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Large forest products company Pan Pac north of Napier where treated timber is proposed to be burnt. Photo / NZME

A Hawke's Bay mill plans to burn treated timber waste in one of its large boilers north of Napier, in a move which will be closely monitored for possible health risks.

Funding has been secured for a trial which will look at diverting treated timber from landfill before burning it in one of Pan Pac Forest Products' existing boilers at Whirinaki.

The project has the support of Hastings District Council and Hawke's Bay Regional Council as well as $40,000 in funding from the Government's Waste Minimisation Fund.

If the upcoming trial is successful there are plans for at least 14,000 tonnes of treated timber to be burnt each year at the site, to prevent it ending up in landfill and generate energy for the Pan Pac plant.

"We expect the boiler's existing emission management system will manage any contaminants/pollutants but we are essentially doing the trial to ensure that burning treated timber is a safe long-term option," Pan Pac environmental manager Reece O'Leary said.

Some chemicals used in New Zealand to treat timber are toxic, including arsenic, which is a key component in a commonly used treatment known as CCA.

Some councils across the country ban residents from burning treated timber on household fireplaces as a result.

O'Leary said the treated timber for the project was not coming from Pan Pac itself, but rather "councils, waste management companies and construction and demolition companies" from across the region.

It will include the likes of off-cuts from new building work and demolition waste from old structures.

Under the proposal, companies disposing of treated timber will not be charged by Pan Pac to use the boiler.

"Pan Pac does not produce any treated timber products," O'Leary said.

"There is limited benefit to Pan Pac, but significant benefit to the Hawke's Bay community.

"Treated timber is a problematic waste stream that councils are struggling to manage as a result of an increase in construction and demolition over recent years."

Pan Pac currently burns about 30,000 tonnes of "community waste" in its two boilers to generate energy for the plant.

"The treated timber initiative is essentially an extension of that existing waste diversion offering that is already in place.

"Companies pay nothing for the service, avoid landfill fees and the environment wins because the material is kept out of the landfill."

A consent is required from Hawke's Bay Regional Council (HBRC) to undertake the trial and Pan Pac is "working through the process" with the council at present.

An air-quality expert will supervise the trial and will review the results of air emission testing. Ash from the boilers will also be tested to check for levels of contaminants.

HBRC regulation and policy group manager Katrina Brunton said they supported the trial, but were waiting on a consent application to be lodged.

"Should an application be lodged, conditions would be attached to that consent requiring all air discharges to be monitored and reported to HBRC.

"The council would work with Pan Pac to monitor the conditions of consent.

"As with any consent holder, if the consent holder is in breach of consent conditions, they would need to take action to amend the activity within the trial to ensure conditions are met."

A Hastings District Council spokesperson said the project aligned with its goal of 30 per cent total tonnage decrease in organic waste to landfill by 2024.

Timber classified as H1.2 to H5 will be burnt in the boiler under the current proposal, which includes timber treated with chemicals such as CCA.

Most building timber is treated with preservatives or chemicals to stop the wood from rotting and to protect it from burrowing insects.