5) The guidelines can be used to compare design options.
(6) The guidelines are a simple alternative to a more detailed analysis.
(7) The entire Bill of Materials is examined in both.
TQ 12.7
Consider the DFE assessment tool used by Herman Miller, which computed the weighted sum scores for material chemistry, use of recycled content, ease of disassembly, and recyclability. What modifications would you propose to create a DFE assessment tool for a different type of product, such as an automobile or a mobile phone?
Since automobiles are both material and energy intensive, I would add a new energy category. The energy required by the new product would be compared with a similar product that already exists. The environmental impact of the energy will depend on the way the energy was generated (e.g. coal electricity plant versus solar or thermal), thus this would also need to be considered. Below is a summary of both the materials and energy factors:
Materials: Extract the materials and process it into stock sizes (e.g. gasoline and electricity to operate mining equipment)
Production: Run the machinery that performs the production processes (e.g. electricity to operate mills and lathes)
Distribution: Distribute the goods (e.g. packing materials/containers, diesel for transport trucks)
Use: Power the product, so it can perform the function for which it was designed. Energy is needed for the use of many, but not all goods (e.g. electric toothbrush requires electricity to operate, cars require gasoline, a bicycle helmet does not).
Recovery: Run the machinery used to recycle the raw materials (e.g. aluminum cans used for soda are recycled into aluminum. This requires a melting process, which uses thermal energy).
TQ 12.6
Explain the relationship between DFE and DFM. Consider, for example, those DFE guidelines related to production in Exhibit 12-8.
The following are similarities between DFE and DFM:
(1) DFM strives to achieve a high quality product while minimizing the manufacturing cost. One way to accomplish this is to reduce waste. This could be accomplished by reducing the amount of material and/or energy used (e.g. production, transportation), which are both DFE guidelines.
(2) Both require cross functional teams.
(3) To be successful, they both must be considered throughout the entire development phase.
(4) Since creativity is required, they both often drive innovation by applying constraints.
(5) The guidelines can be used to compare design options.
(6) The guidelines are a simple alternative to a more detailed analysis.
(7) The entire Bill of Materials is examined in both.
TQ 12.7
Consider the DFE assessment tool used by Herman Miller, which computed the weighted sum scores for material chemistry, use of recycled content, ease of disassembly, and recyclability. What modifications would you propose to create a DFE assessment tool for a different type of product, such as an automobile or a mobile phone?
Since automobiles are both material and energy intensive, I would add a new energy category. The energy required by the new product would be compared with a similar product that already exists. The environmental impact of the energy will depend on the way the energy was generated (e.g. coal electricity plant versus solar or thermal), thus this would also need to be considered. Below is a summary of both the materials and energy factors:
Materials
|
DFE Assessment Factor
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Score
|
Factor Weight
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|
Material chemistry
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30%
|
|
Disassembly
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20%
|
|
Recyclability
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30%
|
|
Recycled content
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20%
|
Energy
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DFE Assessment Factor
|
% Reduction
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Factor Weight
|
|
Energy during production
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30%
|
|
Energy during distribution
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10%
|
|
Energy during usage
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60%
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