Development of a Regional Waste Recovery / Processing Sector

Acknowledgements

Executive summary

1. Introduction

2. Total waste stream and quantities of plastic, glass and tyres

3. Projected waste quantities

4. Reprocessing technologies for tyres

5. Reprocessing technologies for plastic

6. Reprocessing technology for glass

7. Conclusion

References

Appendix A: Template for Assessing the Regional Suitability of Waste Reprocessing Technologies for Tyres, Plastic and Glass

Appendix B: Major European PET and HDPE Reprocessors

5. Reprocessing technologies for plastic

5.1 Introduction

Worldwide production and consumption of plastics is expected to increase by 4% annually with polyethylene (PE), polypropylene (PP) and polyvinal chloride (PVC) production expected to increase by 3.9%, 5.5% and 3.7% respectively. More specifically it is predicted that the consumption of plastic will increase in the U.S and Western Europe by an annual rate of 3.3%, while plastic consumption in Asia is projected to increase by an annual rate of 5.2% (IWMB, 1996).

Plastic has become a widely used commodity because of its inherent characteristics of being light, durable, strong and versatile. As a result plastic manufactured products are energy efficient when compared to alternative materials such as glass and paper. However, these same characteristics mean that plastic is a very complex and difficult material to recycle and reuse, particularly in the New Zealand context where a low population density, large geographical area and isolation make transportation and processing of the various plastic polymers intrinsically difficult.

It is widely recognised that plastic recycling can make a valuable contribution to sustainable waste management and as plastic is increasingly being used as the material of choice in the manufacturing and packaging industry it is necessary that collection and reprocessing infrastructure is further developed.

There are 400 plastic product manufacturers and raw material suppliers in New Zealand. These collectively employ 6,800 employees. The New Zealand plastics sector produces packaging, construction, agriculture, and household products for domestic and international markets. New Zealand manufacturers produced 237,446 tonnes of plastic product in 2001 with 29,665 tonnes recycled. If current trends continue plastic production is expected to climb to 300,000 tonnes by 2020. Although the quantities exported and imported in the form of packaging can be ascertained, the volume exported and imported as packaging for other products can only be estimated. The various end uses of plastic produced in 2001 are shown below along with quantity of each polymer consumed and recycled (Cox, 2002)

It is estimated that over 189,000 tonnes of plastic is landfilled annually in New Zealand. The plastic packaging recycling rate for New Zealand is 18%, which is comparable with most European countries that are estimated to have a recovery rate of between 7% and 22%, with the exception of Germany, which has a packaging recovery rate of 52% due to a mandatory take back scheme. An improvement in the 18% achieved in New Zealand will be needed if the 50% of Councils across the country committed to Zero Waste targets are to achieve progress towards this objective. In these terms a significant opportunity exists to recover a greater quantity of plastic through improved collection and reprocessing (Plastics New Zealand, 2002 & RECOUP, 2003).

In the Wellington region it is estimated that 1,440 tonnes of plastic are diverted from landfill per annum through recycling at kerbside collections systems and drop-off sites, while a further 25,348 tonnes of plastic are landfilled. However, due to commercial sensitivity no information is available with regards to the breakdown of the various plastic polymers collected and reprocessed across the region.

5.2 Plastic Recyclate Diversion

Managing waste plastic falls into four generic categories: collection, sorting, processing and end use.

Collection

Plastic is considered a complex material to recycle when compared to other commodities such as aluminium or glass for example. Many councils across New Zealand are struggling to decide which plastic polymers to collect and as a result it is often the case that various councils across a region will collect a range of different materials. The table below shows that while all councils across the region collect PET and HDPE, a variation does exits with regards to the remaining plastic polymers collected for reprocessing. A more coordinated and consistent approach across the region would prove beneficial in that increased volumes of compatible resins would be collected which would help achieve economies of scale for the reprocessing sector.

Table 5.1: Plastics recovered for recycling by councils in the Wellington region

Council	Bread & Carrier Bags	PET (1)	HDPE (2)	PVC (3)	LDPE (4)	PP (5)
Wellington City
Lower Hutt City
Upper Hutt
Porirua
Kapati Coast District
Masterton District
Carterton District
South Wairarapa

Public participation is the key to any household recycling initiative as it determines the quantity of material that can potentially be recovered. The average participation rate of kerbside collection systems in the UK is reported to be 62% with 100% participation perceived to be unobtainable without mandatory provisions introduced. Other factors that influence the quantity of material recovered through plastic bottle collection schemes include:

• Collection container used (both bring and kerbside collection systems)
• Bring scheme site density
• Collection scheme logistics
• Participation rate
• Scheme promotion
• Local Socio economic status
• The quantity of plastic present in the waste stream

Sorting

Prior to reprocessing the various plastic polymers automatic or manual sorting is to separate the various plastic polymers or alternatively mixed plastic can be reprocessed to make lower grade products.

Manual and automatic sorting systems are available for the various plastic polymers however, in New Zealand it is primarily achieved through manual methods using the Plastic Identification Code. This may often prove to be labour intensive, costly and time consuming with the results often poor. A number of automatic techniques have been developed for identification and sorting of plastic polymers based on the different chemical, optical, electrical or physical properties of the various materials. They include density-based sorting, optical sorting, spectroscopic-based sorting, X-ray fluorescence for sorting PVC and sorting by selective dissolution (Scheirs, 1998).

Once the polymers have been sorted into their various types if they are to be used as feedstock for anything other than low-grade material it is necessary for them to be put through a washline. This is an expensive process and often forms the limiting factor to increasing the reprocessing capacity for the various plastics in New Zealand.

Reprocessing

The recycling of plastic is generally achieved using mechanical processes such as shredding, grinding and pressing plastic into granules that are subsequently used, often with virgin resin, to produce the same, similar or different products to the original. This technique is used in both primary and secondary recycling. Primary recycling refers to the reprocessing of waste plastic generated from the manufacturing processes such as resin production or moulding. This pre-consumer material is then mixed with virgin material and reused in the manufacturing process. The recycling rate for this type of plastic is generally high with a 94% rate in Japan, 95% in the UK and an estimated 90% in New Zealand. Secondary recycling refers to post consumer plastic collected often from the residential waste stream or from the manufacturing process where one or more polymers are present. Post consumer plastics are often contaminated making sorting a complex and expensive process and Scheirs (1998) determined that 1% of incompatible polymer can be sufficient to degrade the properties of an entire batch of recyclate (Liu, 2000).

End Uses / Markets

The economic viability and development of end use markets for plastic varies considerably and the number of applications for end use markets is extensive, with a wide range of products already being produced. However, it remains that the use of recycled plastic in manufacturing needs to be promoted to educate and encourage the public to buy products that are made from the recycled material that they themselves contributed to.

While collection, sorting, reprocessing and end use markets are all intrinsically linked this investigation will primarily focus on the development of existing, new and emerging technologies that may be used to develop a reprocessing sector for the designated waste stream.

5.3 The Various Plastic Polymers

Plastic recycling is more complex due to the wide range of plastic polymers that exist. A Plastic Identification Code has been introduced in many countries to assist the sorting and processing of the various plastic types. The New Zealand Identification Code is included below, along with a brief summary of various factors affecting the recovery and recycling of these materials:

HDPE (High Density Polyethelene (1)) and PET (Polyethylene Terephthalate (2)) should form the fundamental component of a kerbside collection system as sorting is limited and markets are well established. The sorting of HDPE and PET is limited to milk bottles or uncoloured HDPE and the coloured grade HDPE that is often referred to as 'janitorial' grade and clear and coloured PET. Plastic New Zealand estimate that only 27-30% of the bottles and containers manufactured from these materials are being collected. Continued promotion and education of HDPE and PET bottles and containers is vital if improvements in the recovery rate are to be achieved. Promotion of soft drink and milk bottle kerbside collections has been very positive, but other containers have not been heavily publicised. These include cleaning containers, shampoo bottles, salad domes, and strawberry punnets for example. Most HDPE is reused within New Zealand, however all PET is exported to China, Asia or Australia as currently there is insufficient volumes generated to justify installing a washline as part of the reprocessing procedure.

A number of Councils are still promoting or considering introducing PVC (Poly Vinyl Chloride (3)) kerbside collection. There are only 824 tonnes of PVC packaging manufactured in New Zealand each year (compare this with the 16,325 tonnes of PET). Not only are the volumes of PVC available insignificant, but PVC acts as a contaminant in the PET and HDPE recycling streams. Industry is actively investigating avenues for recycling PVC products other than packaging, there is already one successful business recycling cable material and a pipe company is currently trialing PVC pipe recycling.

LDPE (Low Density Polyethylene (4)) is commonly used for film, with 40,197 tonnes of New Zealand produced film being used for packaging each year. There are well-established markets for commercial shrink and shroud wrap with independent commercial collectors. New Zealand industry is undertaking to label all printed films with the plastics identification code to allow ease of identification - however this is done on a voluntary basis and is not mandatory. Food and waste contamination is a major barrier to the recycling of household film waste given the lack of washline facilities in New Zealand. Any Council undertaking to collect films should seek clear guidance on market specifications for sorting and identification.

PP (Polypropylene (5)) is a rapidly growing high value material with specifications that are constantly improving. 9,821 tonnes of PP packaging were produced for New Zealand usage in 2001. This is predicted as the next viable material for kerbside collection. The main difficulty with promoting this is the vast array of product types in PP. These include fast food containers, bottles, tubs and 1kg yoghurt containers. The success of PP will be heavily dependent on the promotion of the (5) code with the public by Councils, the increased use of PP by manufacturers, ease of visual recognition by sorters on recycling lines and establishing markets for reuse.

PS (Polystyrene (6)) is used mainly in foamed or rigid food contact packaging. 6,185 tonnes of New Zealand rigid PS packaging was produced in 2001. Again economics and the lack of a washline to enable the reuse of this material is a barrier to creation of any post consumer recycling. EPS (Expanded Plystyrene (6)) packaging while high in volume, being 98% air, used only 794 tonnes of raw material in 2001. Again low levels of material provide an economic barrier to establishing recycling. The level of imported EPS packaging is unknown, further research to investigate material volumes may help support the business case for this. The Expanded Polystyrene Sector Group is actively investigating technology to provide recycling solutions (Cox, 2002).

One of the main issues surrounding the reprocessing of plastic is contamination. This relates to the presence of non-plastic materials such as metal or glass or due to the mixing of various plastic polymers such as PET, HDPE and PVC. One of the primary concerns relating to the latter is an increase in the manufacture of drinks bottles made from PET with a PVC sleeve added for marketing purposes. Designers have adopted the use of PVC as it is cheap compared to alternatives, easy to print on and readily shrinks the marketing graphics around a complex shape such as a bottle. Most of these milk flavoured drinks are imported from Australia where they are also facing the same problem, however increasingly more mainstream local beverages are also being manufactured. Producers, manufacturers, retailers and recyclers need, perhaps, to work more closely on resolving such issues.

The most common method for separating individual plastic polymers during PET recycling is by flotation in a water batch after the material has been granulated. If the plastic, labels and other contaminants have a specific gravity of < 1 (the specific gravity of water) then they will float. PET has a relatively high specific gravity (1.38) and therefore sinks. Unfortunately both PET and PVC (1.35) have very similar specific gravities and thus cannot be sorted by this method. This means that packaging that uses a mix of PET and PVC cannot be easily sorted and therefore economically recycled even though both materials are able to carry the appropriate recycling symbols.

An additional plastic contamination issue relates to metallised inks and labels that fragment during the recycling process and sink along with the PET granules during the flotation screening. This creates fine metallic particles that create black specks that cannot be removed from the PET resin. At this stage there is no economic process in place to separate the PVC labels or metallised inks from the PET or HDPE products (Plastics New Zealand¹, 2002).

In an attempt to address such contamination issues the French have recently introduced a system where the recyclability of packaging is assessed by a central certification body (COTREP). Packaging that is accredited with a low score may be shunned by major retailers who contribute to costs associated with the recycling of packaging throughout the county.

5.4 Plastic Reprocessing Technologies

5.4.1 Mechanical Reprocessing

Secondary processing can be classified into two groups: homogenous or mixed (commingled), depending on the quality of the feedstock and the intended product or end-use. Homogenous resin recycling refers to the process used for individual plastic polymers and therefore, once mixed the plastics have to been sorted by resin type and cleaned in a washline before the material can be reprocessed. Once this has been completed the material is transformed into a flake or pallatised form by applying heat or alternatively chipped so that it is ready to be reused in the manufacturing process. Homogenous resins usually compete with or are blended with virgin resin and are used as raw materials to make relatively high value products usually through injection moulding and extrusion.

When individual plastic resins are not sufficiently valuable to make separation economically viable then commingled plastic may also be reprocessed using similar techniques. The material does not usually compete with virgin material but with other materials such as timber, concrete ceramics and metals. The mixed resins recycling process has a different thermal stability and processing behaviour when compared to the homogenous process as mixed resins need to be heated above the melting point for the dominant resin in the blend and then extruded or moulded into the desired product shape.

Mechanical technologies are also being developed to separate plastic from non-plastic materials such as cardboard cartons. For example, the UK's first commercial plant has opened in Fife in Scotland, which is capable of processing 15,000 tonnes of cartons per year which is 20% of the UK arisings. The Smith Anderson Group mill in Leslie recycles the paper and cardboard fibre and processes a range of products including small cardboard boxes, cartons and envelopes that all contain a proportion of plastic. The joint venture between the mill and Liquid Food Carton Manufacturers Assocaition has spent $900,000 on a large trommel screen which us used to separate the plastic film and aluminium foil from the paper fibres. Initially the plant will be used for converting waste generated from packers and fillers but the company are currently negotiating with local authorities to encourage cartons to be collected in kerbside collection schemes. Cartons could be collected across the UK as Smith Anderson has an existing regional network of depots. Germany, Belgium, Luxemboug, Sweden and Norway all had carton recycling rates above 40% in 2001 (ENDS, Issue No. 337, 2003).

5.4.2 Multilayer Processing

High quality mechanically recycled food grade polymer, derived from sources such as limited refill bottles and bottles recovered through deposit or kerbside collection schemes, may be sandwiched between layers of virgin polymer through a process called co-extrusion. Acceptance of multilayer bottles for food contact applications was initially dependent upon the demonstration of the functional barrier preventing the migration of contamination that may be present in the recyclate to the foodstuff. Multilayer bottles generally incorporate 50-60% of recycled PET and are now well established for food contact applications in several markets including New Zealand.

5.4.3 Superclean (physical) Recycling

Several organisations have developed processes using mechanical and non-mechanical procedures to recycle high quality post consumer material to produce polymer suitable for use in mono-layer applications i.e. use in direct contact with food. Superclean processing involves the removal of volatile contaminants with maintenance / raising of intrinsic viscosity (IV) to bottle grade (0.75-0.82 dl g-1). The processes generally involve combinations of standard mechanical recycling processes with non-mechanical procedures such as high temperature washing, high temperature and pressure treatments, use of pressure / catalysts and filtration, to remove polymer entrained contaminants and raise IV.

5.4.4 Chemical Reprocessing

Chemical recycling involves de-polymerising long chain plastic materials into their original monomer molecules and then re-polymerising these monomer molecules into virgin resin, or braking plastics and monomers down into their constituent molecules for reuse in refineries or petro-chemical production. This is often referred to as feedstock recycling and is primarily achieved through thermolysis and chemolysis.

1. Thermolysis

Thermolysis involves the application of high temperatures and pressures to break down the organic component of the plastic into its original monomers or constituent chemicals that are high value petrochemical feedstocks that can be used as raw materials in the production of new petrochemicals and plastics. The main forms of feedstock recycling by thermolysis include pyrolysis, hydrogenation and gasification.

• Pyrolysis (also called thermal cracking) is the decomposition of plastic waste using temperatures of up to 800ºC in the absence of air, or in an atmosphere deficient of oxygen, to produce gaseous or liquid hydrocarbons. The process generates products that need further processing in refineries in order to separate or purify the constituent molecules. Pyrolysis technologies have been developed by BASF in Germany, Fuji Tech in Japan and Conrad in Canada, all of which involve the processing of plastic waste in kilns, while BP Chemicals have developed a fuidised bed cracking process that produces a more uniform product with less unwanted side reactions.
• Hydrogenation (or hydrocracking) involves the decomposition of plastic in an atmosphere of hydrogen gas under high temperatures and pressures to produce hydrocarbon oils. This process requires only very minor pre-treatment of municipal plastic waste and can obtain high value products. It has been regarded as a better feedstock recycling procedure than either pyrolysis or gasification. The German VEBA Oel hydrogenation process is the longest running operation in Europe and converts 120,000 tonnes of plastic waste per year into quality synthetic oil.
• Gasification involves the decomposition of plastic in the presence of a controlled amount of oxygen at higher temperatures than pyrolysis (1300ºC) which is converted into a gas that can be used as a substitute for natural gas.

Two thermolysis systems have been operating successfully in Japan and the Melbourne based environmental technology company Ozmotech is planning to expand with interest already being demonstrated in South America, Europe, and the US, with the New Zealand agent for Ozmotech Orvco, based in Christchurch. The process is successfully and economically converting waste plastic into clean burning low sulphur (5ppm) distillate diesel fuel, which is then used on site to drive two 288 kW/h generators which provides the electricity for the company therefore eliminating their power bill and the need for alternative waste disposal. The feedstock is waste plastic generated from the company's own manufacturing process but virtually all plastics can be processed using this system. This included HDPE, LDPE, film and wraps along with other plastic bottles and containers. The thermolysis system can process up to 8 tonnes per day (2,500 tonnes / annum) with an average of 95% recovery rate and when operating at maximum capacity the system will produce 2.7 million litres of low sulfur, low emission fuel per year. The economic viability of the system is enhanced by the fact that the fuels produced are Excise-free, a saving of 38.4 cents per litre over refinery produced fuels. The capital costs of the system is approximately $3 M (What's New in Waste Technology, 2003).

2. Chemolysis

Chemolysis uses chemical agents as catalysts for complete depolymerisation of plastic resins into monomers or for the partial depolymerisation into oligomers, both of which can then be repolymerised to the original or new polymeric materials. Chemolysis includes a range of processes such as glycolysis, methanolysis, hydrolysis, saponification, diolysis and alcoholysis etc. However, glycolysis and methanolysis are more commercially proven than many of the alternative processes that are still undergoing research.

• Glycolysis is the partial depolymersiation in the presence of glycol such as ethylene glycol or diethylene glycol and breaks down polymers into monomers, which then must be blended with virgin monomer before repolymerisation. PET may be depolymerised to short chain polymers of just a few repeat units (oligomers). The material produced may be purified by melt filtration under pressure to remove physical impurities and be treated with carbon to remove chemical impurities.
• Methanolysis is the depolymerisation of plastic waste in the presence of methanol. It allows the use of a more contaminated feed of plastic waste than the glycolysis process but is more expensive. PET may be depolymerised to produce dimethyl terephthalate (DMT) and ethylene glycol (EG) by reaction with methanol, under pressure at around 200oC. DMT produced may be purified by distillation and crystallisation to give a high quality intermediate, which may be used to produce new PET. Once refined the EG may be used for a variety of applications, including antifreeze and PET production.
• Hydrolysis involves treating PET, for example, with water, acids or caustic soda to give terephthalic acid (TA) and ethylene glycol (EG), which may be repolymerised following purification. PET hydrolysis is less well commercially established than glycolysis or methanolysis.
• Saponification processes are being developed by 'Recopet' (France and Belgium) and United Resource Recovery Association (USA). Recopet is a multistage process where PET flakes are saponified, filtered and the dyes extracted. The process is reported to be less expensive than alternative chemical recycling methods because it uses relatively simple processing equipment (no pressure vessels) and inexpensive reagents. DKR commissioned a 6,000 tonnes/year PET bottle to bottle recycling plant in Rostock, Germany in 2000 to reprocess recovered bottles. The plant, operated by SKP Kunstoff Aufbereitung GmbH and Co., uses saponification to partially depolymerise PET pellets and remove surface contaminants.

Methanolysis, hydrolysis and saponification are able to remove at least some colour from coloured PET feedstock; glycolysis may not remove all the impurities and a certain amount of degradation and yellowing may occur. Glycolysis plants are frequently integrated with conventional PET production plants where the recovered BHET can be blended with new BHET to give the required end product quality. Glycolysis is most suited to recovered material of known history and high quality. Conversion costs of glycolysis may be less than those of methanolysis, since the intermediate formed is further down the PET production chain than produced by methanolysis. Feedstock recycling is, however, relatively capital intensive and has high operating costs and may only be commercially viable where comparatively large throughputs are possible. The competitiveness of feedstock recycling is continually improving as new technologies are developed.

5.4.5 Summary

It can be seen that a wide range of technologies developments are occurring with regards to the way in which plastic waste is reprocessed and reused. These significant technological advancements enable the products generated, after purification, to be identical to current feedstock and monomers used to produce new plastic materials. Thus these emerging technologies provide a diverse range of opportunities for reusing plastic wastes in addition to the more traditional mechanical reprocessing technologies currently employed (Plastic Resource, 2003).

5.5 Reprocessing Technology for PET and HDPE

In 2001 of the total plastic resins used in New Zealand, 45% were manufactured into food contact products. This primarily comprises PET and HDPE and in the same year 85% of PET and 38% of HDPE was used for food contact purposes. The most commonly collected polymers in New Zealand are PET and HDPE with a total of 4,772 and 5,736 tonnes respectively, collected in 2000. PET reprocessing is not considered economically viable in New Zealand at present due to low volumes and consequently there is no PET washline. However PET production and consumption is predicted to increase over the coming years and as kerbside collections systems and other waste minimisation initiatives mature increased diversion of PET can be expected. Technology for the processing of PET and HDPE is rapidly developing and an opportunity exists to reprocess PET and HDPE in the manufacture of food contact products.

5.5.1 PET

The production of food contact grade PET has the potential to a provide a high value market for all clear post consumer recycled PET, depending on reprocessing capacities and economics. Both applications usually require only clear or lightly tinted bottle feed due to the problems associated with achieving a consistent colour when using previously coloured PET. Markets for coloured PET recyclate are more limited; mechanically recycled flake retains its original colour and hence if the product is to be reused, markets must be found which can accommodate this.

In the UK, in addition to the manufacture of food and non food containers, the main end use markets for PET are staple fibre products, packaging in the form of A-PET sheet, strapping, chemical recycling, mixed plastic uses and incineration with energy recovery.

5.5.1.1 Containers (food-contact)

The on-going development of technology now enables 'closed loop' bottle-to-bottle recycling of PET. Legislation remains a significant factor affecting this market. PET bottles with a post consumer recycled plastic content were introduced in the United States in 1991 and have subsequently been used in a range of countries including Australia, New Zealand, Switzerland, Sweden and the UK. However, other countries including Italy and Spain, have yet to licence any processes for food contact grade PET.

5.5.1.2 Containers (non-food contact)

Whilst the specification / quality of recyclate required is high, specifications are not as demanding as those for food contact applications. Non-food contact PET container uses include bottles for detergent or household products which are frequently coloured, in such markets recycled PET may compete with virgin PVC, HDPE and PP.

5.5.1.3 Fibre Production

The PET recyclate fibre industry can be broken down into three divisions; staple, filament and spunbonded. Staple and filament fibres are similar products, but differ in length and are used in different applications. Staple describes fibres that are between 5 and 150 mm in length, with a thickness of 1 - 100 denier. Staple fibres are commonly used for 'fibre-fill' insulating material in products such as anoraks, duvets and sleeping bags. Filament fibre is a less significant market for mechanically recycled PET.

Filament is produced as a continuous length wound onto bobbins. The requirement for continuous fibres results in higher recyclate specification than 'staple'. The main end-use for filament are woven and knitted fabrics, home furnishings and industrial applications.

Spunbonded fabric is produced in a single extrusion step. Products produced generally high quality/value, applications such as geotextiles, shoe liners, roofing felts etc.

5.5.1.4 Packaging

Four main types of packaging product may be produced from post consumer PET bottle recyclate: amorphous-PET (A-PET) sheet, containers for food (multilayer), (single-layer) and strapping.

A-PET sheet is used in a variety of applications such as drinking cups, dairy boxes, vegetable / fruit punnets, boxes, lids, cartons, caps etc.

5.5.1.5 Strapping

Steel strapping is used in a wide range of demanding applications requiring strength, for example construction. Safety issues such as sharp edges and the effect of a sudden break under tension, have resulted in the widespread replacement of steel with other materials, including PET and PP.

Polypropylene is the lower cost alternative, however it can only be applied to less demanding functions, for example transit packaging. PET is the strongest of the plastic alternatives to steel, but is more expensive, which has limited its use in mass applications and restricted its use to those applications where strength is essential. PET has several significant advantages over steel: lighter in weight, non-rusting, cleanliness and the ability to heat-seal reducing binding time. Strapping requires recyclate with a very low level of contamination as well as a high, regular viscosity.

5.5.1.6 Mixed plastics

Mixed polymer applications are generally of relatively low value / tonne and hence, tend to take low quality mixed plastic feed. Whilst primarily polyethylene based (i.e. LDPE and HDPE) this feed may include some low quality PET. Mixed plastic intrusion moulding processes are generally limited in their ability to tolerate high levels of PET in their feed material as PET behaves as an inert filler.

Whilst it is conceivable that under certain limited conditions PET bottles may enter a mixed plastic recycling route, the inherent value of the recovered material is expected to support recycling via either mechanical or chemical PET recycling.

5.5.2 HDPE

HDPE bottles account for about 50% of the post consumer plastic bottles collected for recycling in the UK with approximately 6,000 tonnes of bottles collected during 2000. The main applications for post consumer HDPE are packaging products (e.g. blow-moulded bottles), extruded products (e.g. drainage pipe), sheet and film products (e.g. blown film bags, extruded film products), pallets and plastic lumber products.

As with PET reprocessing, mechanical recycling is unable to remove colour from feed material, hence uncoloured 'natural' HDPE can be used in second life applications where coloured HDPE may not be appropriate. For this reason natural HDPE commands a higher price than coloured HDPE.

• Packaging Products

HDPE recyclate may be used for a range of packaging products, including blow-moulded bottles, where multilayer extrusion is used to produce bottles with recycled HDPE sandwiched between layers of virgin HDPE.

5.5.2.1 Plastic wood products

Plastic wood products may be produced from single polymer feed (HDPE), mixed polymer feed and blends of polymers with other materials such as sawdust. The capital cost for this process is approximately $3 M and generally the greater the control over the feed material the greater the quality and consistency of the product and hence the wider the range of potential applications and the greater its value. Whilst the composition of plastic wood products vary, most employ a continuous phase of HDPE and LDPE. It is possible to produce plastic wood in a wide range of profiles allowing its use in applications such as gratings, fencing, compost bins etc. It is particularly well suited to outdoor applications where its low maintenance requirements can be a strong selling point, e.g. street furniture, animal pens, children's play areas etc.

Eaglebrook Plastics (Chicago, Il, USA) have produced plastic timber from post consumer dairy bottle feedstock since 1987. HDPE dairy bottles are ground into flake, air classified to remove paper contamination and then washed. The cleaned flake is compounded including foaming agents and extruded to give DurawoodTM. A large proportion of the plastic waste is recycled by this route, as sorting costs of low value plastic fractions, e.g. contaminated film and food packaging are prohibitive.

5.5.2.2 Food Grade Processes for PET and HDPE

Three approaches have been developed for the production of food grade PET and HDPE recyclate which include feedstock (or chemical) recycling, multilayer processing and superclean or (physical) recycling. Major European PET and HDPE reprocessors have been identified on the basis of their annual reprocessing capacity, using information supplied by PETCORE and the European Plastics Converters (EuPC) and are included in Appendix B.

5.6 Reprocessing Technology in the Wellington Region

Pacific Plastics, a firm located in Otaki, currently reprocess 1,100 tonnes per annum of mostly post industrial plastics and reprocesses it into over a 100 products that range from mats, buckets, flower pots, mud flaps, pipes to carpet cores and damp proof course material (Plastics New Zealand, 2003).

The company, which aims to sell all their products cheaper than the cost of virgin feedstock alternatives, currently exports products to Hong Kong, Australia, Singapore, USA and the UAE. It is estimated that the currently throughput could be expanded to a potential annual throughput of some 2,000 tonnes per annum if more modern machinery was procured. The company, which operate 12 hour shifts 6 days a week, currently employs 35 people from the local community, although it is envisaged that this would increase to 50 if the annual throughput was expanded to maximum capacity of 2,000 tonnes per annum.

The company currently processes a range of polymers that are collected from kerbside collection and drop off sites from local authorities across the region from New Plymouth and Napier down to Wellington and South Wairarapa. The material is collected from commercial companies such Full Circle and SMART Recyclers who operate kerbside collection service and recycling centres where the material is bulked up and bailed. Some of the material arrives at the plant pre-sorted into the various polymers and is ready to start the reprocessing procedure. This saves Pacific Plastic valuable resources and time in carrying out manual sorting. More recently 30 tonnes a month of chipped HDPE is purchased and transported from SMART Recyclers in Auckland and transported to the Otaki plant for reprocessing. It is more cost effective to transport the chipped material than to manually segregate the voluminous commingled material collected from the Wellington region. It might be beneficial for regional recovery rates if there was a greater level of sorting, chipping and so that transport costs may be reduced.

The range of resins reprocessed include HDPE (2), LDPE (4) and PP (5), all of which are processed at the plant through injection and extrusion processes and converted into product such as buckets and flower pots, for example. In addition HDPE (2) and LDPE (4) are also combined and processed by sheet extrusion to make mud flaps for horse floats. LDPE adds flexibility while HDPE has more rigid characteristics. In addition HDPE (2) and LDPE (4) are also processed individually by extrusion to produce underground pipeline, pipes and carpet cores, for example. The ducting, which is 6 m in length and 110 mm in diameter are sold in packs of 54, which take 12,500 2 L milk containers to produce. PP (5) however is primarily processed through injection moulding, while PVC is purchased in 10 tonne consignments from a company that strips the PVC coating from wire. That is then processed and converted to black mats. In addition carrier bags are also processed by extrusion to produce black sheeting, while investigations are currently underway to establish if processing of film generated from the agricultural sector can be introduced. The limiting factor to processing this material is the removal of contaminants such as straw, that effect the manufacturing process and the quality of the product. Investigations have also been undertaken into suitable machinery for processing commingled plastics that would alleviate the problem of contamination of mixed resins. It appears however that the capital investment required would be in excess of $1M.

In addition to the above, a small quantity of PET (1) is required to be collected from Kapati Coast District Council. However no PET processing plant exists in New Zealand due to the low volumes being generated and the lack of a PET washline. The material collected is therefore landfilled or exported to Asia for reprocessing and reuse in textiles.

Pacific Plastics are manufacturing a wide range of products and making a significant contribution to the plastic reprocessing capacity of the Wellington region. It remains that throughput could be further increased given appropriate investment in more modern machinery. The barriers to increasing the reprocessing capacity of the company are predominantly associated with the age of the machinery and constant maintenance requirements. While improvements could be made with regards to the supply of semi-processed material and more efficient sorting techniques, it is investment in machinery that is the limiting factor to expansion. To this end the company are looking to develop a joint venture opportunity to invest in the necessary equipment to increase throughput and to obtain semi-processed feedstock. In addition to the company's efforts to advance plastic reprocessing in the region, councils could also play a significant role by raising the profile of Pacific Plastics through actively promoting the range of products made from recyclate collected from the residents across the region. This would potentially lead to increased sales and improve public awareness and participation in local recycling schemes.

If the projected increase in plastic production and consumption continues a greater proportion of plastic will be present in the commercial and residential waste streams. As more sustainable waste management practices are adopted and waste minimisation targets achieved an increased quantity of plastic will be diverted from landfill, thus an expansion in the reprocessing capacity in the Wellington regions and across New Zealand will be required. It seems that Pacific Plastics could make a significant contribution to the reprocessing capacity of the Wellington region given appropriate investment and support in sorting and processing infrastructure.

5.7 Summary of the Options Available for the Reprocessing of Plastic in the Wellington Region

A template has been formulated to summarise and assess the options available for the reprocessing of plastic in a given region across New Zealand. The template, which is included in Appendix A, has been used to assess the development of a reprocessing sector for plastic in the Wellington region and is included overleaf. The shaded area depicts information on various technologies which applies everywhere in New Zealand. Conversely, the non shaded area (Barriers to Regional Suitability), varies across New Zealand and has to be determined for each study region taking into account factors such as distance to reprocessors, existing regional reprocessing infrastructure, transport costs and volumes, for example.

The template for the Wellington Region includes information relating to the capital investment required to procure the various technology options and the minimal viable scale needed to operate each facility or process. Where this data has not been available specific information relating to a actual, planned or commissioned plant has been used. The end products of each option are included and whether the technology is under development or available as a proven process applied in New Zealand and / or overseas. An assessment and generic rating system of low, medium and high has been applied to the individual Economic Sensitivities and Risks, with low (white circle) indicating minimal cost or risk, whereas high (black circle) indicates significant cost or risk. The categories considered under Economic Sensitivities and Risks include:

• Entry Cost - capital or other investment required to establish each process
• Transport Costs - cost of transporting the plastic waste to the reprocessor. As plastic is light and often un-baled, transportation costs are generally considered high.
• Product Demand - actual demand or potential market for the product
• Feedstock Quality - the degree of polymer sorting required for each technology
• Technology Development - small scale trials or widely used proven technology
• Volume Dependent - minimum process throughput required for operation