KEY POINTS:
Thousands of tonnes of plastic leaves kerbsides each year but the journey doesn't end at the processing stations around Auckland.
Some is recycled and reused in New Zealand, and some is sent to places like China, Hong Kong, Taiwan and Vietnam.
But not all councils accept all seven grades of plastics for recycling. The reason for that is as much about economics as it is about environmental consciousness.
While Auckland and Manukau City Councils accept all grades, Waitakere and North Shore cities will receive only type 1 and 2 plastic bottles in their wheelie bins.
"We were aware when many councils moved to collecting 3s to 7s that a lot of this stuff was going back to China and being used in incineration plants," said Jon Roscoe, Waitakere City's solid waste manager.
"It was cheaper than coal and it had a higher calorific value.
"Unless we had some form of warranty from who our contractor was selling them to, we were very reluctant to actually extend to that area.
"We're looking for local uses, but at the moment there is a very high demand for it in China and they're paying a lot of money for it. So you can't ignore that.
"If you're having a slight environmental compromise to raise funds to support other activities you do, it certainly makes sense. There's not much you can do environmentally without money."
But these markets are unstable and slight fluctuations in exchange rates can see the demand for plastics from New Zealand shrivel to nothing - leaving councils with mountains of plastics with nowhere to go.
In North Shore, approximately 0.5 per cent of the 1500 tonnes of plastics put out for recycling each year are not accepted by the council. But they are recycled as well.
North Shore's waste contracts officer, Nic Quilty, said Onyx, which collects for North Shore and Waitakere, is able to find overseas markets for these plastics - for now.
"It is all recycled but we are not certain and are not satisfied that the market overseas is secure."
The type 1 and 2 plastic bottles, meanwhile, are sold to a recycling company in New Zealand.
But the plastics that do get recycled represent a tiny fraction of the total that could be reused. An audit in 2006 found plastics made up around 13.6 per cent of the total contents of a typical household rubbish bag. Translated, that means 3000 tonnes out of the 22,550 that heads to landfills from North Shore households are plastics that could potentially be recycled.
Ms Quilty accepts that more of this could be prevented from filling up landfills and expects the council to be able to recycle more in future.
Auckland City Council's manager of recycling and waste minimisation, Warwick Jaine, said around 300 tonnes of waste to landfill comprises plastics that can be recycled.
The council, with Manukau, accepts all seven grades of plastics for recycling.
Mr Jaine said the council was aware of the issues surrounding the reuse of plastics overseas and was confident with its contractor Streetsmart selling them to "reputable markets".
Things will improve even further in July, he said, when residents in the two cities switch to a new 240-litre bin for all recyclable materials.
New contractor Visy is a major recycling firm with connections to more markets. The materials will be collected fortnightly and sorted at a new purpose-built station in Penrose.
It will be the largest and most technologically advanced in the Southern Hemisphere, doing away with manual sorting.
HOW PLASTIC IS REUSED
GRADE 1 PET (Polyethylene terephthalate)
* Typically fizzy drink, water and juice bottles, some shampoo and detergent bottles.
* Spun into yarn to be made into clothing, carpets and part of polar fleece jacket linings.
GRADE 2 HDPE (High-density polyethylene)
* Typically milk bottles, household cleaner and dishwashing detergent bottles.
* Manufactured into a range of products including pipes, matting, slip-sheets, buckets and compost bins.
GRADE 3 PVC (Polyvinyl chloride)
* Detergent bottles, some shampoo bottles, wrapping film.
* Can be made into drainage pipes, traffic cones, fencing, house siding, tiles, handrails, and hoses.
GRADE 4 LDPE (Low-density polyethylene)
* Bread bags, trash bags, film for sacks.
* Recycled into the same items.
GRADE 5 PP (Polypropylene)
* Bread bag tags, jars, some wrapping film, icecream containers.
* Recycled into auto parts, auto battery cases, bird feeders, pails, furniture and industrial fibres.
GRADE 6 PS (Polystyrene)
* Yoghurt and margarine containers, meat trays, hot and cold drink cups.
* Recycled into insulation board, packing peanuts, office and desk accessories, waste baskets, videotape cassettes and reusable cafeteria trays.
GRADE 7 All other resins and mixed plastic
* Plastic plates and cups.
* Difficult to recycle but typically re-used in automotive and other durable goods.
