Waste & Recycling Facts

Plastics Waste

There are 5 main options to handle plastic waste material:

1. Recycling
2. Energy Recovery
3. Disposal
4. Recycling
5. Composting

Recycling

There are two types of plastics that are recycled:

1. Pre consumer Waste
This is scrap material from the manufacturing process. Over 90% of manufacturing scrap in New Zealand is recycled back into the plastics process. Some NZ manufacturing companies have virtually eliminated their waste stream.

2. Post consumer Waste
This is waste plastic material after it has been used by the final consumer.

Energy Recovery

Recycling can exist at two different levels:-

1. Physical Recycling
This is a physical process where the used plastics are treated with heating and pressure to convert them into new plastic products (Most recycling in New Zealand is physical, because there is insufficient plastic material in New Zealand to justify the capital expense of setting up a chemical recycling plant).

2. Chemical Recycling
This is sometimes called feedstock recycling - and involves chemical processes to release the chemicals locked up inside the plastics. There are 4 main methods used.

1. Pyrolysis . Plastics waste is heated in a vacuum producing a mixture of gaseous and liquid hydrocarbons not unlike petroleum.
2. Hydrogenation. Plastics waste is heated with Hydrogen, This “cracks” the polymers into a liquid hydrocarbon.
3. Gasification. Plastics waste is heated in air producing a mixture of carbon monoxide and hydrogen gases. These are used to produce new raw materials such as methanol, which can also be used as a fuel.
4. Chemolysis. Individual plastics are chemically treated, or depolymerised, and turned back into monomers.

Thermosets and Thermoplastics

All thermoplastics can be softened by heating and reformed into new plastic objects. Thermosets however will not soften on reheating, and therefore can not be reformed into new objects by remoulding. This limits their potential tor recycling.

Stages in Recycling

1. Accumulation by the user. This will involve a change of mindset and behaviour by the consumer.
2. Collection of waste plastics from designated locations. This may be from schools, residents via kerbside collection, or from manufacturing sites.
3. Transportation to a recycling centre. Plastics and other waste products are often bulky, and this can lead to significant transport costs.
4. Sorting. Plastics normally must be sorted. Different resin codes are sorted, often into colour grades as well (although an increasing number of products are being manufactured from mixed plastics).
5. Washing. The recyclate needs to be washed to remove dirt, and other contaminants such as oils or residue of the contents. This is done by chopping the material into flakes and then washing and drying the flakes.
6. Conversion into granules. The flakes may be converted into granules or pellets.
7. The granules can now be used to make new plastic products.

PROBLEMS WITH RECYCLING PLASTICS
There are a number of problems associated with recycling

1. Sorting. In most cases the sorting of plastics is vital. Different resin types cannot be mixed in most recycling processes. Sorting is very time consuming and therefore expensive.
2. Cleaning. Because most plastics have been used for packaging the plastic is often badly contaminated.
3. Cost. Recycling is an expensive process and can result in the recycled plastic resin being more expensive than the virgin resin, largely because of 1 and 2.
4. End uses for the recycled plastic. New Zealand law prevents recycled plastic from coming in contact with food. Recycled plastics are of slightly lower quality than virgin material. Plastics processors have found it challenging to find end uses for recycled plastics, and to have them accepted by the public.

SOME INNOVATIONS IN PLASTICS RECYCLING.

1. The wall of 1.5 litre Coca Cola bottles is made up of three layers of plastic. There is a layer of recycled plastic between two layers of virgin material.
2. Plastic can be recycled into “plastic lumber”. Thus plastic is recycled into seats for park benches, “wood” for fence palings etc.
3. Recycled plastic can be used as a bitumen extender in road construction.
4. Recycled plastic can be added to concrete at a rate of about 15% without reducing the strength of the concrete.
5. Layer boards The technology is being perfected here in New Zealand to blend a mixture of resin types to make a thin layer board for use in palletising goods for transport and storage. A layer board does for plastics what particle board does for wood chips. Layerboards have the potential to replace particle boards because they are not subject to water damage and attack by mould, and are easily sterilised.
6. Recycled plastic chips are being used as an ingredient for potting mixes - especially recycled expanded polystyrene chips.

Landfill

Figures from the Auckland Regional Council indicate that plastics make up 8% of the solid waste stream.

Energy from Plastics

Plastics are very high in energy. Plastic packaging can often be very bulky as well. In some countries plastics are being converted to energy in incinerators to save on space in landfills and to save on using fuel oil. Recent experi­ments indicate that the gases and particles released from the incineration of plastics, in “state of the art” facilities, are not significantly greater than those released when wood burns.

Source: Association of Plastics Manufacturers of Europe

Biodegradable and Photodegradable Plastics

Some plastics can be made to break down in the presence of light or as a result of biological activity.. These plastics will have some specialised uses, but will not solve the waste problem. Products that have decomposed are not available for recycling, or for use as a fuel.

Energy & Resource Conservation

Life Cycle or Cradle to Grave Analysis

When a “cradle to the grave”, or whole life cycle analysis is carried out on plastics products, their use of energy, and other non-renewable resources, compares very favourably with alternative products.
 

Material processing temperatures:

 
Paper vs Expanded Polystyrene Cups

If a polystyrene cup is compared with a cardboard cup from the perspective of resource use in its manufacture, the following figures emerge.

A paper cup uses:

• 15x more chemicals to produce
• 13x more electricity to produce
• 30% more cooling water to produce
• 170x more process water to produce
• 6x more steam to produce
• 40% less petroleum to produce

Plastic Shopping Bags

It is estimated that if a conventional plastic shopping bag was replaced by a paper equivalent, the paper bag would:

• weigh 9 times more
• use 4 times as much energy to produce
• use 3 times as much refuse space
• cost 3 times as much to produce
• and it would take seven truckloads to deliver the number of paper bags that could be delivered in one truck-load of plastic bags.

Food Wastage in Developing Countries

It is estimated that 50% of food in developing countries is wasted. The figure in western countries is around 2-5%. That discrepancy is a manifestation of the differences in packaging used.

Lightweighting

In 1970 a yoghurt pot weighed around 12g. By 1985 the weight of a yoghurt pot had been reduced to around 5g. This is known as lightweighting. It is achieved by innovative plastics engineering. There are many other examples.

In 1970 a detergent bottle weighed 60g. By 1990 the weight had shrunk to around 38g. Plastic supermarket bags are now only 15 microns (micron = 1/1000 of a millimetre) thick, compared to a thickness of 45 microns 15 years ago, without any loss of physical properties.

Plastics Substitution

In almost every sector of the community plastics are being used as substitutes for other materials. In cars the use of 100kg of plastic parts can replace about 200kg to 300kg of conventional materials — thereby reducing fuel consump­tion by 750 litres during the life of the car. The use of plastics in car design is expected to grow steadily at an average rate of 2.5% over the next 15 years.

It is estimated that each international plane saves around $15,000 per year in fuel costs by using plastics beverage bottles rather than glass ones as before.