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Environmentally Conscious Design & Manufacturing. Class 18: Recycle. Prof. S. M. Pandit. Agenda. Definition of recycling Hierarchy of recycling Design for recycling Recycling metals, plastics & forest products Economics. Definition of Recycling.

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Environmentally conscious design manufacturing l.jpg
Environmentally Conscious Design & Manufacturing

Class18: Recycle

Prof. S. M. Pandit


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Agenda

  • Definition of recycling

  • Hierarchy of recycling

  • Design for recycling

  • Recycling metals, plastics & forest products

  • Economics


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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.


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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


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Some Myths - 2

  • Environmental impacts of manufacturing are included in the products

    • Cost = function of:

      • supply & demand

      • governmental policy

      • problems with assigning cost


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Life Cycle of a Product

Source: Bishop, “Pollution Prevention: Fundamentals and Practice”


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Recycling World

  • Categories:

    • Portable high value (computers, auto parts)

    • Metals

    • Plastics

    • Paper

    • Chemicals & glass

    • Food waste

    • Used equipment

    • Building material



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Hierarchy of Recycling Options

Source: Bishop, “Pollution Prevention:

Fundamentals and Practice”


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Steps of Recycling

  • For remanufacture and reuse:

  • Disassembly

  • Cleaning

  • Sorting and inspection

  • Part renewal

  • Re-assembly


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Steps of Recycling (cont.)

  • For material recycling:

  • Separation

  • Discrete subassemblies / joining techniques

  • Sorting

  • Group or classify

  • Reprocessing technology


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Possible Separation for Materials

Source: Bishop, “Pollution Prevention:

Fundamentals and Practice”



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Design for Recycling

Multiple objectives

  • Minimize variety of materials & components

  • Avoid use of toxic materials

  • Ease of disassembly of dissimilar materials


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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


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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


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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


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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.)


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Recycling Metals

  • Mixed metals (plating) - expensive

  • Pure metals - very inexpensive

  • Separation techniques:

    • Manual

    • Automated magnetic separation

    • Chemical separation

      • Pyrometallurgy, hydrometallurgy, electrometallurgy


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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.


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Recycling Rubber

Use as is

(Retreaded tired, fishing banks, etc.)

Mechanical

Recycling

Powdered rubber

(Block, road paving, etc.)

Reclaimed rubber

(Devulcanization by the PAN reclaiming

Feed Stock

Recycling

Thermal decomposition, etc

Energy

Recovery

Recovery of heat energy

Source: Otsuka et al., SAE 2000 world congress


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Recycling Forest Products

  • Paper

    • Fibers get shorter with use & recycling

      • White bond

      • Colored bond

      • newspaper

      • grocery bags

      • toilet paper


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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


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Economics (cont.)

Disassembly cost

Cost

Landfilling Cost

Number of Disassembly Steps


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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


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Homework #6

  • How is the manufacturing economics affected by

  • environmental considerations? (Illustrate your answer by using machining as an example)

  • What steps would you take in a quantitative decision making process? What are the different tools available in this process?

  • Compare and contrast traditional and ECDM guidelines for material selection.


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Homework #6

  • Why is recycling of plastics so important for the ECDM

  • efforts? Give relevant statistics to support your answer.

  • What are the major hurdles in recycling of plastics? How

  • can they be overcome?


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