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Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:1
Environmentally Conscious Design & Manufacturing
Class 18: Recycle
Prof. S. M. Pandit
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:2
Agenda
• Definition of recycling• Hierarchy of recycling• Design for recycling• Recycling metals, plastics & forest products• Economics
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:3
Definition of Recycling
American Automobile Manufacturers Association’s definition
A series of activities, including collection, separation, and processing, by which products or other materials are recovered from or otherwise diverted from the solid waste stream for use in the form of raw materials in the manufacture of new products.
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:4
Some Myths - 1
• Recycling should pay for itself- Bias in data collected, and the inability to
recognize large scale impact has led to reports of “expensive recycling”
- $200 of energy is saved per ton of material recycled
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:5
Some Myths - 2
• Environmental impacts of manufacturing are included in the products- Cost = function of:
» supply & demand» governmental policy» problems with assigning cost
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:6
Source: Bishop, “Pollution Prevention: Fundamentals and Practice”
Life Cycle of a Product
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:7
Recycling World
• Categories:- Portable high value (computers, auto parts)- Metals- Plastics- Paper- Chemicals & glass- Food waste- Used equipment- Building material
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:8
Typical Value for Vehicles
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:9
Hierarchy of Recycling Options
Source: Bishop, “Pollution Prevention: Fundamentals and Practice”
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:10
Steps of Recycling
For remanufacture and reuse:
• Disassembly• Cleaning• Sorting and inspection• Part renewal• Re-assembly
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:11
For material recycling:
• SeparationDiscrete subassemblies /
joining techniques
• SortingGroup or classify
• Reprocessing technology
Steps of Recycling (cont.)
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:12
Possible Separation for Materials
Source: Bishop, “Pollution Prevention: Fundamentals and Practice”
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:13
Example: Polymer Recycling
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:14
Design for Recycling
Multiple objectives
• Minimize variety of materials & components
• Avoid use of toxic materials • Ease of disassembly of dissimilar
materials
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:15
Disassembly
• Design for Disassembly (DFD)
• Ease of Disassembly
- Preferred design: snap-fit, pop-in, pop-out, bolted
or screwed components
- Difficult design: welded, adhesive, threaded
connections
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:16
Disassembly (cont.)
• Simplified Design
- Reduce the number and types of parts
- Reduce product complexity
• Modularity Design
• Material Selection
- Facilitate identification of materials (e.g. Marking plastics)
- Use fewer types of materials
- Use similar or compatible materials
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:17
Disassembly (cont.)• Non-Destructive Disassembly (NDD)
- Minimize the destruction of the product
- Maximize the potential of material resource and
sub-component reuse
• Destructive Disassembly (DD)
- Destroy one or more components so that the others
can be disassembled
- Save more expensive components- Recycle materials
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:18
Disassembly (cont.)
• Disassembly Strategy
- Analyze feasibility of part reuse and materials recovery
- Generate optimal disassembly sequence
- Disassembly optimization (Lower disassembly cost,
higher rate of component reuse, higher rate of material
recycling, etc.)
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:19
Recycling Metals
• Mixed metals (plating) - expensive• Pure metals - very inexpensive• Separation techniques:
- Manual- Automated magnetic separation- Chemical separation
» Pyrometallurgy, hydrometallurgy, electrometallurgy
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:20
Recycling Plastics
• Thermoplastics - easy- Polyethylene terepthalate, polyvinyl chloride,
low density polyethylene, polypropylene
• Thermoset plastics- Phenolics, polyesters, epoxides: -
crosslinking, need pyrolysis / hydrolysis to reduce mol. Wt.
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:21
Recycling Rubber
Mechanical Recycling
Feed StockRecycling
Energy Recovery
Use as is(Retreaded tired, fishing banks, etc.)
Powdered rubber(Block, road paving, etc.)
Reclaimed rubber(Devulcanization by the PAN reclaiming
Thermal decomposition, etc
Recovery of heat energy
Source: Otsuka et al., SAE 2000 world congress
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:22
Recycling Forest Products
• Paper- Fibers get shorter with use & recycling
» White bond» Colored bond» newspaper» grocery bags» toilet paper
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:23
Economics
• Recycling must be profitable
• Revenue from recycling:- High value, reusable subassembly and parts - Recycled materials and energy
• Cost incurred by recycling:- Investments in recycling equipment- Labor cost- Other cost such as transportation, equipment
operating
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:24
Economics (cont.)
Number of Disassembly Steps
Co
st
Landfilling Cost
Disassembly cost
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:25
References
• Graedel & Allenby, Industrial Ecology, 1995• http://minerals.usgs.gov/minerals/pubs/commodity/recycle/
index.html• http://doemetalsrecycle.ornl.gov/• http://www.edf.org/pubs/reports/armythfin.html• http://www.recycle.net/recycle/• http://mime1.marc.gatech.edu/Courseware/autorecycling/
MatRecyc.html• http://srl.marc.gatech.edu/education/Recycle/EnergRec.
html
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 17, 2000 Slide:26
Homework #6
1 How is the manufacturing economics affected by environmental considerations? (Illustrate your answer by using machining as an example)
2 What steps would you take in a quantitative decision making process? What are the different tools available in this process?
3 Compare and contrast traditional and ECDM guidelines for material selection.