Asphalt gobbler turns road work into recycling magic

6:39 am on 17 December 2022

As many Kiwis prepare to hit the road for summer, Waka Kotahi's getting ready for its regular holiday schedule of road resurfacing.

Work will be carried out on about 10 percent, or 2450 lane kilometres, of the country's state highways.

But what happens to the old road seal when new asphalt is laid on?

One of the nation's biggest construction contractors Fulton Hogan has a new machine to deal with the leftovers in a more environmentally friendly way.

Their Belgian-designed mobile asphalt crusher was the first fully electric model in Australasia.

Fulton Hogan's mobile asphalt crusher was the first fully electric model in Australasia.

Fulton Hogan's mobile asphalt crusher is the first fully electric model in Australasia. Photo: RNZ / Tom Taylor

Transport Minister Michael Wood described it as a "win-win-win": creating less waste, recycling materials, and saving money in the process.

"We know that we've got a big challenge in our system to decarbonise transport.

"Some of that's about what we build, but it's also about how we build it."

High-traffic roads like state highways needed resealing about every seven years, requiring a lot of asphalt every time the maintenance roster rolled around.

"This enables us to have approximately 30 percent recycled product in some of the roads that we're laying down around the country," Wood said.

Transport Minister Michael Wood.

Transport Minister Michael Wood. Photo: RNZ / Tom Taylor

"So that's a huge step-up in terms of our ability to take something that otherwise might have been a waste product and use the value of it to build and maintain our roads."

Waka Kotahi was critical of Fulton Hogan's State Highway 1 resealing work in Dome Valley, which saw chipseal coating weekend travellers' tyres.

However, Wood said there were lessons to be learned from the failure.

He said the roading network was coming under increasing pressure from climate change, with regions like Northland, Nelson-Marlborough, and the East Cape already dealing with the repercussions.

"From government and Waka Kotahi, we're doing a lot of work on how we make sure that we build a more resilient network, but we're going to have to do a lot of work to make sure we keep on top of that.

"It is going to require more investment in the future, but it's also a good reason to be making sure that we do what we can to reduce our emissions and prevent climate change from becoming even worse."

The Belgian-designed mobile asphalt crusher in action.

The Belgian-designed mobile asphalt crusher in action. Photo: RNZ / Tom Taylor

Fulton Hogan's new machine ticked some of these boxes, saving an estimated 80 tonnes of carbon dioxide emissions each year.

It also saved about $55,000 a year on diesel costs.

Savings which would be passed on, the company's Auckland regional manager James Weller said.

"It's a lot cheaper to run, and that flows through our whole process to the end-product and to our customers."

Weller said the machine was the kind of capital investment that was needed to reach the company's carbon reduction targets.

Fulton Hogan aimed to have a 30 percent emission reduction on its 2021 baseline by 2030, and become net carbon zero by 2050.

New Zealand company Equip2 supplied Fulton Hogan with the machine.

Its general manager Ben Hart said the electric crushers produced about 60,000 tonnes of recycled asphalt a year, creating what he called a "circular economy".

But with just 30 percent recycled material currently going into the mix, Hart said there was work to be done to get it up to 100 percent.

"With New Zealand, we use about 9-10 tonnes of aggregate per person per year. That's a lot.

"It's something we don't actually think about, but it's going into our houses, industries, roading, infrastructure, technology, even healthcare.

"It's awesome to know that it's getting reused again, and it's also de-risking and lowering the emissions."

Hart said New Zealand companies could look to their European counterparts as world-leaders in recycling roads, and continue driving towards their target of giving all materials a second life.

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