Aaron Currie in front of Bullocks' silos on Taupō Quay. Photo / Mike Tweed
Whanganui concrete companies are pushing for greater sustainability, but there is “not one silver bullet” to reach carbon net zero.
Bullocks Whanganui supplements its general-purpose cement (GP) with Eco-Max, made from blast furnace slag, a by-product of the steel industry.
“In a nutshell, a lot of cement is made using heat, and that uses a lot of energy,” director Willy Morrell said.
“The dehydration process releases a lot of carbon dioxide.
“If you can use a waste by-product in its place, it’s a really easy saving.”
He said using eco-concrete instead of GP saved 60kg of carbon emissions per cubic metre.
“That doesn’t sound like a lot, but it’s basically the same as one person flying from Whanganui to Auckland.”
In 2023, Bullocks secured a $463,000 grant from the Energy Efficiency and Conservation Authority’s Low Emission Transport Fund, which it matched to buy two electric front-end loaders.
Morrell said the company decided to “go all in” when it came to sustainability.
A new plant at Bullocks’ Taupō Quay site cost about $2 million.
“We’ve put in solar panels, and since last week, we’ve been recycling the water that washes out the bowls of our trucks,” he said.
“It goes back into the production system, making concrete.”
Bullocks general manager Aaron Currie said there were two silos at Taupō Quay, for general-purpose cement and Eco-Max, and the two were mixed to match clients’ specifications
“We can go up to 60% or 70% (Eco-Max), and there are players in Auckland who do that,” he said.
“Even new (residential) builds are asking for it. Some people want as much carbon reduction as possible, down to composting toilets.”
Concrete NZ sustainability and policy director Tim Kleier said using blast furnace slag was not a new idea.
“Where I’m from, in Germany, people started using it in the 1870s," he said.
“They were mocked by their colleagues, but in the 1920s, slag cement was labelled equivalent to normal Portland cement from a performance perspective.
“From there, it really started supercharging.”
Bullocks is supplied by HR Cement.
Kleir said Concrete New Zealand had a goal of reaching carbon net zero by 2050, and that required “seven levers”.
Carbon net zero is achieved when greenhouse gas emissions and removals from human activities are balanced.
“There is not one silver bullet that will deliver everything to us, but there are a whole slew of things we can do,” he said.
“An important lever is the uptake of SCMs (supplementary cementitious materials), like what Bullocks is doing, and another is electrification.”
Perceptions remained around low-carbon concrete - “everyone expects it’s going to cost a lot more”, he said.
“It is mostly determined by supply chain costs, but in urban centres, where 80% of concrete is placed in NZ, it will be cost-neutral.”
McDonald Concrete manager Ross McDonald said his company had begun to use blast furnace slag as a cement supplement, supplied by Holcim.
“Obviously, it’s better for emissions, but it’s also less reactive with chemically aggressive environments, like wastewater pipes,” McDonald said.
He said sustainability and emission reduction were key factors when councils and Government agencies awarded contracts.
“It could have been why we got the tick for the Ōtaki to north of Levin job. We’re working with Fulton Hogan on the northern portion.
“That’s an amazing thing for Whanganui, to supply national jobs, and it’s work secured for the next two to three years.”
Construction began on a 24-kilometre stretch of State Highway 1 from Ōtaki to north of Levin last September.
The four-lane highway should be finished by 2029.
Morrell said once the NZ concrete industry was committed to a low-carbon future, it would be easy to catch up with the rest of the world.
“It’s not like we have to reinvent everything. It’s all there.
“We just have to pull in those lessons earned from abroad and integrate them into what we’re doing.
“If you end up with a better product and it doesn’t cost more, it’s a no-brainer.”
Mike Tweed is a multimedia journalist at the Whanganui Chronicle. Since starting in March 2020, he has dabbled in everything from sport to music. At present his focus is local government, primarily Whanganui District Council.