The country's main centre mayors have told the Government they are keen to look at the benefits of processing all recycled paper and cardboard onshore.

Auckland Mayor Phil Goff wants a study on the cost of processing all of New Zealand's recycled paper and cardboard onshore, asking for taxpayer cash to help fund the work.

A letter to Associate Environment Minister Eugenie Sage, released to Stuff on Wednesday, is also signed by Christchurch Mayor Lianne Dalziel and Wellington Mayor Justin Lester.

Goff, Dalziel and Lester are keen to commission a feasibility study "to explore the costs and benefits of establishing the capacity to process all of New Zealand's recycled paper and cardboard onshore".

Currently, some cardboard and paper is made into end products in New Zealand, but a "significant quantity" goes to Asia.

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The letter shows paper and cardboard now account for nearly half of all kerbside collections in Auckland and Wellington, at 46 per cent. In Christchurch the materials make up 41 per cent of collections.

ANDY JACKSON/STUFF Associate Environment Minister Eugenie Sage has said New Zealand needs more onshore recycling and processing plants.

However, the market for the recyclables had collapsed with "no evidence of a recovery", the three mayors wrote.

The market price collapse was largely due to China's National Sword programme, which had seen the country restrict imports of waste products.

Goff, Dalziel and Lester want the Government to help their councils pay for the study.

JASON DORDAY/STUFF Auckland Mayor Phil Goff, who signed the letter, which asks for Government cash to fund a study looking at processing all recycled paper and cardboard in New Zealand.

The letter shows the three councils, along with other local bodies, were "experiencing significant challenges" to minimise waste.

"Securing a sustainable solution for the management and processing of this product is a critical element of the comprehensive suite of measures we need to maintain New Zealand's progress in waste minimisation," it reads.

"While some recycled paper and cardboard is processed into end products in New Zealand, a significant quantity is shipped to Asia for processing.

"Our continued reliance on offshore processors creates significant vulnerability, as we have experienced with China's change in policy."

The mayors' letter follows a remit passed at July's Local Government New Zealand conference calling for an increase to the $10 levy the charged per tonne of rubbish dumped at landfills. The change was pushed by Wellington, seconded by Christchurch and strongly supported by Auckland.

Sage has previously said New Zealand needed more onshore recycling and processing plants – and that they required sufficient supply and demand to be commercially viable.

GEORGE HEARD/STUFF Christchurch Mayor Lianne Dalziel, another signatory of the letter to Sage.

The Government's long-term effort was focused on improving onshore processing capacity for recyclable materials.

It was working with councils and waste management companies and could continue to support the development of recycling facilities through the Waste Minimisation Fund, Sage said.

But Goff, Dalziel and Lester were critical of councils taking their own approach to collection, processing and disposal.

ROBERT KITCHIN/STUFF Wellington Mayor Justin Lester. Paper and cardboard accounts for 46 per cent of residential kerbside collection in the city.

"This has created a fragmented response to waste management that misses out on economies of scale, and means that many communities have poor access to recycling services," they wrote.

"Any successful strategy to address the existing patchwork model urgently needs leadership and guidance from central government."