How a Marlborough sawmill cracked the code on timber’s waste problem

Every year, around 400,000 tonnes of treated timber waste ends up in New Zealand landfills. Much of this is timber treated with copper, chromium and arsenic (CCA). But what if the solution isn’t about managing this waste better, but preventing it altogether?

A Marlborough sawmill is showing how the industry can break this cycle by combining arsenic free timber treatment, with renewable energy generation. It’s an approach that turns the traditional waste-to-landfill model on its head.

“New Zealand’s construction and agricultural sectors have been grappling with this issue for decades,” says Sam Lees, Sales Manager at OneFortyOne Kaituna Sawmill. “With MCA treatment, we have a practical solution that works for everyone.”

The shift centres on micronised copper azole (MCA) treatment – a copper-based preservative without arsenic. MCA timber is a tried and true solution that offers the same resistance to decay and mould as traditional treatments but opens up possibilities that CCA never could. Most significantly, it can be safely burned in Kaituna’s biomass boilers. This changes everything – it means timber offcuts and end-of-life MCA timber are now being repurposed in a boiler that runs on wood to create renewable energy.

“Because MCA doesn’t contain arsenic, it changes the whole equation around disposal,” Lees explains. “Material that would’ve ended up in landfill now gets a second life, helping power our operations.”

The sawmill has resource consent to include MCA-treated timber waste in its biomass fuel – combining it with sawdust and other wood residues to generate energy for kiln drying, creating a closed-loop, circular economy approach.

Local builder Mark Thompson has seen the difference firsthand. “We’ve been using Kaituna’s MCA timber on decks and outdoor projects, and it’s really changed how we think about waste,” he says. “As builders, we generate a lot of timber offcuts, and honestly, it never felt great just dumping it all in landfill.”

The environmental benefits have become a selling point with clients. “Now I can tell families that our waste timber goes back to Kaituna and gets turned into clean energy instead of rotting in a tip somewhere,” Thompson says.

The practical benefits matter too, he says. “The offcuts get collected at no extra cost to us or the client. It’s doing the right thing environmentally without any financial penalty, which is pretty rare in construction these days,” Thompson says.

The shift is already making waves in the viticulture industry, where approximately 500,000 vineyard posts are replaced in Marlborough each year, many of which are currently dumped in landfills.

Beyond vineyards, MCA-treated timber is gaining traction in residential and commercial construction. It qualifies for points under green building certifications like Green Star and Homestar, giving builders, developers and homeowners an alternative that doesn’t compromise efficacy or performance.

For Lees, the next step is about shifting industry and consumer demand. “We’re seeing more builders and merchants asking about alternative timber options,” he says. “It’s about recognising that every project decision makes a difference – for our customers, our communities, and the environment.”