Copyright 2004 Joseph Greene All Rights Reserved1 Environmental Aspects of Plastics Professor Joe Greene CSU, CHICO

Copyright 2004 Joseph Greene All Rights Reserved 1

Environmental Aspects of Plastics

Professor Joe Greene

CSU, CHICO


Topic• Source Reduction• Recycling• Regeneration• Degradation• Landfill• Incineration• Total Product Life Cycle• Future


Source Reduction• Source Reduction

– Reduce the amount of material that is used in any application• Combine parts into larger parts, e.g., 1 liter soda uses 40% less

packaging than (2) 0.5 liters

• Reduce thickness of plastic part, e.g., trash bags had 0.08mm thickness (0.003 in) with LDPE, was reduced to 0.025mm (0.001 in) thickness with stronger and tougher LLDPE

• Reduce thickness by process improvements

• Substitution of plastics for paper have reduced weight of packaging

– 1000 grocery bags from paper weighs 140 lbs and stacks 46 inches

– 1000 grocery bags from plastic weighs 15.6 lbs and stacks 3.5 in

– Recycle in house plastic from sprues and runners back into product.


Recycling Classifications• Recycling

– Collection: plastic listed with recycled number

– Codes for plastics• 1 PET

• 2 HDPE

• 3 Vinyl/PVC

• 4 LDPE

• 5 PP

• 6 PS

• 7 Other

– Handling/Sorting• Maximum economic is obtained when each material is sorted

• Aluminum must be separated from metals since it can’t be readily separated from zinc and brass

• Plastics are sorted mostly by sight. Machines can sort by light absorption


Recycling• Recycling

– Reclamation and Cleaning• Plastic is shredded and cleaned

– End-Uses- Sorted PCR (Post Consumer Recycle)• LDPE for new bags and film• PS in insulation and instrument packaging• PP in automotive parts, e.g., interior door inner panels, head liners, etc.• Mechanical properties drop with use of regrind plastic versus virgin plastic. Max use

of 50% regrind, Typical 20%.

– Definitions• Post consumer material: Plastics is collected from the public and reground back into

pellets for reuse.• Post industrial material: Plastic is collected from industrial companies (like sprues,

gates, runners, scrap parts, or packaging)

– End-Uses- Comingled PCR with several plastics regrind• Other plastics include thermoset materials, elastomers, and composites• Plastic wood with use of comingled PCR that is compression molded and not

injeciton molded usually.


Recycling Methods • Converting collected recycled plastics into post consumer materials or

post industrial materials requires:– Sorting. Plastic is sorted into different types by manual or automatic methods.

• The plastic is put on conveyers and then sorted by color and plastic type.

• The plastic is put in three boxes; PET (#1), HDPE (#2), and all the rest (#3 to #7)

– Chopping. Plastic is shredded after sorting to break the plastic into small particles.

– Washing. Plastic is cleaned to remove debris (metal, food, hair) and contaminants (dirt, paper)

– Extrusion. Plastic is put in an extruder where it is heated and extruded into pellets.

• Screen packs are changed every hour or sooner to remove additional debris.

– Packaging. Plastic is put into containers for packaging and labeled with material type, density, and melt index.


Recycling in Europe• Recycling in Europe

– European Union Packaging and Packaging Waste Directive of 1994– Called for the recovery of 50% to 65% by weight of total packaging

waste with an overall target of 25 to 45% recycling and a specific target of 15% recycling for each packaging material by July 2001. [i]

– The directive resulted in a British law that opted to recover 50% and recycle 25% of packaging by 2001, with a 15% minimum recycling rate for each material.

– A survey from the research study provides an overview of plastic bottle recycling and recommends help from the government to increase the number of collection schemes in more cities and towns in England, Wales, Scotland, and Ireland.

– Help is needed to coordinate transfer stations, material recycling facilities, and bailing facilities that are close to the collection area.

– England, like the US, has an overcapacity of recycling processors and is required to import waste plastic from Europe.

–[i] D. N. Smith, et. al., “A Survey of schemes in the United Kingdom collecting plastic bottles for recycling.”, Resources Conservation and Recycling 25 (1999) 17-34


Recycling in U.S.• Recycling in the U.S.

– Most of the recycled materials are either PET or HDPE (1)• account for approximately 95% of all recycled materials. • The other types of recycled plastics are not used in high enough

volume to impact the recycling rates.

• Recycling in California for 2002 (2)– Recycling rates (pounds recycled divided by pounds sold

• PET (#1) - 36%, HDPE (#2) - 42%, • PVC (#3) - 1%, LDPE (#4) - 0.02%, PP (#5) - 1%, • PS (#6) - 0.04%, and Other (#7) - 0.20

–[1] “2001 National Post-Consumer Plastics Recycling Report”, R. W. Bech, Inc., American Plastics Council, http://www.plasticsresource.com/s_plasticsresource/docs/400/382.pdf

– [2] Darryl Young, “Biannual Report of Beverage Container Sales, Returns, Redemption, and Recycling Rates”, May

10, 2003, http://www.consrv.ca.gov/DOR/Notices/Images/BiAnnual02Long.pdf


Recycling in California• Recycling in California

– California’s Rigid Plastic Packaging Container Act (SB235), in 1991– Requires that every rigid plastic packaging container (RPPC) offered

for sale in the state of California meet one of several criteria designed to reduce the amount of plastic being placed in a landfill.[i] • Having a recycling rate of 25 percent, based on annual reports published

by the California Integrated Waste Management Board (CIWMB), • Having a recycling rate of 55 percent if the primary material is

polyethylene terephthalate (PET), or • Having a recycling rate of 45 percent if it is a brand-specific RPPC. • Other RPPC recycling criteria are the plastic material is made from at

least 25 percent post-consumer resin, is source reduced or "lightweighted" by 10 percent, or is reusable or refillable at least 5 times.

– The recycling rates in California for 2001 are 26.1% for all containers and 31.8% for PET.

[i] http://www.ciwmb.ca.gov/Plastic/RPPC/


Recycling in California• Recycling in California

– California’s Trash Bag Recycled Content Act (SB951), in 1990’s– Requires plastic trash bag manufacturers selling trash bags in

California, to meet either that • The plastic trash bags contain at least 10 percent PCR by weight of the

regulated bags, or • The trash bags meet at least 30 percent of the weight of material used

in all of its plastic products is post-consumer materials.[i] • In 2002, 24 manufacturing companies were in compliance and 4

companies were in non-compliance with the state law. • One-hundred and eighty-three wholesale companies were in

compliance. [ii] – Some of the companies are having difficulty finding high quality

PCR made from LLDPE that can be used in the manufacturing of trash bags and meet the product requirements of trash bags customers.

[i] http://www.ciwmb.ca.gov/BuyRecycled/TrashBags/– [ii]

http://www.ciwmb.ca.gov/BuyRecycled/TrashBags/ComplyList/2002.htm


Recycling in California• Recycling in CA

– The major source of post-consumer plastics is from curbside collection by waste management companies.

– In California in 2000, 76.1% of the homes have access to curbside collection of recycled plastic materials. [i]

– In 2000, plastic waste generation for California was 37.5 million tons, which represents 8.9% of the weight of the landfill and 17% of the volume of the landfill.

– Standards are needed to improve the quality of recycled plastic that is collected.

– If the recovered post-consumer plastics can be separated by resin type, cleaned of all debris, and evaluated for the integrity of the polymer and the depletion of important additives, then, the quality of the PCR will greatly improve.

– The improved quality of PCR can result in substantial increase in the use of the recycled materials with virgin plastics. The quality standards can apply to collection and sorting practices, processing methods, and testing procedures.

–[i] http://www.ciwmb.ca.gov/Plastic/RPPC/


Biodegradable plastics• Biodegradable plastics

– The project will assess the availability of biodegradable materials to be used as trash bags as well as develop standards for testing of the biodegradable plastics.

– The California legislature is considering legislation to require the use biodegradable plastic trash bags.

– Two types of biodegradable plastic materials are available. • Made from organic feed stocks: corn, soy, oils, polylactic acid

(PLA)• Additives that cause the plastics to degrade through composting.

– The biodegradable materials are not very consistent in their ability to degrade or their ability to meet the current requirements for trash bags.

– There is very little work done to date to validate the ability of the biodegradable bags to break down nor the necessary conditions for degradation.


Bio-degradable Plastics• Bio-degradable Plastics

– Naturally-derived polymers• Starch based derived from corn to produce polymers.

– Enzymes are available to degrade them.– Properties are not necessarily available to degrade them.

– Polyesters• Polylactic acid- Produced for many years for the medical industry.• Active research to use polylactic acid in plastics.

– Vinyl polymers• Polyvinyl alcohol (PVOH)- Can be cost effective, but soaks up water.• Ethylene vinyl alcohol (EVOH).• Both requires oxygen to degrade.

– Other water soluble polymers• Polyethylene oxide

– Oxidatively degradable and biodegradable additives• Additives promote degradable, compost-able, and biodegradable plastics (olefins)• EcoSafe product from Plastics Solutions• Preferred method for the Plastic Film and Sheet Companies.• Concern for users of plastic wood that reuses polyethylene


Regeneration• Regeneration

– Process of breaking down polymer molecule into basic chemicals or chemical recycling.

– Easiest to regenerate is condensation polymers, PET and nylon.

– Under high pressure and heat in the presence of a catalyst the molecule unzips and regenerates the monomers.

– Thermoset composites use process of pyrolysys, which is the decomposition of a material using heat in the absence of oxygen.

– Advantage of this process is it is more effective for mixed plastics than PCR

– Disadvantages is the generation of air and water pollution and large amounts of energy required


Disposal• Landfills

– 90% of all solid waste (by weight) in US is sanitary landfill.– Plastics comprise 8 % by weight and 20% by volume.– Paper products comprise 40% by weight and 34% by volume.– Percentage of plastics in landfill has not grown in the last 20

years.

• Incineration– Controlled burning is an option for disposing of a large

percentage of municipal solid waste.– Paper, plastic, and other flammables are separated from solid

waste and pressed into pellets and burned at a separate facility.– Burning generates electricity– Environmental concerns includes creation of toxins (dioxins),

ash problems, and carbon dioxide release for global warming


Incineration• Incineration

– Burning generates electricity

– Energy content of various solid waste Material Energy Value (BTU/pound)

• PET 10,900

• HDPE 18,700

• Rubber 12,800

• Newspaper 8,000

• Wood 7,300

• Yard Waste 2,900

• Fuel oil 20,900

• Coal 9,600


Total Product Life Cycle• Total Product Life Cycle

– What is the total impact of a particular product or product type on the environment over the total life cycle of the product from the creation of the product, its use, and disposal impact.

– Example,

– Polystyrene versus paper cups, Table 23.3


Energy Requirements• Energy Requirements

– Example,

– Paper sack versus Polyethylene sack, Fig 23.3

– Refrigerators and freezers. Plastics are replace of glass and metal • Plastics saved 700 million pounds and require a total of 15.8 trillion BTUs

during production versus 23 trillion BTUs for metal and glass. (Savings of 7.2 trillion)


Energy Requirements• Energy Requirements

– Plastic pipe• More tonnage of plastics hoes into pipe than any other single use.

– Weight of pipe was 2 billion pounds versus metal pipe of 17.5 billion pounds.

– Energy consumption of plastic was 84 trillion BTUs versus 408 trillion BTUs for metal pipe, Savings of 324 trillion BTUs

– Beverage Bottles• PET was introduced in mid 1970s to a market full of glass bottles.

• Energy consumption for plastic is 18.2 trillion BTUs versus 24.2 trillion BTUs for glass. Savings of 16 trillion BTUs, or equivalent to 2.8 millions barrels of crude oil.


Chemical Hazards• Materials

– Resins (See MSDS)• Thermoplastic resins- low toxicity and low health hazard

• Thermoset resins- moderate toxicity and moderate health hazard

– Reinforcements- low toxicity and moderate health hazards (dust)

– Fillers- low toxicity and moderate health hazards (dust)

– Solvents- moderate to high toxicity with moderate to high health hazards

– Catalyst- moderate to high toxicity with moderate to high health hazards

– Plasticizers- low toxicity and moderate health hazards


Material Safety Data Sheet(MSDS)

• Hazardous materials are common in the plastics industry

• MSDS are required to accompany any purchased hazardous industrial raw material.

• Plastics are defined as potentially hazardous because in the course of normal use, plastics may produce dusts, mists, gases, fumes, vapors, or smokes which are dangerous.


Material Safety Data Sheet(MSDS)

• Section I: General Information• Section II: Composition• Section III: Physical Properties• Section IV: Fire and Explosion Hazard Data• Section V: Health Hazard Data• Section VI: Reactivity Data• Section VII: Spill or Leak Procedure• Section VIII: Occupational Protective Measures• Section IX: Special Precautions• Section X: Transportation

Documents

Copyright 2004 Joseph Greene All Rights Reserved1 Environmental Aspects of Plastics Professor Joe Greene CSU, CHICO