Little is made of trying to use less concrete in industry net zero plan
The concrete industry’s roadmap to carbon zero lays out its plans to clean up what is one of the world’s largest polluters but glazes over the idea of simply using less concrete.
The cement used in concrete is responsible for about 8 percent of the world’s greenhouse gas emissions, with one tonne of cement producing as much as 800kg of carbon emissions.
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Barbara Nebel, chief executive of thinkstep-anz, the sustainability consultancy responsible for the roadmap, said it allows for a 44 percent decrease in emissions from 2020 levels by 2030 and net zero carbon by 2050.
The plan for the period to 2030 relies on alternative fuels and increasing the use of mineral additions with a lower footprint than cement.
Between 2030 and 2050, the industry's main plan is to use carbon capture technology, which it hopes will make up 34 percent of the 100 percent reduction by 2050.
Concrete usage
According to Stats NZ figures released yesterday, annual concrete volumes are now sitting at the lowest point in two years, after a burst of stronger activity up until mid-2022.
Infometrics economist Sabrina Swerdloff said the pace of concrete production declines was beginning to slow, falling just 0.4 percent in the June quarter (adjusted for seasonal effects), compared with declines of more than 2 percent in the past four quarters.
Swerdloff said with just one-quarter of data showing improvement, it was too early to say if concrete production would begin to stabilise.
Ready mix concrete production is a popular micro-economic indicator of actual building activity (consents indicate an intention to build), and the consensus seems to be that the current lull represents a softening in residential construction.
At face value, the concrete roadmap and Stats NZ data are related by material only, but the timing of the Stats NZ figures coinciding with the concrete industry’s 2050 roadmap did raise a question about why the report didn’t address the most basic of ideas around reducing its carbon footprint – using less of it.
Not building
New Zealand Green Building Council chief executive Andrew Eagles is obviously supportive of any improvements in the embodied carbon of construction materials but is keen to point out that “not building” is often a good option.
He referenced the University of Auckland’s Building 201 project which gained a six Green Star rating, the highest rating since the green building council introduced the certification.
Originally a brutalist concrete building built in the 1970s, when the project is complete in 2024, the existing concrete structure will be retained and wrapped with a curtain wall system, which Eagles said saved huge amounts of embodied carbon.
Speaking on the project in August last year, Beca associate environmentally sustainable design engineer Timothy Howarth said he hoped it would become an inspiration for other projects.
“There’s no reason why Aotearoa’s existing building stock can’t be brought up to modern standards with the right care and attention. The world only has a limited carbon budget and making better use of our existing buildings and aging building stock is a great way to lighten our footprint.”
Asked why the concrete industry decarbonisation report didn’t address reducing reliance on concrete, Concrete NZ chief executive Rob Gaimster said population growth and urbanisation meant there would be greater demand for concrete no matter what, “but that’s going to be decarbonised concrete”.
“If you think about climate change, and adapting to climate change, coastal defences, sea walls, whatever, we're gonna need more durable materials, not less durable materials.”
Gaimster said the organisation fully supported the reuse of building structures where possible, though it wasn’t featured in the report.
“That's the first thing you do when you look at what to do with the current building, you know, can it be repurposed?”
He said it was the very nature of concrete that made structures reusable, “Concrete buildings can be repurposed because they're just so durable and they can go on for many decades to come.”
Climate credentials
Eagles said as developers are increasingly pressured to up their green credentials, materials are going to come under greater scrutiny.
“Developers are starting to say, how can we look at wood or green concrete or what steel is doing? Should we be moving away from steel to wood? Should we look at how we're constructing with an emphasis on using existing structures.”
He said if the concrete industry were successful in finding a material reduction in its carbon footprint through using pozzolans instead of cement, where the bulk of concrete’s carbon footprint is generated.
“Real reductions by 2030 is going to keep them in the game as the material because otherwise, people are going to look to other products.”
Wood advocate and Red Stag chief executive Marty Verry said though concrete would always have a place in floor slabs and horizontal construction, he didn’t see what benefits it had next to cross-laminated timber, which his firm produces.
Verry was particularly critical of relying on unrealistically expensive carbon capture technology and talk of pathways to 2050, without making major gains in this decade.
“Do we have the leisure of waiting and hoping for cement to get there by 2050, or just build in negative-emission materials now?”
