Plastic

Per capita, consumption of plastics in Australia is estimated to be around 55kg per person annually, contributing around 8% to the weight of domestic refuse. With an estimated 30000 tonnes of plastic being discarded in Western Australia annually (60% of consumption is for long term use items), only a small percentage of production is being recycled, (PIA Inc, 1989), in fact less than 2000 tonnes Australia wide. The energy that goes into producing plastics varies greatly, depending on the processes involved and the type of plastic being produced. To allow for this variation, five types of thermoplastics have been analysed, their selection being based on those plastics found most frequently in domestic refuse.

Polyethylene is usually classified as either high density or low density, items made from low density polyethylene (LDPE) include plastic shopping, storage, and 'boutique' bags, food wrapping and horticultural and gardening plastic. High density polyethylene (HDPE) has widespread use as food and beverage packaging, such as the one and two litre Masters, Brownes, Peters, and Harvey Fresh milk containers, all produced locally by Masters Dairy in Bentley. These containers are suitable for recycling, with the potential for the material to be used as the base resin from which new containers can be made. Over 1000 tonnes of HDPE milk containers will be produced and used in Western Australia this year. Over 800 tonnes found their way into Western Australian landfill sites last year.

Composition of domestic refuse by plastic type

high density polyethylene (HDPE)

28%

low density polyethylene (LDPE)

30%

polyethylene terephthalate (PET)

8%

polypropylene( PP)

16%

polystyrene (PS)

6%

polyvinyl chloride (PVC)

8%

other

4%

Polyethylene terephthalate, or PET, is a light-weight and shatter-proof plastic used for soft drink containers. PET bottles contribute 0.3% by weight to domestic refuse (BRRU, 1989), equivalent to 20 million, two litre bottles, annually in Western Australia alone. The manufacturer of these PET

containers puts the annual Australian import and conversion of PET resin at 20000 tonnes. The current PET reprocessing capacity of existing plants is 500 tonne. An additional 1000 tonnes is being stockpiled for use in the proposed Wodonga plant. Consequently 18 500 tonnes of PET soft drink containers, Australia wide, will find their way into landfill this year. During May this year 1.2 tonnes of PET containers were returned to ACI Plastics Packaging (Bentiey, Western Australia) for reprocessing.

The producers of polyethylene products advocate the ease with which LDPE and HDPE, and PET can be recycled, but the number of places within Western Australia and, Australia, currently recycling these post consumer plastics is severely limited. Prototype PET recycling plants have been established by ACI Petalite in Blacktown, and a new plant is due to be built in Wodonga (Victoria) later this year, and by Smorgon Consolidated Industries in Melbourne. Polypropylene products, such as ice cream, cream cheese and yogurt containers, are being reprocessed and recycled into flower pots locally by Smith and Nephew Plastics (Bayswater).

Plastic manufacturers and recyclers have conveyed the importance of waste plastics being separated according to the type of resin they are made from (that is, HDPE, LDPE, PET, PP, PS, PVC, and the like), and cleaned of all debris, such as labels, tags, dirt and other contaminants, before they will recycle the plastic. Labels on plastic cause problems for people wanting to recycle because many are impossible to remove without the use of a strong solvent. The further separation of plastics according to resin type is again difficult for the simple reason that many plastic products are not easily identifiable as one resin or another, and parts of the container may also be of different resins.

To overcome these problems, it is necessary for plastic manufacturers to assist consumers and collectors by initiating a very obvious coding system for all plastics in use so that they can be separated accordingly. Secondly, where labels are placed on plastic, they should be readily removable or of the same plastic so they can be recycled in the same process as the plastic. The Plastics Packaging Division within the Plastics Institute of Australia Incorporated, have adopted a voluntary coding system for plastic containers based on the system being adopted in the United States of America (mandatory coding by 1991). The code is beginning to appear on the base of some containers and shopping bags available in Western Australia. An official launch of the coding system, by the PI A, will take place during 1990.

With around 30000 tonnes of plastic being landfiiled annually in Western Australia, approximately 4 petajoules of energy are being wasted. This is sufficient energy to supply the annual requirement of 290000 Perth homes. The recent introduction of photodegradable and biodegradable plastics is ineffective in reducing the amount of plastics that are being landfiiled, and does not lead to a reduction in the total energy expenditure of plastic production.

Members of the plastics industry have alluded to potential problems within future plastic recycling schemes where degradable plastics are present, claiming that they may reduce the strength and quality of the recycled product. This has been counteracted by the manufacturers of degradable plastics. Evidence in support of either allegation is yet to be forthcoming.

The major stages of energy expenditure in the manufacturing of plastics have been analysed as shown below, for high density polyethylene, low density polyethylene, polyethylene terephthalate, polypropylene, polystyrene and polyvinyl chloride.

Plastic from raw materials

Recycling of plastic

1

Mining and extraction of raw materials

1

Recycling material collection door to

door

2

Transport of raw material to refinery

2

Transport to recycling centre

3

Conversion; polymerisation;

3

Sorting, washing, reprocessing,

resin manufacture; granulation

granulation, drying of plastic

4

Transport of granules to plastic

4

Transport to plastic products

products manufacturer

manufacturer

5

Manufacture of plastic product

5

Manufacture of plastic product

6

Energy saving by recycling plastic

High density

polyethylene production

I Energy saving 0 Raw materials Q Recycled ma tenais

Figure 6: Energy required to produce one tonne of high density polyethylene from materials and from recycled high density polyethylene

Figure 6: Energy required to produce one tonne of high density polyethylene from materials and from recycled high density polyethylene

Low density polyethylene production

Low density polyethylene production

High Density Polyethylene Transformation

Energy saving TOTAL

Figure 7: Energy required to produce one tonne of low density polyethylene from materials and from recycled low density polyethylene

Energy saving TOTAL

Figure 7: Energy required to produce one tonne of low density polyethylene from materials and from recycled low density polyethylene

Polyethylene terephthlate production

■ Energy saving □ Raw materials D Recycled materials

Polyethylene terephthlate production

■ Energy saving □ Raw materials D Recycled materials

$ Energy wring TOTAL

Figure 8: Energy required to produce one tonne of polyethylene terephthaiate from raw materials and from recycled polyethylene terephthaiate soft drink bottles

Polypropylene production

Polypropylene production

Energy caving TOTAL

Figure 9: Energy required to produce one tonne of polypropylene from raw materials and from recycled polypropylene

Energy caving TOTAL

Figure 9: Energy required to produce one tonne of polypropylene from raw materials and from recycled polypropylene

Polystyrene production

  • Energy saving □ Raw materials 0 Recycled materials
  • Energy saving □ Raw materials 0 Recycled materials

S Energy saving TOTAL

Figure 10: Energy required to produce one tonne of polystyrene from raw materials and from recycled polystyrene

S Energy saving TOTAL

Figure 10: Energy required to produce one tonne of polystyrene from raw materials and from recycled polystyrene

Polyvinylchloride production

Polyvinylchloride production

Energy saving TOTAL

Figure 11: Energy required to produce one tonne of polyvinyl chloride from raw materials and from recycled Polyvinylchloride

Energy saving TOTAL

Figure 11: Energy required to produce one tonne of polyvinyl chloride from raw materials and from recycled Polyvinylchloride

An energy saving in the range of 40% to 60% is achieved in the recycling of plastic, depending primarily on the type of plastic being recycled.

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