Matakuliah
Tahun
: S0782 - Teknik Lingkungan
: 2009
ENVIRONMENTAL ISSUES
CHAPTER 11
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
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
CO2 (metric ton/$10,000)
Manufacturing industries
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Transportation
Electronic
Machinery
Fabricated
Metal
Primary Metal
Plastics and
Rubber
Petroleum
and Coal
Toxic Mat'ls (lb/$1000)
Chemicals
Weight/Dollars
Carbon Dioxide and Toxic Materials per Value of Shipments
EPA 2001, DOE 2001
Waste Definitions
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WASTE
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WASTE CLASSIFICATION
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SOLID WASTE:
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Metals
Plastics
Paper
Hybrid Materials
….
What are the choices?
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Recycling (Physical and/or Chemical)
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Waste to Energy Incineration
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Land filling
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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
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Collection
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Heterogeneous in Nature
Different Plastics
Different Brands
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Non-plastic Contaminants
Metals
Pigments and Dyes
Label Materials
Adhesives
Additives
Filler/Reinforcements
…
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Low Economic Value
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Chemical Recycling
• Chemicals can be used for feedstock use or fuel
• Problems with chemical recycling
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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
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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
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Commingled or sorted collection
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Curbside or drop-off recycling program
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63% of nation total has access to recycling program
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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
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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
Material Reclaiming Facility
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Sorted plastics are converted into pellets or flakes
Shredded
Contaminant removal
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Air classifier
Float/sink tank
Washed
Dried
Granulated
2nd air classifier
Made into pellets by extrusion or boxed for market as flakes
Green Thinking
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Reduce waste at source
Increase reuse and recycling
Recover energy
Dispose of unavoidable waste safely
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Design for Waste Minimization
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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
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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?
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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
Reprocessing
Total Cost of recycled PET (flake)
$.07/lb.
$.30/lb.
$.37/lb.
(pellet)
Cost of virgin PET
Savings of $.25- $.16/lb.
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$.46/lb.
$.62/lb.
Recycled PET
• May be reused between 25 and 40 times
• Intrinsic viscosity decreases by .02-.03 dl/g every time it is reextruded
• 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
Recycled PET Uses
Virgin PET Uses
PET Basic Uses
End Uses of Recycled PET
10.00%
5.20%
23.00%
10.00%
16.70%
fiber
10.00%
film
rigid container
6.90%
other
4.00%
71.30%
43.00%
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strapping
sheet
non food bottles
food bottles
Fiber
other
Fiber Market
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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
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Used to make geotextiles
– stabilizers in railroad beds and paved roads
– can use the green PET because they are usually pigmented with carbon
black
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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
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