An increasing amount of biodegradable plastic is being imported into New Zealand which could eventually contaminate the recycling of standard plastics.

Alan Fernyhough, Scion biomaterials engineering unit leader, said bioplastics made up just 1 per cent of plastics but the growth rates were 15-20 per cent.

They were marketed as biodegradable and compostable but they did not always end up that way.

Facilities like high-temperature commercial composters did not exist in New Zealand, he said.

Mr Fernyhough said because the volume of bioplastics was small there was no drive yet to separate them for recycling from other plastics but the time would come.

Bruce Gledhill, chairman of Recyclers of New Zealand, said bioplastics could contaminate mainstream plastic recycling if the volumes grew enough.

Mr Gledhill said such PLA plastics, made from plant starches, could be sorted using infra-red lighting but no one was doing that and they were otherwise difficult to detect visually.

Mr Gledhill said there was already confusion about what could and couldn't be recycled because different councils had different rules.

A lot of recyclable plastic could not be recycled as it was compounded with plastic that was not recyclable, he said.

Tony Nowell, chairman of the Packaging Accord governing board, said overseas demand for degradable plastics and packaging using recycled content was having an impact on the domestic market place.

"Yet degradable plastics are non-recyclable in New Zealand because the infrastructure is not in place to deal with it.

"As small players on the world stage we are the recipients of choices which other countries make about packaging."

Mr Nowell said packaging imports now made up about 50 per cent of local consumption.

Grant Hall, chief executive of Good Water, said contamination was a red herring because the volumes of PLA plastic were so low.

Mr Hall added that plastic was not recycled into new clear bottles in New Zealand, but if they were and there was contamination it would only create a haze.

Good Water used PLA bottles made from corn, a renewable source, and the company attempted its own recycling scheme through swap-a-crate systems and recycle bins at big events.

Mr Hall said the plastic was blended with other material and used to make underground cable covers.

By Angela Gregory Email Angela