ENVIRONMENTAL ISSUESCHAPTER 11

Matakuliah : S0782 - Teknik LingkunganTahun : 2009

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ENVIRONMENTAL ISSUES

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OUTLINE•Problem statement•Global look at the problem•Solid waste problem•Possible solutions to solid waste problem•Green design•A success story

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Facts and Myths

• A world without plastics and composites!

• Unfair bad reputation

• Potential to do better

http://www.epa.gov/epaoswer/non-hw/muncpl/facts.htm

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Environmental loads by manufacturing sector

Carbon Dioxide and Toxic Materials per Value of Shipments

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11.5

22.5

33.5

44.5

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Wei

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CO2 (metric ton/$10,000)

Toxic Mat'ls (lb/$1000)

EPA 2001, DOE 2001

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Waste Definitions• WASTE

• WASTE CLASSIFICATION

• SOLID WASTE:

• Metals• Plastics• Paper• Hybrid Materials• ….

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What are the choices?

• Recycling (Physical and/or Chemical)

• Waste to Energy Incineration

• Land filling

• Degradation

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Recycling Techniques• Primary: Conversion of waste into materials

having similar properties• Secondary: Conversion of waste into materials

having inferior properties• Tertiary: Conversion of waste into chemicals and

fuels• Quaternary: Conversion of waste into energy

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Types of Plastic Recycling• Chemical Recycling

– The depolymerization of certain condensation or addition polymers back to monomers

• Mechanical Recycling– The direct recycling and conversion of plastics from

discarded materials into a reusable form

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Factors Impeding Reclaiming• Collection

• Heterogeneous in Nature• Different Plastics• Different Brands

• Non-plastic Contaminants• Metals• Pigments and Dyes• Label Materials• Adhesives• Additives• Filler/Reinforcements• …

• Low Economic Value

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Chemical Recycling• Chemicals can be used for feedstock use or fuel• Problems with chemical recycling

– Greater accumulation of air and water pollution– Some regenerated monomers are pollutants– By-products can be pollutants– Requires considerable amount of thermal and chemical energy

to break apart and then more to repolymerize

• Currently there are no chemical recycling plants, everything is experimental

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Chemical: Tertiary Recycling• Hydrolysis• Alcoholysis• Hydrogentation• Pyrolysis

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Chemical: Quaternary

Astrom, Manufacturing of Polymer Composites, Chapman &Hall1997

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Mechanical Recycling• Most economical and common type of plastic

recycling in the U.S.• Currently 1,677 companies handle and reclaim

plastics• Steps to mechanical recycling

– Collection– Sorting– Reclamation

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Collection• Commingled or sorted collection

• Curbside or drop-off recycling program

• 63% of nation total has access to recycling program

• Currently the amount of some plastics being collected falls short of the capacity of the recycling facilities

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Material Recovery Facility• Two functions

– Separating materials – Prepare materials for the market

• Material is tipped on to the receiving floor• Pushed by front end loader on to the feeder conveyor• Elevated to presort station• Overhead magnetic separation stage• Density separator• Manually sorted• Stored in bunkers until bailed

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Material Reclaiming Facility• Sorted plastics are converted into pellets or flakes• Shredded• Contaminant removal

– Air classifier– Float/sink tank– Washed– Dried– Granulated– 2nd air classifier

• Made into pellets by extrusion or boxed for market as flakes

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Green Thinking• Reduce waste at source• Increase reuse and recycling• Recover energy• Dispose of unavoidable waste safely

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Design for Waste Minimization• Use less raw material• Use less virgin material• Design for equal lifetime of components in an

assembly• Design for transportation• Design for damage tolerance and repair• Design for afterlife potential

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Design for Recycling• Design for disassembly• Label components• Use few combination of materials• Design the labels appropriately (same material)• Avoid painting and adhesive joining• Minimize number of metal fasteners• Exclude undesirable melt-reactive combinations• Avoid non-Separable Colorants

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Story of PET

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Why PET Recycling?

• 8 % (volume %) of this solid waste is PET and HDPE• Almost 50% of all plastic bottles are made from PET• PET is convenient to recycle• Cost effective

Collection $.07/lb.Reprocessing $.30/lb.

Total Cost of recycled PET (flake) $.37/lb. (pellet)

$.46/lb.

Cost of virgin PET $.62/lb.

Savings of $.25- $.16/lb.

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Recycled PET• May be reused between 25 and 40 times• Intrinsic viscosity decreases by .02-.03 dl/g every time it is

re-extruded• Can be compounded to produce a wider range of

properties, products, and markets• Alloying polycarbonate (PC) with recycled PET can produce

an injection–moldable compound, done by GM for bumpers and body panel material (50-60%PET/ 40-50% PC) and is 25-30% less expensive

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Virgin vs. Recycled PET Uses

Virgin PET Uses Recycled PET Uses

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Fiber Market

• Used to make fiberfill which is put in pillows, sleeping bags, ski-jackets, insulation, shoulder pads, etc….– An IV of .58-.65dl/g is adequate– Requires a very clean recycled PET, – cannot use the green recycled PET

• Used to make geotextiles – stabilizers in railroad beds and paved roads– can use the green PET because they are usually pigmented with

carbon black • Used as continuous filament or yarn in such things as carpet

face yarns, or woven carpet backing• Used to make insulation that is as energy efficient as

fiberglass insulation material• Replacing wood fiber

– longer life and less maintenance

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Strapping Market• PET strapping replaces metal strapping used in

pallet wrapping– made by an extrusion process – requires high IV– Mixed with virgin PET or solid stated to increase IV

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Sheeting Market• Used in blister packaging clamshell packages, cups, food

trays, egg cartons, cassette cases, etc…– Needs a high IV

• Making foamed sheets for insulation– uses the green recycled PET with an additive to raise the

normally low melt viscosity– same insulation properties as foamed polystyrene but with

superior cost/performance qualities

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Some Hope• Each Problem Has at Least One Solution

• Some Solutions are Demonstrated Commercially

• There is a Price to Pay for the Solution

• There Are Some Success Stories